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Lots of slide tweaks to work nicely on my 1024x768 laptop
[gitmo/moose-presentations.git] / moose-class / slides / index.html
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3<html xmlns="http://www.w3.org/1999/xhtml">
4
5<head>
6<title>Introduction to Moose</title>
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40<div id="header"></div>
41<div id="footer">
55906a14 42 <div id="license">
debc93f8 43 <a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/us/"><img alt="Creative Commons License" style="border-width:0" src="ui/creative-commons.png" /></a>
7167c54d 44 <br /><span xmlns:dc="http://purl.org/dc/elements/1.1/" href="http://purl.org/dc/dcmitype/Text" property="dc:title" rel="dc:type">Introduction to Moose</span> by <span xmlns:cc="http://creativecommons.org/ns#" property="cc:attributionName">David Rolsky</span> is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/us/">Creative Commons Attribution-Share Alike 3.0 United States License</a>.
55906a14 45 </div>
46
b751d33f 47 <h2>Introduction to Moose</h2>
48</div>
49</div>
50
51<div class="presentation">
52
53<div class="slide">
54 <h1>Introduction to Moose</h1>
17d7a564 55 <h2><a href="git://git.moose.perl.org/moose-presentations.git"><tt>git://git.moose.perl.org/moose-presentations.git</tt></a></h2>
b751d33f 56</div>
57
58<div class="slide">
59 <h1>Moose Summed Up</h1>
60
61 <ul>
62 <li><strong>Declarative</strong> OO sugar</li>
63 <li>Introspectable</li>
8d1ce1d7 64 <li>Extensible (MooseX::* on CPAN)</li>
b751d33f 65 </ul>
66</div>
67
68<div class="slide">
55906a14 69 <h1>Moose Background</h1>
b751d33f 70
71 <ul>
55906a14 72 <li>Created by Stevan Little, first released in 2006</li>
b751d33f 73 <li>Moose builds on Perl 5's native OO</li>
74 <li>Borrows ideas from other languages, notably Perl 6</li>
75 <li>Provides semantics for common operations</li>
76 </ul>
77</div>
78
55906a14 79<div class="slide fake-slide0">
80 <h1>Part 0: Moose Concepts</h1>
81</div>
82
b751d33f 83<div class="slide">
84 <h1>Classes</h1>
85
86 <ul>
87 <li>
88 Classes have ...
89 <ul>
90 <li>Attributes</li>
91 <li>Methods</li>
92 <li>Superclasses</li>
93 <li>Method modifiers</li>
94 <li>Constructor and destructor</li>
95 <li>One metaclass object</li>
96 </ul>
97 </li>
98 <li>Classes do roles</li>
99 </ul>
100</div>
101
102<div class="slide">
103 <h1>Class Example</h1>
104
105 <pre><code>package Person;
106<span class="highlight">use Moose;</span></code></pre>
107
108 <ul>
109 <li>Poof, a Moose-based class!</li>
110 </ul>
111</div>
112
113<div class="slide">
114 <h1>Attributes</h1>
115
116 <ul>
117 <li>Aka property, slot, field, member variable</li>
118 <li>A piece of data owned by an object</li>
119 </ul>
120</div>
121
122<div class="slide">
123 <h1>Attributes</h1>
124
125 <ul>
126 <li>
127 Attributes have ...
128 <ul>
362c7c75 129 <li>Mutability (read-only vs read-write)</li>
b751d33f 130 <li>An optional type</li>
131 <li>Accessor methods</li>
132 <li>Delegation methods</li>
133 <li>Optional default value</li>
134 <li>Many more features</li>
135 </ul>
136 </li>
137 <li>Stored in the object, but don't worry about that</li>
138 </ul>
139</div>
140
141<div class="slide">
142 <h1>Attribute Example</h1>
143
144 <pre><code>package Person;
145use Moose;
146
55906a14 147<span class="highlight">has first_name =&gt; ( is =&gt; 'rw' );</span></code></pre>
b751d33f 148
149</div>
150
151<div class="slide">
152 <h1>Methods</h1>
153
154 <ul>
155 <li>Nothing fancy here, just Perl subroutines</li>
156 </ul>
157
158 <pre><code>package Person;
159use Moose;
160
161<span class="highlight">sub greet { ... }</span></code></pre>
162</div>
163
164<div class="slide">
165 <h1>Roles</h1>
166
167 <ul>
168 <li>Classes <strong>do</strong> (or consume) roles</li>
169 <li>Similar to mixins and Java interfaces</li>
170 </ul>
171</div>
172
173<div class="slide">
174 <h1>Roles</h1>
175
176 <ul>
177 <li>Like classes, can have attributes, methods, do roles</li>
178 <li>Roles can require methods</li>
179 <li>Roles are composed (flattened) into classes</li>
180 </ul>
181</div>
182
183<div class="slide">
184 <h1>Role Example</h1>
185
186<pre><code>package HasPermissions;
187<span class="highlight">use Moose::Role;</span>
188
189has is_admin =&gt; ( is =&gt; 'rw' );</code></pre>
190</div>
191
192<div class="slide">
193 <h1>Role Example</h1>
194
195 <p>
196 And then ...
197 </p>
198
199<pre><code>package Person;
200use Moose;
201
202<span class="highlight">with 'HasPermissions';</span></code></pre>
203</div>
204
205<div class="slide">
206 <h1>Method Modifiers</h1>
207
208 <ul>
209 <li>AKA advice</li>
210 <li>&quot;<strong>Before</strong> foo(), do this first&quot;</li>
211 <li>&quot;Do this <strong>after</strong> foo()</li>
212 <li>&quot;Put this code <strong>around</strong> foo()&quot;</li>
213 </ul>
214</div>
215
216<div class="slide">
26164c8d 217 <h1>Before and After</h1>
b751d33f 218
219<pre><code>before 'foo'
220 =&gt; sub { warn 'About to call foo()' };
221
222after 'foo'
223 =&gt; sub { warn 'Leaving foo()' };</code></pre>
224
225</div>
226
227<div class="slide">
228 <h1>Around</h1>
229
230<pre><code>around 'foo' =&gt; sub {
231 my $real_foo = shift;
232 my $self = shift;
233
234 warn 'Just before foo()';
235 my @return =
236 $self-&gt;$real_foo( @_, bar =&gt; 42 );
237
debc93f8 238 return (
239 @return,
240 'modify return values'
241 );
b751d33f 242};</code></pre>
243</div>
244
245<div class="slide">
246 <h1>Type Constraints</h1>
247
248 <ul>
249 <li>NOT A FULL-BLOWN TYPE SYSTEM!</li>
250 <li>But still darn useful</li>
251 <li>Constrain attribute values</li>
252 <li>Coerce from other types</li>
253 </ul>
254</div>
255
256<div class="slide">
257 <h1>Type Constraint Example</h1>
258
259<pre><code>package Person;
260use Moose;
261
55906a14 262has weight =&gt; (
263 is =&gt; 'ro',
264 <span class="highlight">isa =&gt; 'Int'</span>,
265);
b751d33f 266
267# kaboom
268Person-&gt;new( weight =&gt; 'fat' );</code></pre>
269</div>
270
271<div class="slide">
272 <h1>Delegation</h1>
273
274 <ul>
275 <li>Attributes can define delegations</li>
276 <li>Lets you hide some implementation details</li>
277 <li>Fewer objects to chase around</li>
278 </ul>
279</div>
280
281<div class="slide">
282 <h1>Delegation</h1>
283
284<pre><code>package Person;
285use Moose;
286
55906a14 287has blog_uri =&gt; (
b751d33f 288 is =&gt; 'rw',
289 isa =&gt; 'URI',
debc93f8 290 <span class="highlight">handles =&gt; { 'blog_host' =&gt; 'host' },</span>
b751d33f 291);
292
debc93f8 293<span class="highlight">$person->blog_host;</span>
55906a14 294# really calls $person->blog_uri->host</code></pre>
b751d33f 295</div>
296
297<div class="slide">
298 <h1>Constructors</h1>
299
300 <ul>
301 <li>Moose creates <code>new()</code> for you</li>
debc93f8 302 <li>Provide an optional <code>BUIDARGS()</code> and <code>BUILD()</code></li>
b751d33f 303 </ul>
304</div>
305
306<div class="slide">
307 <h1>Destructors</h1>
308
309 <ul>
310 <li>Provide an optional <code>DEMOLISH()</code></li>
311 </ul>
312</div>
313
314<div class="slide">
315 <h1>Moose Meta-API</h1>
316
317 <ul>
318 <li>Answers questions like ...
319 <ul>
320 <li>What methods does this class have?</li>
321 <li>What are its parents?</li>
322 <li>What attributes does it have (including inherited attributes)?</li>
323 <li>What roles does it do?</li>
324 <li>Much, much, more</li>
325 </ul>
326 </li>
327 </ul>
328</div>
329
330<div class="slide">
331 <h1>Moose Meta-API</h1>
332
333 <ul>
334 <li>Not just for introspection ...
335 <ul>
336 <li>Add methods, attributes, roles, etc</li>
337 <li>Extend and alter core features</li>
338 </ul>
339 </li>
340 </ul>
341</div>
342
343<div class="slide">
344 <h1>Why Moose?</h1>
345
346 <ul>
811952b2 347 <li>A quick bit of propaganda ...</li>
b751d33f 348 </ul>
349</div>
350
351<div class="slide">
352 <h1>With Moose</h1>
353
354 <pre><code>package Person;
355use Moose;
356
357has last_name =&gt; (
358 is =&gt; 'rw',
359 isa =&gt; 'Str',
360);</code></pre>
361</div>
362
363<div class="slide">
364 <h1>Without Moose</h1>
365
366 <pre class="small"><code>package Person;
367use strict;
368use warnings;
369use Carp 'confess';
370
371sub new {
372 my $class = shift;
373 my %args = @_;
374 my $self = {};
375
376 if (exists $args{last_name}) {
377 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
378 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
379 if ref($args{last_name});
380 $self-&gt;{last_nane} = $args{last_name};
381 }
382
383 return bless $self, $class;
384}
385
386sub last_name {
387 my $self = shift;
388
389 if (@_) {
390 my $value = shift;
391 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
392 . &quot;Validation failed for 'Str' with value $value&quot;
393 if ref($value);
394 $self-&gt;{last_name} = $value;
395 }
396
397 return $self-&gt;{last_name};
398}</code></pre>
399
400</div>
401
402<div class="slide">
403 <h1>Side by side</h1>
404
405 <table class="side-by-side">
406 <tr>
407 <td>
408 <pre><code>package Person;
409use Moose;
410
411has last_name =&gt; (
412 is =&gt; 'rw',
413 isa =&gt; 'Str',
414);</code></pre>
415 </td>
416 <td>
417 <pre class="small"><code>package Person;
418use strict;
419use warnings;
420use Carp 'confess';
421
422sub new {
423 my $class = shift;
424 my %args = @_;
425 my $self = {};
426
427 if (exists $args{last_name}) {
428 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
429 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
430 if ref($args{last_name});
431 $self-&gt;{last_nane} = $args{last_name};
432 }
433
434 return bless $self, $class;
435}
436
437sub last_name {
438 my $self = shift;
439
440 if (@_) {
441 my $value = shift;
442 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
443 . &quot;Validation failed for 'Str' with value $value&quot;
444 if ref($value);
445 $self-&gt;{last_name} = $value;
446 }
447
448 return $self-&gt;{last_name};
449}</code></pre>
450 </td>
451 </tr>
452 </table>
453
454</div>
455
456<div class="slide">
457 <h1>Side by side</h1>
458
459 <table class="side-by-side">
460 <tr>
461 <td>
462 <pre><code><span class="match-moose">package Person;</span>
463use Moose;
464
465has last_name =&gt; (
466 is =&gt; 'rw',
467 isa =&gt; 'Str',
468);</code></pre>
469 </td>
470 <td>
471 <pre class="small"><code><span class="match-unsweet">package Person;</span>
472use strict;
473use warnings;
474use Carp 'confess';
475
476sub new {
477 my $class = shift;
478 my %args = @_;
479 my $self = {};
480
481 if (exists $args{last_name}) {
482 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
483 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
484 if ref($args{last_name});
485 $self-&gt;{last_nane} = $args{last_name};
486 }
487
488 return bless $self, $class;
489}
490
491sub last_name {
492 my $self = shift;
493
494 if (@_) {
495 my $value = shift;
496 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
497 . &quot;Validation failed for 'Str' with value $value&quot;
498 if ref($value);
499 $self-&gt;{last_name} = $value;
500 }
501
502 return $self-&gt;{last_name};
503}</code></pre>
504 </td>
505 </tr>
506 </table>
507</div>
508
509<div class="slide">
510 <h1>Side by side</h1>
511
512 <table class="side-by-side">
513 <tr>
514 <td>
515 <pre><code>package Person;
516<span class="match-moose">use Moose;</span>
517
518has last_name =&gt; (
519 is =&gt; 'rw',
520 isa =&gt; 'Str',
521);</code></pre>
522 </td>
523 <td>
524 <pre class="small"><code>package Person;
525<span class="match-unsweet">use strict;
526use warnings;
527use Carp 'confess';
528
529sub new {
530 my $class = shift;
531 my %args = @_;
532 my $self = {};</span>
533
534 if (exists $args{last_name}) {
535 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
536 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
537 if ref($args{last_name});
538 $self-&gt;{last_nane} = $args{last_name};
539 }
540
541 <span class="match-unsweet">return bless $self, $class;
542}</span>
543
544sub last_name {
545 my $self = shift;
546
547 if (@_) {
548 my $value = shift;
549 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
550 . &quot;Validation failed for 'Str' with value $value&quot;
551 if ref($value);
552 $self-&gt;{last_name} = $value;
553 }
554
555 return $self-&gt;{last_name};
556}</code></pre>
557 </td>
558 </tr>
559 </table>
560</div>
561
562<div class="slide">
563 <h1>Side by side</h1>
564
565 <table class="side-by-side">
566 <tr>
567 <td>
568 <pre><code>package Person;
569use Moose;
570
571<span class="match-moose">has last_name =&gt; (</span>
572 is =&gt; 'rw',
573 isa =&gt; 'Str',
574<span class="match-moose">);</span></code></pre>
575 </td>
576 <td>
577 <pre class="small"><code>package Person;
578use strict;
579use warnings;
580use Carp 'confess';
581
582sub new {
583 my $class = shift;
584 my %args = @_;
585 my $self = {};
586
587 <span class="match-unsweet">if (exists $args{last_name}) {</span>
588 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
589 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
590 if ref($args{last_name});
591 <span class="match-unsweet">$self-&gt;{last_nane} = $args{last_name};
592 }</span>
593
594 return bless $self, $class;
595}
596
597sub last_name {
598 my $self = shift;
599
600 if (@_) {
601 my $value = shift;
602 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
603 . &quot;Validation failed for 'Str' with value $value&quot;
604 if ref($value);
605 $self-&gt;{last_name} = $value;
606 }
607
608 return $self-&gt;{last_name};
609}</code></pre>
610 </td>
611 </tr>
612 </table>
613</div>
614
615<div class="slide">
616 <h1>Side by side</h1>
617
618 <table class="side-by-side">
619 <tr>
620 <td>
621 <pre><code>package Person;
622use Moose;
623
624has last_name =&gt; (
625 <span class="match-moose">is =&gt; 'rw',</span>
626 isa =&gt; 'Str',
627);</code></pre>
628 </td>
629 <td>
630 <pre class="small"><code>package Person;
631use strict;
632use warnings;
633use Carp 'confess';
634
635sub new {
636 my $class = shift;
637 my %args = @_;
638 my $self = {};
639
640 if (exists $args{last_name}) {
641 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
642 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
643 if ref($args{last_name});
644 $self-&gt;{last_nane} = $args{last_name};
645 }
646
647 return bless $self, $class;
648}
649
650<span class="match-unsweet">sub last_name {
651 my $self = shift;
652
653 if (@_) {
654 my $value = shift;</span>
655 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
656 . &quot;Validation failed for 'Str' with value $value&quot;
657 if ref($value);
658 <span class="match-unsweet">$self-&gt;{last_name} = $value;
659 }
660
661 return $self-&gt;{last_name};
662}</span></code></pre>
663 </td>
664 </tr>
665 </table>
666</div>
667
668<div class="slide">
669 <h1>Side by side</h1>
670
671 <table class="side-by-side">
672 <tr>
673 <td>
674 <pre><code>package Person;
675use Moose;
676
677has last_name =&gt; (
678 is =&gt; 'rw',
679 <span class="match-moose">isa =&gt; 'Str',</span>
680);</code></pre>
681 </td>
682 <td>
683 <pre class="small"><code>package Person;
684use strict;
685use warnings;
686use Carp 'confess';
687
688sub new {
689 my $class = shift;
690 my %args = @_;
691 my $self = {};
692
693 if (exists $args{last_name}) {
694 <span class="match-unsweet">confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
695 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
696 if ref($args{last_name});</span>
697 $self-&gt;{last_nane} = $args{last_name};
698 }
699
700 return bless $self, $class;
701}
702
703sub last_name {
704 my $self = shift;
705
706 if (@_) {
707 my $value = shift;
708 <span class="match-unsweet">confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
709 . &quot;Validation failed for 'Str' with value $value&quot;
710 if ref($value);</span>
711 $self-&gt;{last_name} = $value;
712 }
713
714 return $self-&gt;{last_name};
715}</code></pre>
716 </td>
717 </tr>
718 </table>
719</div>
720
721<div class="slide">
722 <h1>Side by side</h1>
723
724 <table class="side-by-side">
725 <tr class="incremental">
726 <td>5 lines</td>
727 <td>21 lines</td>
728 </tr>
729 <tr class="incremental">
730 <td>92 characters</td>
731 <td>741 characters</td>
732 </tr>
733 <tr>
734 <td>
735 <pre><code>package Person;
736use Moose;
737
738has last_name =&gt; (
739 is =&gt; 'rw',
740 isa =&gt; 'Str',
741);</code></pre>
742 </td>
743 <td>
744 <pre class="small"><code>package Person;
745use strict;
746use warnings;
747use Carp 'confess';
748
749sub new {
750 my $class = shift;
751 my %args = @_;
752 my $self = {};
753
754 if (exists $args{last_name}) {
755 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
756 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
757 if ref($args{last_name});
758 $self-&gt;{last_nane} = $args{last_name};
759 }
760
761 return bless $self, $class;
762}
763
764sub last_name {
765 my $self = shift;
766
767 if (@_) {
768 my $value = shift;
769 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
770 . &quot;Validation failed for 'Str' with value $value&quot;
771 if ref($value);
772 $self-&gt;{last_name} = $value;
773 }
774
775 return $self-&gt;{last_name};
776}</code></pre>
777 </td>
778 </tr>
779 </table>
780</div>
781
782<div class="slide">
783 <h1>Typo?</h1>
784
785 <pre class="small"><code>sub new {
786 my $class = shift;
787 my %args = @_;
788 my $self = {};
789
790 if (exists $args{last_name}) {
791 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
792 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
793 if ref($args{last_name});
794 $self-&gt;{last_nane} = $args{last_name};
795 }
796
797 return bless $self, $class;
798}</code></pre>
799</div>
800
801<div class="slide">
802 <h1>Typo?</h1>
803
804 <pre class="small"><code>if (exists $args{last_name}) {
805 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
806 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
807 if ref($args{last_name});
808 $self-&gt;{last_nane} = $args{last_name};
809}</code></pre>
810</div>
811
812<div class="slide">
813 <h1>Typo?</h1>
814
815 <code>$self-&gt;{last_nane} = $args{last_name};</code>
816</div>
817
818<div class="slide">
819 <h1>Typo?</h1>
8d1ce1d7 820 <code>$self-&gt;{last_na<span class="wrong">n</span>e}</code>
b751d33f 821</div>
822
823<div class="slide">
824 <h1>Why Moose?</h1>
825
826 <pre><code>package Person;
827use Moose;
828
829has last_name =&gt; (
830 is =&gt; 'rw',
831 isa =&gt; 'Str',
832);</code></pre>
833</div>
834
835<div class="slide fake-slide0">
ba1c9923 836 <h1>Part 1: Moose Classes</h1>
b751d33f 837</div>
838
839<div class="slide">
840 <h1>Moose Classes</h1>
841
842 <ul>
843 <li>Moose classes are Perl packages which <code>use Moose</code></li>
844 </ul>
845</div>
846
847<div class="slide">
848 <h1>Moose.pm and Your Class</h1>
849
850 <pre><code>package Person;
851use Moose;</code></pre>
852
853 <ul>
854 <li><code>Moose.pm</code> provides declarative sugar</li>
9b195048 855 <li>Turns on <code>strict</code> and <code>warnings</code></li>
b751d33f 856 <li>Creates metaclasses for your class: <code>Person-&gt;meta</code></li>
857 <li>Moose classes automatically inherit from <code>Moose::Object</code></li>
858 </ul>
859</div>
860
861<div class="slide">
862 <h1>What <code>Moose::Object</code> Provides</h1>
863
864 <ul>
865 <li>Constructor - <code>new()</code></li>
866 <li>Calls your <code>BUILDARGS()</code> and/or <code>BUILD()</code></li>
867 <li>Calls your <code>DEMOLISH</code> during object destruction</li>
868 </ul>
869</div>
870
871<div class="slide">
d6c8786d 872 <h1>BUILDARGS</h1>
873
874 <ul>
875 <li>Takes <code>@_</code>, returns a hash reference of attribute names/value</li>
876 <li>Accepts a hash or hashref; throws otherwise</li>
877 <li>Provide your own for other cases</li>
878 <li><strong>Always</strong> call <code>$class-&gt;SUPER::BUILDARGS(@_)</code> as a fallback!</li>
879 </ul>
880</div>
881
882<div class="slide">
883 <h1>BUILDARGS Example</h1>
884
885 <pre><code>package Person;
886use Moose;
887
888sub BUILDARGS {
889 my $class = shift;
890
5e2eb691 891 if ( @_ == 1 &amp;&amp; ! ref $_[0] ) {
d6c8786d 892 <span class="highlight">return { ssn =&gt; $_[0] };</span>
893 }
d6c8786d 894 <span class="highlight">return $class-&gt;SUPER::BUILDARGS(@_)</span>;
895}
896
897<span class="highlight">Person-&gt;new('123-45-6789')</span></code></pre>
898</div>
899
900<div class="slide">
901 <h1>BUILD</h1>
902
903 <ul>
904 <li>Called after object is created, before <code>new</code> returns</li>
905 <li>Chance to do more complex validation, set complex attributes</li>
906 <li>Called in reverse inheritance order, parents to children</li>
907 <li>Return value is ignored</li>
908 </ul>
909</div>
910
911<div class="slide">
912 <h1>BUILD Example</h1>
913
914 <pre><code>package Person;
915use Moose;
916
917sub BUILD {
918 my $self = shift;
919
920 if ( $self-&gt;country_of_residence
921 eq 'USA' ) {
922 die 'All US residents'
923 . ' must have an SSN'
924 unless $self-&gt;has_ssn;
925 }
926}</code></pre>
927</div>
928
929<div class="slide">
7205c6ef 930 <h1>Object Construction a la Moose</h1>
931
932 <pre><code>Person-&gt;new(@_)</code></pre>
933
934 <ol>
935 <li>Calls <code>Person-&gt;BUILDARGS(@_)</code> to turn <code>@_</code> into a hashref</li>
936 <li>Blesses a reference</li>
937 <li>Populates attributes based on the hashref from #1</li>
938 <li>Calls <code>$new_object->BUILDALL($constructor_args)</code>
939 <br />... which calls all <code>BUILD</code> methods</li>
940 <li>Returns the object</li>
941 </ol>
942</div>
943
944<div class="slide">
17d7a564 945 <h1>The Object is Opaque</h1>
7205c6ef 946
947 <ul>
948 <li>Technically it's a hash reference</li>
949 <li><span class="wrong">If you <em>ever</em> treat it as one <strong>you are doing it wrong!</strong></span></li>
950 </ul>
951</div>
952
953<div class="slide">
d6c8786d 954 <h1>DEMOLISH</h1>
955
956 <ul>
957 <li>Like <code>DESTROY</code>, but Moose makes sure all <code>DEMOLISH</code> methods in a hierarchy are called</li>
958 <li>Called in normal inheritance order, children to parents</li>
959 </ul>
960</div>
961
962<div class="slide">
b751d33f 963 <h1>extends</h1>
964
965 <ul>
966 <li><code>extends</code> is sugar for declaring parent classes</li>
967 </ul>
968
969 <pre><code>package Employee;
970use Moose;
971<span class="highlight">extends 'Person';</span></code></pre>
972</div>
973
974<div class="slide">
975 <h1>extends</h1>
976
977 <ul>
978 <li>Each call to <code>extends</code> <strong>resets</strong> your parents</li>
979 </ul>
980
5d572684 981 <h2 class="wrong">Wrong</h2>
b751d33f 982
9b195048 983 <pre><code>package EvilEmployee;
b751d33f 984use Moose;
985extends 'Person';
55906a14 986extends 'Thief';</code></pre>
b751d33f 987
5d572684 988 <h2 class="right">Right</h2>
b751d33f 989
9b195048 990 <pre><code>package EvilEmployee;
b751d33f 991use Moose;
55906a14 992extends 'Person', 'Thief';</code></pre>
b751d33f 993</div>
994
995<div class="slide">
996 <h1>Extending un-Moose-y Parents</h1>
997
998 <pre><code>package My::LWP;
999use Moose;
55906a14 1000extends 'LWP';</code></pre>
b751d33f 1001
1002 <ul>
1003 <li>No <code>Moose::Object</code>, so ...
1004 <ul>
1005 <li>No attribute-handling <code>new()</code></li>
1006 <li>No <code>BUILDARGS()</code> or <code>BUILD()</code></li>
1007 <li>No <code>DEMOLISH()</code></li>
1008 </ul>
1009 </li>
1010 <li>But see <code>MooseX::NonMoose</code> for a workaround</li>
1011 </ul>
1012</div>
1013
1014<div class="slide">
9fa24ee2 1015 <h1><code>override</code> and <code>super</code></h1>
9b195048 1016
1017 <ul>
9fa24ee2 1018 <li><code>override</code> is another method modifier</li>
9b195048 1019 <li>An alternative to Perl's <code>SUPER::</code></li>
1020 </ul>
1021</div>
1022
1023<div class="slide">
9fa24ee2 1024 <h1><code>override</code> and <code>super</code></h1>
9b195048 1025
1026 <pre><code>package Employee;
1027use Moose;
1028
26164c8d 1029<span class="current incremental">extends 'Person';</span>
9b195048 1030
9fa24ee2 1031<span class="incremental">override</span> work =&gt; sub {
9b195048 1032 my $self = shift;
1033
debc93f8 1034 die "Pay me first"
1035 unless $self-&gt;got_paid;
9b195048 1036 <span class="incremental">super();</span>
1037}<span class="incremental">;</span></code></pre>
55906a14 1038</div>
9b195048 1039
1040<div class="slide">
1041 <h1>Caveat <code>super</code></h1>
1042
1043 <ul>
1044 <li>Mostly like <code>$self-&gt;SUPER::work(@_)</code></li>
1045 <li><strong>But</strong> cannot change <code>@_</code>!</li>
1046 <li>Binds the parent's method at compile time</li>
1047 </ul>
1048</div>
1049
1050<div class="slide">
e43c4c2a 1051 <h1>Minimal Attributes</h1>
9b195048 1052
1053 <ul>
1054 <li><code>has 'foo'</code></li>
1055 <li>Use <code>is =&gt; 'ro'</code> or <code>is =&gt; 'rw'</code></li>
1056 <li>Attributes without "is" have no accessors</li>
1057 </ul>
1058</div>
1059
1060<div class="slide">
1061 <h1>Read-write attributes</h1>
1062
1063 <pre><code>package Person;
1064use Moose;
1065
55906a14 1066has first_name =&gt; ( <span class="highlight">is =&gt; 'rw'</span> );
9b195048 1067
1068my $person =
1069 Person-&gt;new( first_name =&gt; 'Dave' );
1070
1071$person-&gt;first_name('Stevan');
1072print $person-&gt;first_name; # Stevan</code></pre>
1073
1074</div>
1075
1076<div class="slide">
1077 <h1>Read-only attributes</h1>
1078
1079 <pre><code>package Person;
1080use Moose;
1081
55906a14 1082has first_name =&gt; ( <span class="highlight">is =&gt; 'ro'</span> );
9b195048 1083
1084my $person =
1085 Person-&gt;new( first_name =&gt; 'Dave' );
1086
1087$person-&gt;first_name('Stevan');
1088print $person-&gt;first_name; # Dave</code></pre>
1089
1090</div>
1091
1092<div class="slide">
1093 <h1>There is More to Come</h1>
1094
1095 <ul>
1096 <li>Attributes have a <em>lot</em> of features</li>
1097 </ul>
1098</div>
1099
1100<div class="slide">
b751d33f 1101 <h1>Cleaning Up Moose Droppings</h1>
1102
1103 <pre><code>package Person;
1104use Moose;
1105
1106# true
1107Person->can('extends');</code></pre>
1108
1109 <ul>
1110 <li>Not very hygienic</li>
1111 </ul>
1112</div>
1113
1114<div class="slide">
1115 <h1>Cleaning Up Moose Droppings</h1>
1116
1117 <pre><code>package Person;
1118use Moose;
1119
1120...
1121
1122no Moose;
1123
1124# false
1125Person->can('extends');</code></pre>
1126</div>
1127
1128<div class="slide">
1129 <h1>No Moose</h1>
1130
1131 <ul>
1132 <li><code>no Moose</code> at the end of a package is a best practice</li>
debc93f8 1133 <li>Or <code>use namespace::autoclean</code> at the top</li>
b751d33f 1134 <li>Just do it</li>
1135 </ul>
1136</div>
1137
1138<div class="slide">
1139 <h1>Immutability</h1>
1140
1141 <ul>
1142 <li><span style="font-family: URW Chancery L; font-size: 140%">Stevan's Incantation of Fleet-Footedness</span></li>
1143 </ul>
1144
1145 <pre><code>package Person;
1146use Moose;
1147
1148<span class="highlight">__PACKAGE__->meta->make_immutable;</span></code></pre>
1149</div>
1150
9b195048 1151<div class="slide">
1152 <h1>What <code>make_immutable</code> does</h1>
1153
1154 <ul>
1155 <li>Magic</li>
1156 <li>Uses <code>eval</code> to "inline" a constructor</li>
1157 <li>Memoizes a lot of meta-information</li>
1158 <li>Makes loading your class slower</li>
1159 <li>Makes object creation <em>much</em> faster</li>
1160 </ul>
1161</div>
1162
1163<div class="slide">
1164 <h1>When to Immutabilize?</h1>
1165
1166 <ul>
1167 <li><em>Almost</em> always</li>
1168 <li>Startup time vs execution time</li>
1169 </ul>
1170</div>
1171
ddd87d75 1172<div class="slide">
55906a14 1173 <h1>Classes Summary</h1>
1174
1175 <ul>
1176 <li><code>use Moose</code></li>
1177 <li><code>Class-&gt;meta</code></li>
1178 <li><code>Moose::Object</code> base class</li>
9fa24ee2 1179 <li><code>extends</code>, <code>override</code>, and <code>super</code></li>
55906a14 1180 <li>Simple attributes: <code>has</code>, <code>is&nbsp;=&gt;&nbsp;'ro'</code>, &amp; <code>is&nbsp;=&gt;&nbsp;'rw'</code></li>
1181 <li><code>no Moose</code></li>
1182 <li><code>__PACKAGE__-&gt;meta-&gt;make_immutable</code></li>
1183 </ul>
1184</div>
1185
1186<div class="slide">
26164c8d 1187 <h1>Questions?</h1>
1188</div>
1189
1190<div class="slide">
ba1c9923 1191 <h1>Exercises</h1>
ddd87d75 1192
8d1ce1d7 1193 <pre># cd exercises
bcbafd14 1194
4a2daaa5 1195# perl bin/prove -lv t/00-prereq.t
ddd87d75 1196
bcbafd14 1197# perl install-moose (if needed)
ddd87d75 1198
ba1c9923 1199# perl bin/prove -lv t/01-classes.t
1200
55906a14 1201Iterate til this passes all its tests</pre>
1202</div>
1203
1204<div class="slide fake-slide0">
1205 <h1>Part 2: Roles</h1>
1206</div>
1207
1208<div class="slide">
1209 <h1>Just What Is a Role?</h1>
1210
1211 <ul>
1212 <li>Mixin? Interface? Trait?</li>
1213 <li>Yes ... and more!</li>
1214 </ul>
1215</div>
1216
1217<div class="slide">
debc93f8 1218 <h1>Roles - State <strong>and</strong> Behavior</h1>
55906a14 1219
1220 <pre><code>package HasPermissions;
1221use Moose::Role;
26164c8d 1222<span class="current incremental"># state
55906a14 1223has access_level =&gt; ( is =&gt; 'rw' );</span>
1224
1225<span class="incremental"># behavior
1226sub can_access {
1227 my $self = shift;
1228 my $required = shift;
1229
debc93f8 1230 return $self-&gt;access_level
1231 &gt;= $required;
55906a14 1232}</span></code></pre>
1233
1234</div>
1235
1236<div class="slide">
1237 <h1>Roles Can Define Interfaces</h1>
1238
1239 <pre><code>package Printable;
1240use Moose::Role;
1241
1242requires 'as_string';</code></pre>
1243</div>
1244
1245<div class="slide">
1246 <h1>Roles Can Do All Three</h1>
1247
1248 <pre><code>package Printable;
1249use Moose::Role;
1250
1251requires 'as_string';
1252
1253has has_been_printed =&gt; ( is =&gt; 'rw' );
1254
1255sub print {
1256 my $self = shift;
1257 print $self-&gt;as_string;
1258 $self-&gt;has_been_printed(1);
1259}</code></pre>
1260</div>
1261
1262<div class="slide">
1263 <h1>Classes Consume Roles</h1>
1264
1265 <pre><code>package Person;
1266use Moose;
1267
1268with 'HasPermissions';</code></pre>
1269</div>
1270
1271<div class="slide">
1272 <h1>Classes Consume Roles</h1>
1273
1274<pre><code>my $person = Person-&gt;new(
debc93f8 1275 first_name =&gt; 'Kenichi',
1276 last_name =&gt; 'Asai',
55906a14 1277 access_level =&gt; 42,
1278);
1279
1280print $person-&gt;full_name
1281 . ' has '
1282 . $person-&gt;can_access(42)
1283 ? 'great power'
1284 : 'little power';</code></pre>
1285</div>
1286
1287<div class="slide">
1288 <h1>Roles in Practice</h1>
1289
1290 <ul>
1291 <li>Consuming a role =~ inlining the role</li>
1292 </ul>
1293</div>
1294
1295<div class="slide">
1296 <h1>In Other Words ...</h1>
1297
1298<pre><code>package Person;
1299use Moose;
1300
1301<span class="highlight">with 'Printable';</span></code></pre>
1302</div>
1303
1304<div class="slide">
1305 <h1>In Other Words ...</h1>
1306
1307<pre><code>package Person;
1308use Moose;
1309
1310<span class="delete">with 'Printable';</span>
1311
1312<span class="highlight">has has_been_printed =&gt; ( is =&gt; 'rw' );
1313
1314sub print {
1315 my $self = shift;
1316 print $self-&gt;as_string;
1317 $self-&gt;has_been_printed(1);
1318}</span></code></pre>
1319</div>
1320
1321<div class="slide">
1322 <h1>Except</h1>
1323
1324 <ul>
1325 <li>Role consumption is introspectable</li>
1326 </ul>
1327
1328 <pre><code>if ( Person-&gt;does('Printable') ) { ... }
1329
1330# or ...
1331
debc93f8 1332Person-&gt;meta-&gt;does('Printable')</code></pre>
55906a14 1333
1334</div>
1335
1336<div class="slide">
1337 <h1>These Names Are the Same</h1>
1338
1339 <ul>
1340 <li>What if a role and class define the same method?</li>
1341 <li>A class's <em>local</em> methods win over the role's</li>
1342 <li>The role's methods win over the class's <em>inherited</em> methods</li>
1343 </ul>
1344</div>
1345
1346<div class="slide">
1347 <h1>Conflicts Between Roles</h1>
1348
1349 <ul>
1350 <li>Two roles with a method of the same name</li>
1351 <li>Generates a compile-time error when consumed by a class</li>
1352 </ul>
1353</div>
1354
1355<div class="slide">
1356 <h1>Conflict Example</h1>
1357
1358 <pre><code>package IsFragile;
1359use Moose::Role;
1360
1361sub break { ... }
1362
1363package CanBreakdance;
1364use Moose::Role;
1365
1366sub break { ... }</code></pre>
1367</div>
1368
1369<div class="slide">
1370 <h1>Conflict Example</h1>
1371
1372 <pre><code>package FragileDancer;
1373use Moose;
1374
1375<span class="highlight">with 'IsFragile', 'CanBreakdance';</span></code></pre>
1376
1377 <ul>
1378 <li>Only one <code>with</code>!</li>
1379 </ul>
1380</div>
1381
1382<div class="slide">
1383 <h1>Conflict Resolution</h1>
1384
1385 <ul>
0412f089 1386 <li>The consuming class must resolve the conflict by implementing the method</li>
55906a14 1387 <li>Can use some combination of method exclusion and aliasing</li>
1388 </ul>
1389</div>
1390
1391<div class="slide">
1392 <h1>Method Aliasing</h1>
1393
1394 <pre><code>package FragileDancer;
1395use Moose;
1396
1397<span class="highlight">with 'IsFragile' =>
debc93f8 1398 { -alias =>
55906a14 1399 { break => 'break_bone' } },
1400 'CanBreakdance' =>
debc93f8 1401 { -alias =>
55906a14 1402 { break => 'break_it_down' } };</span></code></pre>
1403
1404 <ul>
1405 <li>Renames the roles' methods</li>
1406 <li>Still conflicts, need to <code>exclude</code> as well</li>
1407 </ul>
1408</div>
1409
1410<div class="slide">
1411 <h1>Method Exclusion</h1>
1412
1413 <pre><code>package FragileDancer;
1414use Moose;
1415
1416<span class="highlight">with 'IsFragile' =>
debc93f8 1417 { -alias =>
55906a14 1418 { break => 'break_bone' },
debc93f8 1419 -excludes => 'break' },
55906a14 1420 'CanBreakdance' =>
debc93f8 1421 { -alias =>
55906a14 1422 { break => 'break_dance' },
debc93f8 1423 -excludes => 'break' };</span></code></pre>
55906a14 1424</div>
1425
1426<div class="slide">
1427 <h1>And then ...</h1>
1428
1429 <pre><code>package FragileDancer;
1430use Moose;
ddd87d75 1431
55906a14 1432sub break {
1433 my $self = shift;
1434
1435 $self->break_dance;
232c184d 1436 if ( rand(1) &lt; 0.5 ) {
55906a14 1437 $self->break_bone;
1438 }
1439}</code></pre>
1440</div>
1441
1442<div class="slide">
1443 <h1>Still Full of Fail</h1>
1444
1445 <ul>
1446 <li>Roles are also about semantics!</li>
1447 <li>We've fulfilled the letter and lost the spirit</li>
1448 <li>Roles have a <em>meaning</em></li>
1449 <li>Think twice before blindly aliasing and excluding methods!</li>
1450 </ul>
1451</div>
1452
1453<div class="slide">
1454 <h1>Hot Role-on-Role Action</h1>
1455
1456 <pre><code>package Comparable;
1457use Moose::Role;
1458
1459requires 'compare';</code></pre>
1460</div>
1461
1462<div class="slide">
1463 <h1>Hot Role-on-Role Action</h1>
1464
1465 <pre><code>package TestsEquality;
1466use Moose::Role;
1467
1468with 'Comparable';
1469
1470sub is_equal {
1471 my $self = shift;
1472 return $self->compare(@_) == 0;
1473}</code></pre>
1474</div>
1475
1476<div class="slide">
1477 <h1>And then ...</h1>
1478
1479 <pre><code>package Integer;
1480use Moose;
1481
1482with 'TestsEquality';
1483
1484# Satisfies the Comparable role
1485sub compare { ... }
1486
1487Integer->does('TestsEquality'); # true
1488Integer->does('Comparable'); # also true!</code></pre>
1489</div>
1490
1491<div class="slide">
1492 <h1>Name Conflicts Between Roles</h1>
1493
1494 <pre><code>package HasSubProcess;
1495use Moose::Role;
1496
1497<span class="highlight">sub execute { ... }</span>
1498
1499package Killer;
1500use Moose::Role;
1501
1502with 'HasSubProcess';
1503
1504<span class="highlight">sub execute { ... }</span></code></pre>
1505</div>
1506
1507<div class="slide">
1508 <h1>Delayed Conflict</h1>
1509
1510 <pre><code>package StateOfTexas;
1511with 'Killer';</code></pre>
1512
1513 <ul>
1514 <li><code>StateOfTexas</code> must implement its own <code>execute</code></li>
1515 <li>But loading the <code>Killer</code> role by itself does not cause an error</li>
1516 </ul>
1517</div>
1518
1519<div class="slide">
1520 <h1>Roles as Interfaces</h1>
1521
1522 <ul>
1523 <li>Roles can <code>require</code> methods of their consumers</li>
1524 <li>Compile-time checks</li>
1525 <li>Method must exist when the role is consumed</li>
1526 </ul>
1527</div>
1528
1529<div class="slide">
1530 <h1>The Attribute Gotcha</h1>
1531
1532<pre><code>package HasSize;
1533use Moose::Role;
1534
26164c8d 1535<span class="current incremental">requires 'size';</span>
55906a14 1536
1537package Shirt;
1538use Moose;
1539
1540<span class="incremental">with 'HasSize';
1541
1542has size => ( is => 'ro' );</span></code></pre>
1543</div>
1544
1545<div class="slide">
1546 <h1>The Attribute Gotcha Workaround</h1>
1547
1548 <pre><code>package HasSize;
1549use Moose::Role;
1550
1551requires 'size';
1552
1553package Shirt;
1554use Moose;
1555
1556has size => ( is => 'ro' );
1557
1558with 'HasSize';</code></pre>
1559</div>
1560
1561<div class="slide">
1562 <h1>Compile-time Is a Lie</h1>
1563
1564 <ul>
1565 <li>Really, it's <em>package load</em> time</li>
1566 <li>That's run-time, but before the "real" run-time</li>
1567 <li>Moose does not rewire Perl, it's just sugar!</li>
1568 <li>(but <code>MooseX::Declare</code> <em>does</em> rewire Perl)</li>
1569 </ul>
1570</div>
1571
1572<div class="slide">
1573 <h1>Enforcing Roles</h1>
1574
1575 <pre><code>package Comparison;
1576use Moose;
1577
1578has [ 'left', 'right' ] => (
1579 is => 'ro',
1580 <span class="highlight">does => 'Comparable',</span>
1581);
1582</code></pre>
1583
1584 <ul>
1585 <li>A sneak peek at type constraints</li>
1586 </ul>
1587</div>
1588
1589
1590<div class="slide">
1591 <h1>Roles Can Be Applied to Objects</h1>
1592
1593 <pre><code>use Moose::Util qw( apply_all_roles );
1594
1595my $fragile_person = Person->new( ... );
debc93f8 1596apply_all_roles( $fragile_person,
1597 'IsFragile' );</code></pre>
55906a14 1598
1599 <ul>
1600 <li>Does not change the <code>Person</code> class</li>
1601 <li>Works with non-Moose classes, great for monkey-patching!</li>
1602 </ul>
1603</div>
1604
1605<div class="slide">
1606 <h1>Roles Are Dirty Too</h1>
1607
1608 <ul>
1609 <li>Once again, clean up those Moose droppings</li>
1610 </ul>
1611
1612 <pre><code>package Comparable;
1613use Moose::Role;
1614
1615requires 'compare';
1616
1617<span class="highlight">no Moose::Role;</span></code></pre>
1618
1619 <ul>
1620 <li>But roles cannot be made immutable</li>
1621 </ul>
1622</div>
1623
1624<div class="slide">
1625 <h1>The Zen of Roles</h1>
1626
1627 <ul>
1628 <li>Roles represent discrete units of ...
1629 <ul>
1630 <li>state</li>
1631 <li>behavior</li>
1632 <li>interface</li>
1633 </ul>
1634 </li>
1635 <li>Roles are shareable between unrelated classes</li>
1636 <li>Roles are what a class <em>does</em>, not what it <em>is</em></li>
1637 <li>Roles <em>add</em> functionality, inheritance <em>specializes</em></li>
1638 </ul>
1639</div>
1640
1641<div class="slide">
1642 <h1>Abstract Examples</h1>
1643
1644 <ul>
1645 <li>Human <em>@ISA</em> Animal</li>
1646 <li>Human <em>does</em> Toolmaker (as <em>does</em> Chimpanzee)</li>
1647 <li>Car <em>@ISA</em> Vehicle</li>
1648 <li>Car <em>does</em> HasEngine</li>
1649 </ul>
1650</div>
1651
1652<div class="slide">
1653 <h1>Real Examples</h1>
1654
1655 <ul>
1656 <li>Objects representing SQL database components and queries
1657 <ul>
1658 <li>Schema, Table, Column, ColumnAlias</li>
1659 <li>Select, Insert, Update, Delete</li>
1660 </ul>
1661 </li>
1662 </ul>
1663</div>
1664
1665<div class="slide">
1666 <h1>Real Examples</h1>
1667
1668 <ul>
1669 <li>Column and ColumnAlias both <em>do</em> ColumnLike</li>
1670 <li>ColumnLike things can be used in certain parts of queries</li>
1671 <li>All queries <em>do</em> HasWhereClause</li>
1672 <li>Select <em>does</em> Comparable and Selectable (for subselects)</li>
1673 <li>A where clause requires its components to <em>do</em> Comparable</li>
1674 </ul>
1675</div>
1676
1677<div class="slide">
26164c8d 1678 <h1>Roles Summary</h1>
1679
1680 <ul>
1681 <li>Roles can define an interface with <code>requires</code></li>
1682 <li>Roles can have state (attributes) and behavior (methods)</li>
1683 <li>Roles can mix interface, state, &amp; behavior</li>
1684 <li>Roles are composed (flattened) into classes</li>
1685 <li>Roles can do other roles</li>
1686 <li>Roles can be used as a type in APIs (must do Comparable)</li>
1687 </ul>
1688</div>
1689
1690<div class="slide">
1691 <h1>Questions?</h1>
1692</div>
1693
1694<div class="slide">
55906a14 1695 <h1>Exercises</h1>
1696
8d1ce1d7 1697 <pre># cd exercises
55906a14 1698# perl bin/prove -lv t/02-roles.t
1699
1700Iterate til this passes all its tests</pre>
1701</div>
1702
8d1ce1d7 1703<div class="slide fake-slide0">
1704 <h1>Part 3: Basic Attributes</h1>
1705</div>
1706
1707<div class="slide">
1708 <h1>Attributes Are Huge</h1>
1709
1710 <ul>
1711 <li>Moose's biggest feature</li>
1712 <li>The target of <em>many</em> MooseX modules</li>
1713 </ul>
1714</div>
1715
1716<div class="slide">
1717 <h1>Quick Review</h1>
1718
1719 <ul>
1720 <li>Declared with <code>has</code></li>
1721 <li>Read-only or read-write</li>
1722 </ul>
1723
1724 <pre><code>package Shirt;
1725use Moose;
1726
1727has 'color' =&gt; ( is =&gt; 'ro' );
1728has 'is_ripped' =&gt; ( is =&gt; 'rw' );</code></pre>
1729</div>
1730
1731<div class="slide">
1732 <h1>Required-ness</h1>
1733
1734 <ul>
1735 <li>Required means "must be passed to the constructor"</li>
1736 <li>But can be <code>undef</code></li>
1737 </ul>
1738</div>
1739
1740<div class="slide">
1741 <h1>Required-ness</h1>
1742
1743 <pre><code>package Person;
1744use Moose;
1745
1746has first_name =&gt; (
1747 is =&gt; 'ro',
26164c8d 1748 <span class="current incremental">required =&gt; 1,</span>
8d1ce1d7 1749);
1750
1751<span class="incremental">Person->new( first_name =&gt; undef ); # ok
1752Person->new(); # kaboom</span></code></pre>
1753</div>
1754
1755<div class="slide">
1756 <h1>Default and Builder</h1>
1757
1758 <ul>
1759 <li>Attributes can have defaults</li>
1760 <li>Simple non-referecne scalars (number, string)</li>
1761 <li>Subroutine reference</li>
1762 <li>A builder method</li>
1763 </ul>
1764</div>
1765
1766<div class="slide">
1767 <h1>Default</h1>
1768
1769 <ul>
1770 <li>Can be a non-reference scalar (including <code>undef</code>)</li>
1771 </ul>
1772
1773 <pre><code>package Person;
1774use Moose;
1775
1776has bank =&gt; (
1777 is =&gt; 'rw',
1778 default =&gt; 'Spire FCU',
1779);</code></pre>
1780</div>
1781
1782<div class="slide">
1783 <h1>Default</h1>
1784
1785 <ul>
1786 <li>Can be a subroutine reference</li>
1787 </ul>
1788
1789 <pre><code>package Person;
1790use Moose;
1791
1792has bank =&gt; (
1793 is =&gt; 'rw',
1794 default =&gt;
1795 sub { Bank-&gt;new(
1796 name =&gt; 'Spire FCU' ) },
1797);</code></pre>
1798</div>
1799
1800<div class="slide">
debc93f8 1801 <h1>Subroutine Reference Default</h1>
8d1ce1d7 1802
1803 <ul>
1804 <li>Called as a method on the object</li>
1805 <li>Called anew for each object</li>
1806 </ul>
1807</div>
1808
1809<div class="slide">
1810 <h1>Why No Other Reference Types?</h1>
1811
1812 <pre><code>package Person;
1813use Moose;
1814
1815has bank =&gt; (
1816 is =&gt; 'rw',
1817 <span class="wrong">default =&gt; Bank-&gt;new(
1818 name =&gt; 'Spire FCU' ),</span>
1819);</code></pre>
1820
1821 <ul>
1822 <li>Now <strong>every</strong> person shares the <strong>same</strong> Bank object!</li>
1823 </ul>
1824</div>
1825
1826<div class="slide">
1827 <h1>Defaulting to an Empty Reference</h1>
1828
1829 <pre><code>package Person;
1830use Moose;
1831
1832has packages =&gt; (
1833 is =&gt; 'rw',
1834 default =&gt; <span class="highlight">sub { [] }</span>,
1835);</code></pre>
1836</div>
1837
1838<div class="slide">
1839 <h1>What if I Want to Share?</h1>
1840
1841 <pre><code>package Person;
1842use Moose;
1843
1844my $highlander_bank =
1845 Bank-&gt;new( name =&gt; 'Spire FCU' );
1846
1847has bank =&gt; (
1848 is =&gt; 'rw',
1849 default =&gt; sub { $highlander_bank },
1850);</code></pre>
1851</div>
1852
1853<div class="slide">
1854 <h1>Builder</h1>
1855
1856 <ul>
1857 <li>A method <em>name</em> which returns the default</li>
1858 </ul>
1859</div>
1860
1861<div class="slide">
1862 <h1>Builder</h1>
1863
1864 <pre><code>package Person;
1865use Moose;
1866
1867has bank =&gt; (
1868 is =&gt; 'rw',
1869 builder =&gt; '_build_bank',
1870);
1871
1872sub _build_bank {
1873 my $self = shift;
debc93f8 1874 return Bank-&gt;new(
1875 name => 'Spire FCU' );
8d1ce1d7 1876}</code></pre>
1877</div>
1878
1879<div class="slide">
1880 <h1>Default vs Builder</h1>
1881
1882 <ul>
1883 <li>Use default for simple scalars</li>
1884 <li>Use default to return empty references</li>
1885 <li>Use default for <em>very</em> trivial subroutine references</li>
1886 <li>Use builder for everything else</li>
1887 </ul>
1888</div>
1889
1890<div class="slide">
1891 <h1>Builder Bonuses</h1>
1892
1893 <ul>
1894 <li>Can be overridden and method modified, because it's called by <em>name</em></li>
1895 <li>Roles can require a builder</li>
1896 </ul>
1897</div>
1898
1899<div class="slide">
1900 <h1>Role Requires Builder</h1>
1901
1902 <pre><code>package HasBank;
1903use Moose::Role;
1904
1905requires '_build_bank';
1906
1907has bank =&gt; (
1908 is =&gt; 'ro',
1909 builder =&gt; '_build_bank',
1910);</code></pre>
1911</div>
1912
1913<div class="slide">
debc93f8 1914 <h1>Lazy, Good for Nothin' Attributes</h1>
8d1ce1d7 1915
1916 <ul>
1917 <li>Normally, defaults are generated during object construction</li>
1918 <li>This can be expensive</li>
1919 <li>We want to default to <code>$self-&gt;size * 2</code>, but attribute initialization order is unpredictable</li>
1920 <li>Use lazy attributes!</li>
1921 </ul>
1922</div>
1923
1924<div class="slide">
1925 <h1>The Power of Dynamic Defaults</h1>
1926
1927 <pre><code>package Person;
1928use Moose;
1929
1930has shoe_size =&gt; (
1931 is =&gt; 'ro',
1932);</code></pre>
1933</div>
1934
1935<div class="slide">
1936 <h1>The Power of Dynamic Defaults</h1>
1937
1938 <pre><code>has shoes =&gt; (
1939 is =&gt; 'ro',
1940 <span class="highlight">lazy =&gt; 1,</span>
1941 builder => '_build_shoes',
1942);
1943
1944sub _build_shoes {
1945 my $self = shift;
1946
1947 return Shoes-&gt;new(
13cb03c7 1948 size =&gt; <span class="highlight">$self-&gt;shoe_size</span> );
8d1ce1d7 1949}</code></pre>
1950</div>
1951
1952<div class="slide">
1953 <h1>Lazy is Good</h1>
1954
1955 <ul>
1956 <li>Lazy defaults are executed when the attribute is read</li>
1957 <li>Can see other object attributes</li>
1958 <li>Still need to watch out for circular laziness</li>
1959 </ul>
1960</div>
1961
1962<div class="slide">
1963 <h1>Clearer and Predicate</h1>
1964
1965 <ul>
1966 <li>Attributes can have a value, including <code>undef</code>, or not</li>
1967 <li>Can clear the value with a clearer method</li>
1968 <li>Can check for the existence of a value with a predicate method</li>
1969 <li>By default, these methods are not created</li>
1970 </ul>
1971</div>
1972
1973<div class="slide">
1974 <h1>Clearer and Predicate</h1>
1975
1976 <pre><code>package Person;
1977use Moose;
1978
1979has account =&gt; (
1980 is =&gt; 'ro',
1981 lazy =&gt; 1,
1982 builder =&gt; '_build_account',
1983 <span class="highlight">clearer =&gt; '_clear_account',
1984 predicate =&gt; 'has_account',</span>
1985);</code></pre>
1986</div>
1987
1988<div class="slide">
1989 <h1>Clearer and Lazy Defaults</h1>
1990
1991 <ul>
1992 <li>Lazy defaults are good for computed attributes</li>
1993 <li>Clear the attribute when the source data changes</li>
1994 <li>Recalculated at next access</li>
1995 </ul>
1996</div>
1997
1998<div class="slide">
1999 <h1>Renaming constructor arguments</h1>
2000
2001 <ul>
2002 <li>By default, constructor names = attribute names</li>
2003 <li>Use <code>init_arg</code> to change this</li>
2004 <li>Set <code>init_arg =&gt; undef</code> to make it unconstructable</li>
2005 </ul>
2006</div>
2007
2008<div class="slide">
2009 <h1>Some <code>init_arg</code> examples</h1>
2010
2011 <pre><code>package Person;
2012use Moose;
2013
2014has shoe_size => (
2015 is =&gt; 'ro',
2016 <span class="highlight">init_arg =&gt; 'foot_size',</span>
2017);
2018
2019Person->new( <span class="wrong">shoe_size =&gt; 13</span> );
2020
2021my $person =
2022 Person->new( <span class="right">foot_size =&gt; 13</span> );
2023print $person->shoe_size;</code></pre>
2024</div>
2025
2026<div class="slide">
2027 <h1>Some <code>init_arg</code> examples</h1>
2028
2029<pre><code>package Person;
2030use Moose;
2031
2032has shoes => (
2033 is =&gt; 'ro',
2034 <span class="highlight">init_arg =&gt; undef,</span>
2035);
2036
2037Person->new( <span class="wrong">shoes =&gt; Shoes-&gt;new</span> );</code></pre>
2038</div>
2039
2040<div class="slide">
2041 <h1>Why Set <code>init_arg =&gt; undef</code>?</h1>
2042
2043 <ul>
2044 <li>Use this with a lazy default for attributes-as-cache</li>
2045 <li>Compute the value as needed</li>
2046 <li>Ensure that it is always generated correctly (not set by constructor)</li>
2047 <li>Use triggers or method modifiers (coming soon) to clear the value</li>
2048 </ul>
2049</div>
2050
2051<div class="slide">
2052 <h1>Attribute Inheritance</h1>
2053
2054 <ul>
2055 <li>By default, subclasses inherit attribute as-is</li>
2056 <li>Can change some attribute parameters in subclasses
2057 <ul>
2058 <li>default</li>
2059 <li>builder</li>
2060 <li>required</li>
2061 <li>lazy</li>
2062 <li>others we've not yet covered</li>
2063 </ul>
2064 </li>
2065 </ul>
2066</div>
2067
2068<div class="slide">
2069 <h1>Attribute Inheritance Example</h1>
2070
2071 <pre><code>package Employee;
2072use Moose;
2073
2074extends 'Person';
2075
2076has '<span class="highlight">+first_name</span>' =&gt; (
2077 default =&gt; 'Joe',
2078);</code></pre>
2079</div>
2080
2081<div class="slide">
2082 <h1>Attribute Inheritance Warning</h1>
2083
2084 <ul>
2085 <li>An attribute is a contract about a class's API</li>
2086 <li>Don't break that contract in a subclass</li>
2087 <li>Especially important in the context of types</li>
2088 </ul>
2089</div>
2090
2091<div class="slide">
2092 <h1>Changing Accessor Names</h1>
2093
2094 <pre><code>package Person;
2095use Moose;
2096
2097has first_name =&gt; (
bd857054 2098 <span class="highlight">accessor</span> =&gt; 'first_name',
8d1ce1d7 2099);</code></pre>
2100
2101 <ul>
2102 <li>The long-hand version of <code>is =&gt; 'rw'</code></li>
2103 </ul>
2104</div>
2105
2106<div class="slide">
2107 <h1>Changing Accessor Names</h1>
2108
2109 <pre><code>package Person;
2110use Moose;
2111
2112has first_name =&gt; (
2113 <span class="highlight">reader</span> =&gt; 'first_name',
2114 <span class="highlight">writer</span> =&gt; undef,
2115);</code></pre>
2116
2117 <ul>
2118 <li>The long-hand version of <code>is =&gt; 'ro'</code></li>
2119 </ul>
2120</div>
2121
2122
2123<div class="slide">
2124 <h1>Changing Accessor Names</h1>
2125
2126 <pre><code>package Person;
2127use Moose;
2128
2129has first_name =&gt; (
2130 <span class="highlight">reader</span> =&gt; 'get_first_name',
de668480 2131 <span class="highlight">writer</span> =&gt; 'set_first_name',
8d1ce1d7 2132);</code></pre>
2133</div>
2134
2135<div class="slide">
2136 <h1>Changing Accessor Names</h1>
2137
2138 <pre><code>package Person;
2139use Moose;
2140
2141has first_name =&gt; (
2142 <span class="highlight">is</span> =&gt; 'rw',
2143 <span class="highlight">writer</span> =&gt; '_first_name',
2144);</code></pre>
2145
2146 <ul>
be6689d2 2147 <li>Can also mix-and-match <code>is</code> and explicit names</li>
8d1ce1d7 2148 </ul>
2149</div>
2150
2151<div class="slide">
2152 <h1>ETOOMUCHTYPING</h1>
2153
2154 <ul>
2155 <li><code>MooseX::FollowPBP</code><br /><code>get_foo</code> and <code>set_foo</code></li>
2156 <li><code>MooseX::SemiAffordanceAccessor</code><br /><code>foo</code> and <code>set_foo</code></li>
2157 </ul>
2158</div>
2159
2160<div class="slide">
2161 <h1>ETOOMUCHTYPING</h1>
2162
2163 <pre><code>package Person;
2164use Moose;
2165<span class="highlight">use MooseX::SemiAffordanceAccessor;</span>
2166
2167has first_name =&gt; (
2168 is =&gt; 'rw',
2169);</code></pre>
2170
2171 <ul>
2172 <li>Creates <code>first_name</code> and <code>set_first_name</code></li>
2173 </ul>
2174</div>
2175
2176<div class="slide">
26164c8d 2177 <h1>Basic Attributes Summary</h1>
2178
2179 <ul>
2180 <li>Attributes can be <code>required</code></li>
2181 <li>Attributes can have a <code>default</code> or <code>builder</code></li>
2182 <li>Attributes with a default or builder can be <code>lazy</code></li>
2183 <li>Attributes can have a <code>clearer</code> and/or <code>predicate</code></li>
2184 <li>An attribute's constructor name can be changed with <code>init_arg</code></li>
2185 <li>A subclass can alter its parents' attributes</li>
2186 <li>Attribute accessor names can be changed</li>
2187 </ul>
2188</div>
2189
2190<div class="slide">
2191 <h1>Questions?</h1>
2192</div>
2193
2194<div class="slide">
8d1ce1d7 2195 <h1>Exercises</h1>
2196
2197 <pre># cd exercises
debc93f8 2198# perl bin/prove -lv \
2199 t/03-basic-attributes.t
8d1ce1d7 2200
2201Iterate til this passes all its tests</pre>
2202</div>
2203
26164c8d 2204<div class="slide fake-slide0">
2205 <h1>Part 4: Method Modifiers</h1>
2206</div>
2207
2208<div class="slide">
2209 <h1>What is a Method Modifier</h1>
2210
2211 <ul>
2212 <li>Apply to an existing method</li>
2213 <li>... from a parent class, the current class, or a role</li>
2214 <li>Roles can provide modifiers that are applied at composition time</li>
2215 </ul>
2216</div>
2217
2218<div class="slide">
2219 <h1>What is a Method Modifier</h1>
2220
2221 <ul>
0a0c7e7c 2222 <li>"Inject" behavior</li>
26164c8d 2223 <li>Add behavior to generated methods (accessors, delegations)</li>
2224 <li>Provide roles which modify existing behavior</li>
2225 </ul>
2226</div>
2227
2228<div class="slide">
2229 <h1>Before and After</h1>
2230
2231 <ul>
2232 <li>Simplest modifiers - <code>before</code> and <code>after</code></li>
2233 <li>Guess when they run!</li>
2234 </ul>
2235</div>
2236
2237<div class="slide">
2238 <h1>Uses for <code>before</code></h1>
2239
2240 <ul>
2241 <li>As a pre-call check</li>
2242 </ul>
2243
2244 <pre><code>package Person;
2245use Moose;
2246
2247before work =&gt; sub {
2248 my $self = shift;
2249 die 'I have no job!'
2250 unless $self-&gt;has_title;
2251};</code></pre>
2252</div>
2253
2254<div class="slide">
2255 <h1>Uses for <code>before</code></h1>
2256
2257 <ul>
2258 <li>Logging/Debugging</li>
2259 </ul>
2260
2261 <pre><code>package Person;
2262use Moose;
2263
2264before work =&gt; sub {
2265 my $self = shift;
2266 return unless $DEBUG;
2267
debc93f8 2268 warn "Called work on ",
2269 $self-&gt;full_name,
26164c8d 2270 "with the arguments: [@_]\n";
2271};</code></pre>
2272</div>
2273
2274<div class="slide">
2275 <h1>Uses for <code>after</code></h1>
2276
2277 <ul>
2278 <li>Also works for logging/debugging</li>
2279 <li>Post-X side-effects (recording audit info)</li>
2280 </ul>
2281
2282 <pre><code>package Person;
2283use Moose;
2284
2285after work =&gt; sub {
2286 my $self = shift;
2287 $self-&gt;work_count(
2288 $self-&gt;work_count + 1 );
2289};</code></pre>
2290</div>
2291
2292<div class="slide">
2293 <h1>Other Uses</h1>
2294
2295 <ul>
2296 <li>Modifiers are useful for adding behavior to generated methods</li>
2297 </ul>
2298</div>
2299
2300<div class="slide">
debc93f8 2301 <h1>More Modifier Examples</h1>
26164c8d 2302
2303 <pre><code>has password =&gt; (
2304 is =&gt; 'rw',
2305 clearer =&gt; 'clear_password',
2306);
26164c8d 2307has hashed_password =&gt; (
2308 is =&gt; 'ro',
2309 builder =&gt; '_build_hashed_password',
2310 clearer =&gt; '_clear_hashed_password',
2311);
26164c8d 2312after clear_password =&gt; sub {
2313 my $self = shift;
2314 $self-&gt;_clear_hashed_password;
2315};</code></pre>
2316</div>
2317
2318<div class="slide">
2319 <h1><code>before</code> and <code>after</code> Limitations</h1>
2320
2321 <ul>
2322 <li>Cannot alter method parameters</li>
2323 <li>Cannot alter return value</li>
2324 <li>But <strong>can</strong> throw an exception</li>
2325 </ul>
2326</div>
2327
2328<div class="slide">
2329 <h1>The <code>around</code> Modifier</h1>
2330
2331 <ul>
2332 <li>The big gun</li>
2333 <li>Can alter parameters <strong>and/or</strong> return values</li>
2334 <li>Can skip calling the wrapped method entirely</li>
2335 </ul>
2336</div>
2337
2338<div class="slide">
2339 <h1>The power of <code>around</code></h1>
2340
2341 <pre><code>around insert =&gt; sub {
2342 my $orig = shift;
2343 my $self = shift;
2344
2345 $self-&gt;_validate_insert(@_);
2346
2347 my $new_user =
2348 $self-&gt;$orig(
2349 $self-&gt;_munge_insert(@_) );
2350
2351 $new_user->_assign_uri;
26164c8d 2352 return $new_user;
2353};</code></pre>
2354</div>
2355
2356<div class="slide">
2357 <h1>Modifier Order</h1>
2358
2359 <ul>
2360 <li>Before runs order from last to first</li>
2361 <li>After runs in order from first to last</li>
2362 <li>Around runs in order from last to first</li>
2363 </ul>
2364</div>
2365
2366<div class="slide">
2367 <h1>Modifier Order Illustrated</h1>
2368
2369<pre>
2370<span class="current incremental">before 2
2371 before 1</span>
2372 <span class="incremental">around 2
2373 around 1</span>
2374 <span class="incremental">wrapped method</span>
2375 <span class="incremental">around 1
2376 around 2</span>
2377 <span class="incremental">after 1
2378after 2</span>
2379</pre>
2380</div>
2381
2382<div class="slide">
2383 <h1>Modifiers in Roles</h1>
2384
2385 <ul>
2386 <li>Roles can use these modifiers</li>
2387 <li>Very powerful!</li>
2388 </ul>
2389</div>
2390
2391<div class="slide">
2392 <h1>Modifiers in Roles</h1>
2393
2394 <pre><code>package IsUnreliable;
2395use Moose::Role;
2396
2397<span class="highlight">requires 'run';
2398
2399around run</span> =&gt; sub {
2400 my $orig = shift;
2401 my $self = shift;
2402
2403 return if rand(1) &lt; 0.5;
2404
2405 return $self-&gt;$orig(@_);
2406};</code></pre>
2407</div>
2408
2409<div class="slide">
2410 <h1>Augment and Inner</h1>
2411
2412 <ul>
2413 <li>Inverted <code>super</code></li>
2414 <li>From least- to most-specific</li>
2415 <li>Grandparent to parent to child</li>
2416 <li>Not allowed in roles</li>
2417 </ul>
2418</div>
2419
2420<div class="slide">
2421 <h1>Augment and Inner</h1>
2422
2423 <pre><code>package Document;
2424
2425sub xml { '&lt;doc&gt;' . <span class="highlight">inner()</span> . '&lt;/doc&gt;' }
2426
2427package Report;
2428extends 'Document';
c3ccfa10 2429<span class="highlight">augment xml</span> =&gt;
2430 sub { title() . <span class="highlight">inner()</span> . summary() };
26164c8d 2431
2432package TPSReport;
2433extends 'Report';
c3ccfa10 2434<span class="highlight">augment xml</span> =&gt;
2435 sub { tps_xml() . <span class="highlight">inner()</span> };</code></pre>
26164c8d 2436</div>
2437
2438<div class="slide">
2439 <h1>Augment and Inner</h1>
2440
2441 <ul>
2442 <li>When we call <code>$tps-&gt;xml</code> ...
2443 <ul>
2444 <li><code>Document-&gt;xml</code></li>
2445 <li><code>Report-&gt;xml</code></li>
2446 <li><code>TPSReport-&gt;xml</code></li>
2447 </ul>
2448 </li>
2449 </ul>
2450</div>
2451
2452<div class="slide">
2453 <h1>Augment and Inner Usage</h1>
2454
2455 <ul>
2456 <li>Call <code>inner()</code> to "fill in the blank"</li>
2457 <li>Requires designing for subclassing</li>
2458 <li>Call <code>inner()</code> in the terminal class, just in case</li>
2459 </ul>
2460</div>
2461
2462<div class="slide">
5d572684 2463 <h1>Method Modifiers Summary</h1>
2464
2465 <ul>
2466 <li>Use <code>before</code> and <code>after</code> for ...
2467 <ul>
2468 <li>logging</li>
2469 <li>pre- or post-validation</li>
2470 <li>to add behavior to generated methods</li>
2471 </ul>
2472 </li>
2473 <li>These two modifiers cannot change parameters or return values</li>
2474 </ul>
2475</div>
2476
2477<div class="slide">
2478 <h1>Method Modifiers Summary</h1>
2479
2480 <ul>
2481 <li>Use <code>around</code> to ...
2482 <ul>
2483 <li>alter parameters passed to the original method</li>
2484 <li>alter the return value of the original method</li>
2485 <li>not call the original method at all (or call a <em>different</em> method)</li>
2486 </ul>
2487 </li>
2488 </ul>
2489</div>
2490
2491<div class="slide">
2492 <h1>Method Modifiers Summary</h1>
2493
2494 <ul>
2495 <li>When using modifiers in a role, require the modified method</li>
2496 <li>Use <code>augment</code> and <code>inner</code> to invert the normal subclassing flow ...
2497 <ul>
2498 <li>Least- to most-specific (parents to children)</li>
2499 <li>Build in "insertability" (stick more stuff in the "middle")</li>
2500 </ul>
2501 </li>
2502 <li>Always call <code>inner</code> in the most specific subclass to allow for future extension</li>
2503 </ul>
2504</div>
2505
2506<div class="slide">
26164c8d 2507 <h1>Questions?</h1>
2508</div>
2509
2510<div class="slide">
2511 <h1>Exercises</h1>
2512
2513 <pre># cd exercises
debc93f8 2514# perl bin/prove -lv \
2515 t/04-method-modifiers.t
26164c8d 2516
2517Iterate til this passes all its tests</pre>
2518</div>
2519
5d572684 2520<div class="slide fake-slide0">
2521 <h1>Part 5: Types</h1>
2522</div>
2523
636ceec1 2524<div class="slide">
2525 <h1>A Type System for Perl</h1>
2526
2527 <ul>
2528 <li>Sort of ...</li>
2529 <li><em>Variables</em> are not typed</li>
2530 <li>Attributes can have types</li>
2531 <li>MooseX modules let you define method signatures</li>
2532 </ul>
2533</div>
2534
2535<div class="slide">
2536 <h1>Components of a Moose Type</h1>
2537
2538 <ul>
2539 <li>A type is a name and a constraint</li>
2540 <li>Types have a hierarchy</li>
2541 <li>Constraints are cumulative from parents</li>
2542 <li>Types can have associated coercions</li>
2543 </ul>
2544</div>
2545
2546<div class="slide">
2547 <h1>Built-in Type Hierarchy</h1>
2548
2549 <pre>
2550Any
2551Item
2552 Bool
2553 Maybe[`a]
2554 Undef
2555 Defined
2556 Value
2557 Num
2558 Int
2559 Str
2560 ClassName
2561 RoleName
2562</pre>
2563</div>
2564
2565<div class="slide">
2566 <h1>Built-in Type Hierarchy</h1>
2567
2568<pre>
2569(Item)
2570 (Defined)
2571 Ref
2572 ScalarRef
2573 ArrayRef[`a]
2574 HashRef[`a]
2575 CodeRef
2576 RegexpRef
2577 GlobRef
2578 FileHandle
2579 Object
2580</pre>
2581</div>
2582
2583<div class="slide">
2584 <h1>Bool</h1>
2585
2586 <h2>True</h2>
2587 <pre><code>1
2588924.1
2589'true'
2590{}</code></pre>
2591
2592 <h2>False</h2>
2593 <pre><code>0
25940.0
2595'0'
2596undef</code></pre>
2597
2598 <ul>
2599 <li>Like Perl's <code>if ($foo)</code></li>
2600 </ul>
2601</div>
2602
2603<div class="slide">
2604 <h1>Value (and subtypes)</h1>
2605
2606 <ul>
b59551bc 2607 <li><code>Value</code> is true when <code>! ref $thing</code></li>
2608 <li><code>Value</code> and <code>Str</code> are effectively the same, but <code>Str</code> is more expressive</li>
636ceec1 2609 <li>An overloaded object which numifies does not pass the <code>Num</code> constraint!</li>
2610 <li>Perl 5's overloading is hopelessly broken</li>
2611 </ul>
2612</div>
2613
2614<div class="slide">
2615 <h1>ClassName and RoleName</h1>
2616
2617 <ul>
2618 <li>A string with a package name</li>
2619 <li>The package <strong>must already be loaded</strong></li>
2620 </ul>
2621</div>
2622
2623<div class="slide">
2624 <h1>Parameterizable Types</h1>
2625
2626 <ul>
2627 <li>What does <code>ArrayRef[`a]</code> mean?</li>
2628 <li><code>s/`a/Int/</code> (or <code>Str</code> or ...)</li>
2629 <li>When you use it you can write ...
2630 <ul>
2631 <li><code>ArrayRef</code> (== <code>ArrayRef[Item]</code>)</li>
2632 <li><code>ArrayRef[Str]</code></li>
2633 <li><code>ArrayRef[MyTypeName]</code></li>
2634 <li><code>ArrayRef[HashRef[Maybe[Int]]]</code></li>
2635 </ul>
2636 </li>
2637 </ul>
2638</div>
2639
2640<div class="slide">
2641 <h1>Maybe[`a]</h1>
2642
2643 <ul>
2644 <li>Maybe means either the named type or <code>undef</code></li>
2645 <li><code>Maybe[Int]</code> accepts integers or <code>undef</code></li>
2646 </ul>
2647</div>
2648
2649<div class="slide">
b59551bc 2650 <h1>Type Union</h1>
636ceec1 2651
2652 <ul>
2653 <li>This or that (or that or ...)</li>
2654 <li><code>Int | ArrayRef[Int]</code></li>
2655 <li>But use a coercion instead when possible</li>
b59551bc 2656 <li>Or use a <code>role_type</code>, <code>duck_type</code>, or anything not a union</li>
2657 <li>A union is often a code smell</li>
636ceec1 2658 </ul>
2659</div>
2660
2661<div class="slide">
2662 <h1>Making Your Own Types</h1>
2663
2664 <pre><code>use Moose::Util::TypeConstraints;
2665
2666<span class="incremental current">subtype 'PositiveInt',</span>
2667 <span class="incremental">as 'Int',</span>
2668 <span class="incremental">where { $_ &gt; 0 },</span>
debc93f8 2669 <span class="incremental">message
2670 { "The value you provided ($_)"
2671 . " was not a positive int." };</span>
636ceec1 2672
2673has size =&gt; (
2674 is =&gt; 'ro',
2675 <span class="incremental">isa =&gt; 'PositiveInt',</span>
2676);</code></pre>
2677</div>
2678
2679<div class="slide">
2680 <h1>Automatic Types</h1>
2681
2682 <ul>
2683 <li>Moose creates a type for every Moose class and role</li>
2684 <li>Unknown names are assumed to be classes</li>
2685 </ul>
2686</div>
2687
2688<div class="slide">
2689 <h1>Automatic Types</h1>
2690
2691 <pre><code>package Employee;
2692use Moose;
2693
2694has manager =&gt; (
2695 is =&gt; 'rw',
2696 <span class="highlight">isa =&gt; 'Employee',</span>
2697);
2698
2699has start_date =&gt; (
2700 is =&gt; 'ro',
2701 <span class="highlight">isa =&gt; 'DateTime',</span>
2702);</code></pre>
2703</div>
2704
2705<div class="slide">
2706 <h1>Subtype Shortcuts - <code>class_type</code></h1>
2707
2708 <pre><code>use Moose::Util::TypeConstraints;
2709class_type 'DateTime';
2710
2711subtype 'DateTime',
2712 as 'Object',
2713 where { $_-&gt;isa('DateTime') },
2714 message { ... };</code></pre>
2715</div>
2716
2717<div class="slide">
2718 <h1>Subtype Shortcuts - <code>role_type</code></h1>
2719
2720 <pre><code>use Moose::Util::TypeConstraints;
2721role_type 'Printable';
2722
2723subtype 'Printable',
2724 as 'Object',
2725 where
2726 { Moose::Util::does_role(
2727 $_, 'Printable' ) },
2728 message { ... };</code></pre>
2729</div>
2730
2731<div class="slide">
2732 <h1>Subtype Shortcuts - <code>duck_type</code></h1>
2733
2734 <pre><code>use Moose::Util::TypeConstraints;
2735duck_type Car =&gt; qw( run break_down );
2736
2737subtype 'Car',
2738 as 'Object',
2739 where { all { $_-&gt;can($_) }
2740 qw( run break_down ) },
2741 message { ... };</code></pre>
2742</div>
2743
2744<div class="slide">
2745 <h1>Subtype Shortcuts - <code>enum</code></h1>
2746
2747 <pre><code>use Moose::Util::TypeConstraints;
2748enum Color =&gt; qw( red blue green ) );
2749
debc93f8 2750my %ok = map { $_ =&gt; 1 }
2751 qw( red blue green );
2752
636ceec1 2753subtype 'Color'
2754 as 'Str',
2755 where { $ok{$_} },
2756 message { ... };</code></pre>
2757</div>
2758
2759<div class="slide">
2760 <h1>Anonymous Subtypes</h1>
2761
2762 <pre><code>package Person;
2763
2764<span class="highlight">my $posint =
2765 subtype as 'Int', where { $_ &gt; 0 };</span>
2766
2767has size =&gt; (
2768 is =&gt; 'ro',
2769 <span class="highlight">isa =&gt; $posint,</span>
2770);</code></pre>
2771
2772 <ul>
2773 <li>Shortcuts have anonymous forms as well</li>
2774 </ul>
2775</div>
2776
2777<div class="slide">
2778 <h1>Coercions</h1>
2779
2780 <pre><code>use Moose::Util::TypeConstraints;
2781
2782subtype 'UCStr',
2783 as 'Str',
debc93f8 2784 where { ! /[a-z]/ };</code></pre>
2785</div>
2786
2787<div class="slide">
2788 <h1>Coercions</h1>
636ceec1 2789
debc93f8 2790 <pre><code><span class="incremental current">coerce 'UCStr',</span>
636ceec1 2791 <span class="incremental">from 'Str',</span>
2792 <span class="incremental">via { uc };</span>
2793
2794has shouty_name =&gt; (
2795 is =&gt; 'ro',
2796 isa =&gt; 'UCStr',
2797 <span class="incremental">coerce =&gt; 1,</span>
2798);</code></pre>
2799</div>
2800
2801<div class="slide">
b59551bc 2802 <h1>Coercion Examples</h1>
2803
2804 <pre><code>subtype 'My::DateTime',
2805 as class_type 'DateTime';
2806
2807coerce 'My::DateTime',
2808 from 'HashRef',
2809 via { DateTime-&gt;new( %{$_} ) };
2810
2811coerce 'My::DateTime',
2812 from 'Int',
2813 via { DateTime-&gt;from_epoch(
2814 epoch =&gt; $_ ) };</code></pre>
2815
2816 <ul>
2817 <li>Use coercion to inflate a value</li>
2818 </ul>
2819</div>
2820
2821<div class="slide">
2822 <h1>Coercion Examples</h1>
2823
2824 <pre><code>coerce 'ArrayRef[Int]',
2825 from 'Int',
2826 via { [ $_ ] };</code></pre>
2827
2828 <ul>
2829 <li>Coerce instead of a union like <code style="white-space: nowrap">Int | ArrayRef[Int]</code></li>
2830 </ul>
2831</div>
2832
b59551bc 2833<div class="slide">
2834 <h1>Using Types with Attributes</h1>
2835
2836 <pre><code>package Person;
2837
b59551bc 2838has height =&gt; (
2839 is =&gt; 'rw',
2840 <span class="highlight">isa =&gt; 'Num',</span>
2841);
2842
2843has favorite_numbers =&gt; (
2844 is =&gt; 'rw',
2845 <span class="highlight">isa =&gt; 'ArrayRef[Int]',
2846 coerce =&gt; 1,</span>
2847);</code></pre>
2848</div>
2849
2850<div class="slide">
ee2e815e 2851 <h1>More Droppings</h1>
2852
2853 <ul>
2854 <li><code>Moose::Util::TypeConstraint</code> also needs cleanup</li>
2855 </ul>
2856
2857 <pre><code>package Person;
2858
2859use Moose;
2860use Moose::Util::TypeConstraints;
2861
2862subtype ...;
2863
2864no Moose;
2865<span class="highlight">no Moose::Util::TypeConstraints;</span></code></pre>
2866</div>
2867
2868<div class="slide">
b59551bc 2869 <h1>Typed Methods (Low-tech)</h1>
2870
2871 <pre class="medium"><code>package Person;
2872<span class="highlight">use MooseX::Params::Validate qw( validated_list );</span>
2873
2874sub work {
2875 my $self = shift;
2876 <span class="highlight">my ( $tasks, $can_rest ) =
2877 validated_list(
2878 \@_,
2879 tasks =&gt;
2880 { isa =&gt; 'ArrayRef[Task]',
2881 coerce =&gt;1 },
2882 can_rest =&gt;
2883 { isa =&gt; 'Bool',
2884 default =&gt; 0 },
2885 );</span>
b59551bc 2886 ...
2887}</code></pre>
68af922f 2888</div>
b59551bc 2889
2890<div class="slide">
2891 <h1>Typed Methods (High-tech)</h1>
2892
2893 <pre class="medium"><code>package Person;
2894
2895<span class="highlight">use MooseX::Method::Signatures;</span>
2896
2897<span class="highlight">method work ( ArrayRef[Task] :$tasks,
2898 Bool :$can_rest = 0 )</span> {
2899 my $self = shift;
2900
2901 ...
2902}</code></pre>
68af922f 2903</div>
b59551bc 2904
2905<div class="slide">
636ceec1 2906 <h1>Digression: The Type Registry</h1>
2907
2908 <ul>
2909 <li>Types are actually <code>Moose::Meta::TypeConstraint</code> <em>objects</em></li>
2910 <li>Stored in an interpreter-global registry mapping names to objects</li>
2911 </ul>
2912</div>
2913
2914<div class="slide">
2915 <h1>Danger!</h1>
2916
2917 <ul>
2918 <li>Coercions are attached to type objects</li>
2919 <li>Therefore also global</li>
2920 <li>Name conflicts between modules!</li>
2921 <li>Coercion conflicts between modules!</li>
2922 </ul>
2923</div>
2924
2925<div class="slide">
b59551bc 2926 <h1>Namespace Fix</h1>
636ceec1 2927
2928 <ul>
2929 <li>Use some sort of pseudo-namespacing scheme</li>
2930 <li>Never coerce directly to a class name, or <em>to</em> built-in types</li>
2931 </ul>
2932</div>
2933
2934<div class="slide">
2935 <h1>Namespace Fix</h1>
2936
2937 <pre><code>use Moose::Util::TypeConstraints;
636ceec1 2938subtype <span class="highlight">'MyApp::Type::DateTime',</span>
2939 as 'DateTime';
2940
2941<span class="highlight">coerce 'MyApp::Type::DateTime',</span>
2942 from 'HashRef',
2943 via { DateTime-&gt;new( %{$_} ) }
2944
2945has creation_date =&gt; (
2946 is =&gt; 'ro',
2947 <span class="highlight">isa =&gt; 'MyApp::Type::DateTime',</span>
2948 coerce =&gt; 1,
2949);</code></pre>
2950</div>
2951
2952<div class="slide">
2953 <h1>Namespace Fix</h1>
2954
2955 <pre><code>subtype 'MyApp::Type::ArrayOfInt',
2956 as 'ArrayRef[Int]';
2957
2958coerce 'MyApp::Type::ArrayOfInt',
2959 from 'Int',
2960 via { [ $_ ] };</code></pre>
2961</div>
636ceec1 2962
2963<div class="slide">
b59551bc 2964 <h1>Namespace Fix Pros and Cons</h1>
636ceec1 2965
b59551bc 2966 <ul>
2967 <li><span class="right">Relatively simple</span></li>
2968 <li><span class="right">Already built into Moose</span></li>
2969 <li><span class="wrong">Conflates type and module namespaces</span></li>
2970 <li><span class="wrong">Type names are strings, so typos are easy to make and may be hard to find</span></li>
2971 </ul>
2972</div>
636ceec1 2973
b59551bc 2974<div class="slide">
2975 <h1>MooseX::Types</h1>
636ceec1 2976
b59551bc 2977 <pre><code>package MyApp::Types;
2978
2979use MooseX::Types
2980 <span class="highlight">-declare =&gt; [ qw( ArrayOfInt ) ]</span>;
2981use MooseX::Types::Moose
2982 qw( ArrayRef Int );
2983
2984subtype <span class="highlight">ArrayOfInt</span>,
2985 as ArrayRef[Int];
2986
2987coerce <span class="highlight">ArrayOfInt</span>
2988 from Int,
2989 via { [ $_ ] };</code></pre>
2990</div>
2991
2992<div class="slide">
2993 <h1>MooseX::Types</h1>
2994
2995 <pre><code>package MyApp::Account;
2996
2997use MyApp::Types qw( ArrayOfInt );
2998
2999has transaction_history => (
3000 is => 'rw',
3001 isa => ArrayOfInt,
3002);</code></pre>
68af922f 3003</div>
b59551bc 3004
3005<div class="slide">
3006 <h1>MooseX::Types</h1>
636ceec1 3007
3008 <ul>
b59551bc 3009 <li>Type names are exported functions, catches typos early</li>
3010 <li>Types must be pre-declared</li>
3011 <li>Types are stored with namespaces internally, but externally are short</li>
3012 <li>Import existing Moose types as functions from <code>MooseX::Types::Moose</code></li>
3013 <li>Still need string names for things like <code>ArrayRef['Email::Address']</code></li>
636ceec1 3014 </ul>
3015</div>
3016
3017<div class="slide">
b59551bc 3018 <h1>MooseX::Types Pros and Cons</h1>
636ceec1 3019
b59551bc 3020 <ul>
3021 <li><span class="right">Catches typos at compile time</span></li>
3022 <li><span class="right">Automatic namespacing</span></li>
3023 <li><span class="wrong">One more thing to install and learn</span></li>
3024 <li><span class="wrong">Every name gets types twice (declared and then defined)</span></li>
3025 <li><span class="wrong">Still stuck with strings when referring to class or role names</span></li>
68af922f 3026 <li><span class="wrong">Coercion gotcha from earlier still applies to types exported from <code>MooseX::Types::Moose</code></span></li>
b59551bc 3027 </ul>
3028</div>
3029
3030<div class="slide">
3031 <h1>Recommendation</h1>
636ceec1 3032
3033 <ul>
b59551bc 3034 <li>Use <code>MooseX::Types</code></li>
3035 <li>Compile time error catching and automatic namespacing are huge wins</li>
3036 <li>Docs from <code>Moose::Util::TypeConstraints</code> are 98% compatible with <code>MooseX::Types</code> anyway</li>
3037 <li>A function exported by a type library works wherever a type name would</li>
636ceec1 3038 </ul>
3039</div>
3040
3041<div class="slide">
3042 <h1>Questions?</h1>
3043</div>
3044
3045<div class="slide">
3046 <h1>Exercises</h1>
3047
3048 <pre># cd exercises
3049# perl bin/prove -lv t/05-types.t
3050
3051Iterate til this passes all its tests</pre>
3052</div>
3053
5d572684 3054<div class="slide fake-slide0">
3055 <h1>Part 6: Advanced Attributes</h1>
3056</div>
3057
3058<div class="slide">
3059 <h1>Weak References</h1>
3060
3061 <ul>
3062 <li>A weak reference lets you avoid circular references</li>
3063 <li>Weak references do not increase the reference count</li>
3064 </ul>
3065</div>
3066
3067<div class="slide">
3068 <h1>Circular Reference Illustrated</h1>
3069
3070 <pre><code>my $foo = {};
3071my $bar = { foo =&gt; $foo };
3072$foo-&gt;{bar} = $bar;</code></pre>
3073
3074 <ul>
3075 <li>Neither <code>$foo</code> nor <code>$bar</code> go out of scope<br />
3076 (until the program exits)</li>
3077 </ul>
3078</div>
3079
3080<div class="slide">
3081 <h1>Weakening Circular References</h1>
3082
3083 <pre><code>use Scalar::Util qw( weaken );
3084
3085my $foo = {};
3086my $bar = { foo =&gt; $foo };
3087$foo-&gt;{bar} = $bar;
3088weaken $foo-&gt;{bar}</code></pre>
3089
3090 <ul>
3091 <li>When <code>$bar</code> goes out of scope, <code>$foo-&gt;{bar}</code> becomes <code>undef</code></li>
3092 </ul>
3093</div>
3094
3095<div class="slide">
3096 <h1>Circular References in Attributes</h1>
3097
3098 <pre><code>package Person;
3099use Moose;
3100
3101has name =&gt; ( is =&gt; 'ro' );
3102has friend =&gt; ( is =&gt; 'rw' );
3103
3104my $alice = Person-&gt;new( name =&gt; 'Alice' );
3105my $bob = Person-&gt;new( name =&gt; 'Bob' );
3106$bob-&gt;friend($alice);
3107$alice-&gt;friend($bob);</code></pre>
3108</div>
3109
3110<div class="slide">
3111 <h1>The Fix</h1>
3112
3113 <pre><code>package Person;
3114use Moose;
3115
3116has name =&gt; ( is =&gt; 'ro' );
debc93f8 3117has friend =&gt; ( is =&gt; 'rw',
3118 <span class="highlight">weak_ref =&gt; 1</span> );
5d572684 3119
3120my $alice = Person-&gt;new( name =&gt; 'Alice' );
3121my $bob = Person-&gt;new( name =&gt; 'Bob' );
3122$bob-&gt;friend($alice);
3123$alice-&gt;friend($bob);</code></pre>
3124</div>
3125
3126<div class="slide">
3127 <h1>Under the Hood</h1>
3128
3129 <ul>
3130 <li>A <code>weak_ref</code> attribute calls <code>weaken</code> ...
3131 <ul>
3132 <li>during object construction</li>
3133 <li>when the attribute is set via a writer</li>
3134 </ul>
3135 </li>
3136 </ul>
3137</div>
3138
3139<div class="slide">
3140 <h1>Triggers</h1>
3141
3142 <ul>
3143 <li>A code reference run after an attribute is <em>set</em></li>
3144 <li>Like an <code>after</code> modifier, but makes intentions clearer</li>
3145 </ul>
3146
3147 <h2 class="wrong">Gross</h2>
3148
3149 <pre><code>after salary_level =&gt; {
3150 my $self = shift;
3151 return unless @_;
3152 $self-&gt;clear_salary;
3153};</code></pre>
3154</div>
3155
3156<div class="slide">
3157 <h1>Use a Trigger Instead</h1>
3158
3159 <h2 class="right">Cleaner</h2>
3160
3161 <pre><code>has salary_level =&gt; (
3162 is =&gt; 'rw',
3163 trigger =&gt; sub { $_[0]-&gt;clear_salary },
3164);</code></pre>
3165</div>
3166
3167<div class="slide">
3168 <h1>Delegation</h1>
3169
3170 <ul>
3171 <li>Attributes can be objects</li>
3172 <li>Delegation transparently calls methods on those objects</li>
3173 </ul>
3174</div>
3175
3176<div class="slide">
3177 <h1>Delegation Examples</h1>
3178
3179 <pre><code>package Person;
3180
3181has lungs =&gt; (
3182 is =&gt; 'ro',
3183 isa => 'Lungs',
3184 <span class="highlight">handles =&gt; [ 'inhale', 'exhale' ],</span>
3185);</code></pre>
3186
3187 <ul>
3188 <li>Creates <code>$person-&gt;inhale</code> and <code>-&gt;exhale</code> methods</li>
3189 <li>Internally calls <code>$person-&gt;lungs-&gt;inhale</code></li>
3190 </ul>
3191</div>
3192
3193<div class="slide">
3194 <h1>Why Delegation?</h1>
3195
3196 <ul>
3197 <li>Reduce the number of classes exposed</li>
3198 <li>Re-arrange class internals -<br />
3199 turn a method into an attribute with delegation</li>
3200 <li>Provide convenenience methods</li>
3201 </ul>
3202</div>
3203
3204<div class="slide">
3205 <h1>Moose's <code>handles</code> Parameter</h1>
3206
3207 <ul>
3208 <li>Accepts many arguments ...
3209 <ul>
3210 <li>Array reference - list of methods to delegate as-is</li>
3211 <li>Hash reference - map of method names</li>
3212 <li>Regex - delegates all matching methods</li>
3213 <li>Role name - delegates all methods in the role</li>
3214 <li>Sub reference - does something complicated ;)</li>
3215 </ul>
3216 </li>
3217 </ul>
3218</div>
3219
3220<div class="slide">
3221 <h1>Array Reference</h1>
3222
3223 <ul>
3224 <li>Takes each method name and creates a simple delegation from the delegating class to the delegatee attribute</li>
3225 </ul>
3226</div>
3227
3228<div class="slide">
3229 <h1>Hash Reference</h1>
3230
3231 <ul>
3232 <li>Mapping of names in the delegating class to the delegatee class</li>
3233 </ul>
3234
3235 <pre><code>package Person;
3236use Moose;
5d572684 3237has account =&gt; (
3238 is =&gt; 'ro',
3239 isa =&gt; 'BankAccount',
3240 <span class="highlight">handles =&gt; {
3241 receive_money =&gt; 'deposit',
3242 give_money =&gt; 'withdraw',
3243 },</span>
3244);</code></pre>
3245</div>
3246
3247<div class="slide">
3248 <h1>Hash Reference Detailed</h1>
3249
3250 <pre><code> handles =&gt; {
3251 receive_money =&gt; 'deposit',
3252 give_money =&gt; 'withdraw',
3253 },</code></pre>
3254
3255 <ul>
3256 <li><code>$person-&gt;receive_money</code> = <code>$person-&gt;account-&gt;deposit</code></li>
3257 <li><code>$person-&gt;give_money</code> = <code>$person-&gt;account-&gt;withdraw</code></li>
3258 </ul>
3259</div>
3260
3261<div class="slide">
3262 <h1>Regex</h1>
3263
3264 <pre><code>package Person;
3265use Moose;
3266
3267has name =&gt; (
3268 is =&gt; 'ro',
3269 isa =&gt; 'Name',
3270 handles =&gt; qr/.*/,
3271);</code></pre>
3272
3273 <ul>
3274 <li>Creates a delegation for every method in the Name class</li>
3275 <li>Excludes <code>meta</code> and methods inherited from <code>Moose::Object</code></li>
3276 </ul>
3277</div>
3278
3279<div class="slide">
3280 <h1>Role Name</h1>
3281
3282 <pre><code>package Auditor;
3283use Moose::Role;
5d572684 3284sub record_change { ... }
3285sub change_history { ... }
3286
3287package Account;
3288use Moose;
3289
3290has history =&gt; (
3291 is =&gt; 'ro',
3292 does =&gt; 'Auditor',
3293 <span class="highlight">handles =&gt; 'Auditor',</span>
3294);</code></pre>
3295</div>
3296
3297<div class="slide">
3298 <h1>Role Name Detailed</h1>
3299
3300 <ul>
3301 <li>Account gets delegate methods for each method in the <code>Auditor</code> role
3302 <ul>
3303 <li>record_history</li>
3304 <li>change_history</li>
3305 </ul>
3306 </li>
3307 </ul>
3308</div>
3309
3310<div class="slide">
1c32806a 3311 <h1>Native Delegation</h1>
3312
3313 <ul>
3314 <li>Delegate to <em>unblessed</em> Perl types</li>
3315 <li>Scalar, array or hash ref, etc</li>
3316 </ul>
3317</div>
3318
3319<div class="slide">
3320 <h1>Native Delegation - Array</h1>
3321
3322 <pre><code>package Person;
3323use Moose;
1c32806a 3324has _favorite_numbers =&gt; (
3325 traits =&gt; [ 'Array' ],
3326 is =&gt; 'ro',
3327 isa =&gt; 'ArrayRef[Int]',
3328 default =&gt; sub { [] },
3329 init_arg =&gt; undef,
3330 <span class="highlight">handles =&gt;
3331 { favorite_numbers =&gt; 'elements',
3332 add_favorite_number =&gt; 'push',
3333 },</span>
3334);</code></pre>
1c32806a 3335</div>
3336
3337<div class="slide">
3338 <h1>Native Delegation - Counter</h1>
3339
3340 <pre><code>package Stack;
3341use Moose;
1c32806a 3342has depth =&gt; (
3343 traits =&gt; [ 'Counter' ],
3344 is =&gt; 'ro',
3345 isa =&gt; 'Int',
3346 default =&gt; 0,
3347 init_arg =&gt; undef,
3348 <span class="highlight">handles =&gt;
3349 { _inc_depth =&gt; 'inc',
3350 _dec_depth =&gt; 'dec',
3351 },</span>
3352);</code></pre>
3353</div>
3354
3355
3356<div class="slide">
5d572684 3357 <h1>Traits and Metaclasses</h1>
3358
3359 <ul>
3360 <li>The ultimate in customization</li>
3361 <li>Per attribute metaclasses</li>
3362 <li>Per attribute roles applied to the attribute metaclass</li>
3363 <li>Change the meta-level behavior</li>
3364 </ul>
3365</div>
3366
3367<div class="slide">
3368 <h1>Traits and Metaclasses</h1>
3369
3370 <ul>
3371 <li>The default metaclass is <code>Moose::Meta::Attribute</code></li>
3372 <li>Controls accessor generation, defaults, delegation, etc.</li>
3373 <li>Adding a role to this metaclass (or replacing it) allows for infinite customization</li>
3374 </ul>
3375</div>
3376
3377<div class="slide">
3378 <h1>Traits and Metaclasses</h1>
3379
3380 <ul>
3381 <li>Can add/alter/remove attribute parameter (from <code>has</code>)</li>
3382 <li>Can change behavior of created attribute</li>
3383 </ul>
3384</div>
3385
3386<div class="slide">
3387 <h1>Simple Trait Example</h1>
3388
3389 <pre><code>package Person;
3390use Moose;
3391use MooseX::LabeledAttributes;
3392
3393has ssn =&gt; (
3394 <span class="highlight">traits =&gt; [ 'Labeled' ],</span>
3395 is =&gt; 'ro',
3396 isa =&gt; 'Str',
3397 <span class="highlight">label =&gt; 'Social Security Number',</span>
3398);
5d572684 3399print <span class="highlight">Person-&gt;meta
3400 -&gt;get_attribute('ssn')-&gt;label;</span></code></pre>
3401</div>
3402
3403<div class="slide">
3404 <h1>Simple Metaclass Example</h1>
3405
3406 <pre><code>package Person;
3407use Moose;
3408use MooseX::LabeledAttributes;
3409
3410has ssn =&gt; (
3411 <span class="highlight">metaclass =&gt;
3412 'MooseX::Meta::Attribute::Labeled',</span>
3413 is =&gt; 'ro',
3414 isa =&gt; 'Str',
3415 <span class="highlight">label =&gt; 'Social Security Number',</span>
3416);
5d572684 3417print <span class="highlight">Person-&gt;meta
3418 -&gt;get_attribute('ssn')-&gt;label;</span></code></pre>
3419</div>
3420
3421<div class="slide">
3422 <h1>Traits vs Metaclass</h1>
3423
3424 <ul>
3425 <li>Can apply any mix of traits to an attribute</li>
3426 <li>But just one metaclass</li>
3427 <li>Traits (aka roles) can cooperate</li>
3428 <li>Metaclasses require you to pick just one</li>
3429 </ul>
3430</div>
3431
3432<div class="slide">
3433 <h1>Advanced Attributes Summary</h1>
3434
3435 <ul>
3436 <li>Use <code>weak_ref</code> to avoid circular references</li>
3437 <li>Use trigger to do an action post-attribute write</li>
3438 <li>Use delegations to hide "internal" objects</li>
3439 <li>Traits and metaclasses let you extend Moose's core attribute features</li>
3440 </ul>
3441</div>
3442
9186987b 3443<div class="slide">
3444 <h1>Questions?</h1>
3445</div>
3446
3447<div class="slide">
3448 <h1>Exercises</h1>
3449
3450 <pre># cd exercises
debc93f8 3451# perl bin/prove -lv \
3452 t/06-advanced-attributes.t
9186987b 3453
3454Iterate til this passes all its tests</pre>
3455</div>
3456
3457<div class="slide fake-slide0">
3458 <h1>Part 7: Introspection</h1>
3459</div>
3460
3461<div class="slide fake-slide0">
3462 <h1>Part 8: A Tour of MooseX</h1>
3463</div>
3464
3465<div class="slide fake-slide0">
3466 <h1>Part 9: Writing Moose Extensions</h1>
3467</div>
3468
8a719516 3469<div class="slide fake-slide0">
5e2eb691 3470 <h1>The End</h1>
8a719516 3471</div>
3472
3473<div class="slide">
3474 <h1>More Information</h1>
3475
3476 <ul>
3477 <li><a href="http://moose.perl.org/">http://moose.perl.org/</a></li>
3478 <li><a href="http://search.cpan.org/dist/Moose/lib/Moose/Manual.pod">Moose::Manual</a> and <a href="http://search.cpan.org/dist/Moose/lib/Moose/Cookbook.pod">Moose::Cookbook</a></li>
3479 <li><a href="irc://irc.perl.org/#moose">irc://irc.perl.org/#moose</a></li>
3480 <li>mailing list - <a href="mailto:moose@perl.org">moose@perl.org</a></li>
3481 <li>Slides and exercises are in Moose's git repo:
3482 <br />
5e2eb691 3483 <span style="white-space: nowrap">git://jules.scsys.co.uk/gitmo/moose-presentations</span></li>
8a719516 3484 </ul>
3485</div>
3486
55906a14 3487</div>
b751d33f 3488</body>
3489</html>
55906a14 3490
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3493Copyright 2009 David Rolsky. All Rights Reserved.
3494
3495This work is licensed under a Creative Commons Attribution-Share Alike
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