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4
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6<title>Introduction to Moose</title>
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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>
129 <li>Access-control (read-only vs read-write)</li>
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
238 return ( @return, 'modify return values' );
239};</code></pre>
240</div>
241
242<div class="slide">
243 <h1>Type Constraints</h1>
244
245 <ul>
246 <li>NOT A FULL-BLOWN TYPE SYSTEM!</li>
247 <li>But still darn useful</li>
248 <li>Constrain attribute values</li>
249 <li>Coerce from other types</li>
250 </ul>
251</div>
252
253<div class="slide">
254 <h1>Type Constraint Example</h1>
255
256<pre><code>package Person;
257use Moose;
258
55906a14 259has weight =&gt; (
260 is =&gt; 'ro',
261 <span class="highlight">isa =&gt; 'Int'</span>,
262);
b751d33f 263
264# kaboom
265Person-&gt;new( weight =&gt; 'fat' );</code></pre>
266</div>
267
268<div class="slide">
269 <h1>Delegation</h1>
270
271 <ul>
272 <li>Attributes can define delegations</li>
273 <li>Lets you hide some implementation details</li>
274 <li>Fewer objects to chase around</li>
275 </ul>
276</div>
277
278<div class="slide">
279 <h1>Delegation</h1>
280
281<pre><code>package Person;
282use Moose;
283
55906a14 284has blog_uri =&gt; (
b751d33f 285 is =&gt; 'rw',
286 isa =&gt; 'URI',
287 <span class="highlight">handles =&gt; { 'blog_hostname' =&gt; 'host' },</span>
288);
289
290<span class="highlight">$person->blog_hostname;</span>
55906a14 291# really calls $person->blog_uri->host</code></pre>
b751d33f 292</div>
293
294<div class="slide">
295 <h1>Constructors</h1>
296
297 <ul>
298 <li>Moose creates <code>new()</code> for you</li>
299 <li>Provide an optional <code>BUILDARGS()</code> and <code>BUILD()</code></li>
300 </ul>
301</div>
302
303<div class="slide">
304 <h1>Destructors</h1>
305
306 <ul>
307 <li>Provide an optional <code>DEMOLISH()</code></li>
308 </ul>
309</div>
310
311<div class="slide">
312 <h1>Moose Meta-API</h1>
313
314 <ul>
315 <li>Answers questions like ...
316 <ul>
317 <li>What methods does this class have?</li>
318 <li>What are its parents?</li>
319 <li>What attributes does it have (including inherited attributes)?</li>
320 <li>What roles does it do?</li>
321 <li>Much, much, more</li>
322 </ul>
323 </li>
324 </ul>
325</div>
326
327<div class="slide">
328 <h1>Moose Meta-API</h1>
329
330 <ul>
331 <li>Not just for introspection ...
332 <ul>
333 <li>Add methods, attributes, roles, etc</li>
334 <li>Extend and alter core features</li>
335 </ul>
336 </li>
337 </ul>
338</div>
339
340<div class="slide">
341 <h1>Why Moose?</h1>
342
343 <ul>
811952b2 344 <li>A quick bit of propaganda ...</li>
b751d33f 345 </ul>
346</div>
347
348<div class="slide">
349 <h1>With Moose</h1>
350
351 <pre><code>package Person;
352use Moose;
353
354has last_name =&gt; (
355 is =&gt; 'rw',
356 isa =&gt; 'Str',
357);</code></pre>
358</div>
359
360<div class="slide">
361 <h1>Without Moose</h1>
362
363 <pre class="small"><code>package Person;
364use strict;
365use warnings;
366use Carp 'confess';
367
368sub new {
369 my $class = shift;
370 my %args = @_;
371 my $self = {};
372
373 if (exists $args{last_name}) {
374 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
375 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
376 if ref($args{last_name});
377 $self-&gt;{last_nane} = $args{last_name};
378 }
379
380 return bless $self, $class;
381}
382
383sub last_name {
384 my $self = shift;
385
386 if (@_) {
387 my $value = shift;
388 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
389 . &quot;Validation failed for 'Str' with value $value&quot;
390 if ref($value);
391 $self-&gt;{last_name} = $value;
392 }
393
394 return $self-&gt;{last_name};
395}</code></pre>
396
397</div>
398
399<div class="slide">
400 <h1>Side by side</h1>
401
402 <table class="side-by-side">
403 <tr>
404 <td>
405 <pre><code>package Person;
406use Moose;
407
408has last_name =&gt; (
409 is =&gt; 'rw',
410 isa =&gt; 'Str',
411);</code></pre>
412 </td>
413 <td>
414 <pre class="small"><code>package Person;
415use strict;
416use warnings;
417use Carp 'confess';
418
419sub new {
420 my $class = shift;
421 my %args = @_;
422 my $self = {};
423
424 if (exists $args{last_name}) {
425 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
426 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
427 if ref($args{last_name});
428 $self-&gt;{last_nane} = $args{last_name};
429 }
430
431 return bless $self, $class;
432}
433
434sub last_name {
435 my $self = shift;
436
437 if (@_) {
438 my $value = shift;
439 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
440 . &quot;Validation failed for 'Str' with value $value&quot;
441 if ref($value);
442 $self-&gt;{last_name} = $value;
443 }
444
445 return $self-&gt;{last_name};
446}</code></pre>
447 </td>
448 </tr>
449 </table>
450
451</div>
452
453<div class="slide">
454 <h1>Side by side</h1>
455
456 <table class="side-by-side">
457 <tr>
458 <td>
459 <pre><code><span class="match-moose">package Person;</span>
460use Moose;
461
462has last_name =&gt; (
463 is =&gt; 'rw',
464 isa =&gt; 'Str',
465);</code></pre>
466 </td>
467 <td>
468 <pre class="small"><code><span class="match-unsweet">package Person;</span>
469use strict;
470use warnings;
471use Carp 'confess';
472
473sub new {
474 my $class = shift;
475 my %args = @_;
476 my $self = {};
477
478 if (exists $args{last_name}) {
479 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
480 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
481 if ref($args{last_name});
482 $self-&gt;{last_nane} = $args{last_name};
483 }
484
485 return bless $self, $class;
486}
487
488sub last_name {
489 my $self = shift;
490
491 if (@_) {
492 my $value = shift;
493 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
494 . &quot;Validation failed for 'Str' with value $value&quot;
495 if ref($value);
496 $self-&gt;{last_name} = $value;
497 }
498
499 return $self-&gt;{last_name};
500}</code></pre>
501 </td>
502 </tr>
503 </table>
504</div>
505
506<div class="slide">
507 <h1>Side by side</h1>
508
509 <table class="side-by-side">
510 <tr>
511 <td>
512 <pre><code>package Person;
513<span class="match-moose">use Moose;</span>
514
515has last_name =&gt; (
516 is =&gt; 'rw',
517 isa =&gt; 'Str',
518);</code></pre>
519 </td>
520 <td>
521 <pre class="small"><code>package Person;
522<span class="match-unsweet">use strict;
523use warnings;
524use Carp 'confess';
525
526sub new {
527 my $class = shift;
528 my %args = @_;
529 my $self = {};</span>
530
531 if (exists $args{last_name}) {
532 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
533 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
534 if ref($args{last_name});
535 $self-&gt;{last_nane} = $args{last_name};
536 }
537
538 <span class="match-unsweet">return bless $self, $class;
539}</span>
540
541sub last_name {
542 my $self = shift;
543
544 if (@_) {
545 my $value = shift;
546 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
547 . &quot;Validation failed for 'Str' with value $value&quot;
548 if ref($value);
549 $self-&gt;{last_name} = $value;
550 }
551
552 return $self-&gt;{last_name};
553}</code></pre>
554 </td>
555 </tr>
556 </table>
557</div>
558
559<div class="slide">
560 <h1>Side by side</h1>
561
562 <table class="side-by-side">
563 <tr>
564 <td>
565 <pre><code>package Person;
566use Moose;
567
568<span class="match-moose">has last_name =&gt; (</span>
569 is =&gt; 'rw',
570 isa =&gt; 'Str',
571<span class="match-moose">);</span></code></pre>
572 </td>
573 <td>
574 <pre class="small"><code>package Person;
575use strict;
576use warnings;
577use Carp 'confess';
578
579sub new {
580 my $class = shift;
581 my %args = @_;
582 my $self = {};
583
584 <span class="match-unsweet">if (exists $args{last_name}) {</span>
585 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
586 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
587 if ref($args{last_name});
588 <span class="match-unsweet">$self-&gt;{last_nane} = $args{last_name};
589 }</span>
590
591 return bless $self, $class;
592}
593
594sub last_name {
595 my $self = shift;
596
597 if (@_) {
598 my $value = shift;
599 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
600 . &quot;Validation failed for 'Str' with value $value&quot;
601 if ref($value);
602 $self-&gt;{last_name} = $value;
603 }
604
605 return $self-&gt;{last_name};
606}</code></pre>
607 </td>
608 </tr>
609 </table>
610</div>
611
612<div class="slide">
613 <h1>Side by side</h1>
614
615 <table class="side-by-side">
616 <tr>
617 <td>
618 <pre><code>package Person;
619use Moose;
620
621has last_name =&gt; (
622 <span class="match-moose">is =&gt; 'rw',</span>
623 isa =&gt; 'Str',
624);</code></pre>
625 </td>
626 <td>
627 <pre class="small"><code>package Person;
628use strict;
629use warnings;
630use Carp 'confess';
631
632sub new {
633 my $class = shift;
634 my %args = @_;
635 my $self = {};
636
637 if (exists $args{last_name}) {
638 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
639 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
640 if ref($args{last_name});
641 $self-&gt;{last_nane} = $args{last_name};
642 }
643
644 return bless $self, $class;
645}
646
647<span class="match-unsweet">sub last_name {
648 my $self = shift;
649
650 if (@_) {
651 my $value = shift;</span>
652 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
653 . &quot;Validation failed for 'Str' with value $value&quot;
654 if ref($value);
655 <span class="match-unsweet">$self-&gt;{last_name} = $value;
656 }
657
658 return $self-&gt;{last_name};
659}</span></code></pre>
660 </td>
661 </tr>
662 </table>
663</div>
664
665<div class="slide">
666 <h1>Side by side</h1>
667
668 <table class="side-by-side">
669 <tr>
670 <td>
671 <pre><code>package Person;
672use Moose;
673
674has last_name =&gt; (
675 is =&gt; 'rw',
676 <span class="match-moose">isa =&gt; 'Str',</span>
677);</code></pre>
678 </td>
679 <td>
680 <pre class="small"><code>package Person;
681use strict;
682use warnings;
683use Carp 'confess';
684
685sub new {
686 my $class = shift;
687 my %args = @_;
688 my $self = {};
689
690 if (exists $args{last_name}) {
691 <span class="match-unsweet">confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
692 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
693 if ref($args{last_name});</span>
694 $self-&gt;{last_nane} = $args{last_name};
695 }
696
697 return bless $self, $class;
698}
699
700sub last_name {
701 my $self = shift;
702
703 if (@_) {
704 my $value = shift;
705 <span class="match-unsweet">confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
706 . &quot;Validation failed for 'Str' with value $value&quot;
707 if ref($value);</span>
708 $self-&gt;{last_name} = $value;
709 }
710
711 return $self-&gt;{last_name};
712}</code></pre>
713 </td>
714 </tr>
715 </table>
716</div>
717
718<div class="slide">
719 <h1>Side by side</h1>
720
721 <table class="side-by-side">
722 <tr class="incremental">
723 <td>5 lines</td>
724 <td>21 lines</td>
725 </tr>
726 <tr class="incremental">
727 <td>92 characters</td>
728 <td>741 characters</td>
729 </tr>
730 <tr>
731 <td>
732 <pre><code>package Person;
733use Moose;
734
735has last_name =&gt; (
736 is =&gt; 'rw',
737 isa =&gt; 'Str',
738);</code></pre>
739 </td>
740 <td>
741 <pre class="small"><code>package Person;
742use strict;
743use warnings;
744use Carp 'confess';
745
746sub new {
747 my $class = shift;
748 my %args = @_;
749 my $self = {};
750
751 if (exists $args{last_name}) {
752 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
753 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
754 if ref($args{last_name});
755 $self-&gt;{last_nane} = $args{last_name};
756 }
757
758 return bless $self, $class;
759}
760
761sub last_name {
762 my $self = shift;
763
764 if (@_) {
765 my $value = shift;
766 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
767 . &quot;Validation failed for 'Str' with value $value&quot;
768 if ref($value);
769 $self-&gt;{last_name} = $value;
770 }
771
772 return $self-&gt;{last_name};
773}</code></pre>
774 </td>
775 </tr>
776 </table>
777</div>
778
779<div class="slide">
780 <h1>Typo?</h1>
781
782 <pre class="small"><code>sub new {
783 my $class = shift;
784 my %args = @_;
785 my $self = {};
786
787 if (exists $args{last_name}) {
788 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
789 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
790 if ref($args{last_name});
791 $self-&gt;{last_nane} = $args{last_name};
792 }
793
794 return bless $self, $class;
795}</code></pre>
796</div>
797
798<div class="slide">
799 <h1>Typo?</h1>
800
801 <pre class="small"><code>if (exists $args{last_name}) {
802 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
803 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
804 if ref($args{last_name});
805 $self-&gt;{last_nane} = $args{last_name};
806}</code></pre>
807</div>
808
809<div class="slide">
810 <h1>Typo?</h1>
811
812 <code>$self-&gt;{last_nane} = $args{last_name};</code>
813</div>
814
815<div class="slide">
816 <h1>Typo?</h1>
8d1ce1d7 817 <code>$self-&gt;{last_na<span class="wrong">n</span>e}</code>
b751d33f 818</div>
819
820<div class="slide">
821 <h1>Why Moose?</h1>
822
823 <pre><code>package Person;
824use Moose;
825
826has last_name =&gt; (
827 is =&gt; 'rw',
828 isa =&gt; 'Str',
829);</code></pre>
830</div>
831
832<div class="slide fake-slide0">
ba1c9923 833 <h1>Part 1: Moose Classes</h1>
b751d33f 834</div>
835
836<div class="slide">
837 <h1>Moose Classes</h1>
838
839 <ul>
840 <li>Moose classes are Perl packages which <code>use Moose</code></li>
841 </ul>
842</div>
843
844<div class="slide">
845 <h1>Moose.pm and Your Class</h1>
846
847 <pre><code>package Person;
848use Moose;</code></pre>
849
850 <ul>
851 <li><code>Moose.pm</code> provides declarative sugar</li>
9b195048 852 <li>Turns on <code>strict</code> and <code>warnings</code></li>
b751d33f 853 <li>Creates metaclasses for your class: <code>Person-&gt;meta</code></li>
854 <li>Moose classes automatically inherit from <code>Moose::Object</code></li>
855 </ul>
856</div>
857
858<div class="slide">
859 <h1>What <code>Moose::Object</code> Provides</h1>
860
861 <ul>
862 <li>Constructor - <code>new()</code></li>
863 <li>Calls your <code>BUILDARGS()</code> and/or <code>BUILD()</code></li>
864 <li>Calls your <code>DEMOLISH</code> during object destruction</li>
865 </ul>
866</div>
867
868<div class="slide">
d6c8786d 869 <h1>BUILDARGS</h1>
870
871 <ul>
872 <li>Takes <code>@_</code>, returns a hash reference of attribute names/value</li>
873 <li>Accepts a hash or hashref; throws otherwise</li>
874 <li>Provide your own for other cases</li>
875 <li><strong>Always</strong> call <code>$class-&gt;SUPER::BUILDARGS(@_)</code> as a fallback!</li>
876 </ul>
877</div>
878
879<div class="slide">
880 <h1>BUILDARGS Example</h1>
881
882 <pre><code>package Person;
883use Moose;
884
885sub BUILDARGS {
886 my $class = shift;
887
5e2eb691 888 if ( @_ == 1 &amp;&amp; ! ref $_[0] ) {
d6c8786d 889 <span class="highlight">return { ssn =&gt; $_[0] };</span>
890 }
891
892 <span class="highlight">return $class-&gt;SUPER::BUILDARGS(@_)</span>;
893}
894
895<span class="highlight">Person-&gt;new('123-45-6789')</span></code></pre>
896</div>
897
898<div class="slide">
899 <h1>BUILD</h1>
900
901 <ul>
902 <li>Called after object is created, before <code>new</code> returns</li>
903 <li>Chance to do more complex validation, set complex attributes</li>
904 <li>Called in reverse inheritance order, parents to children</li>
905 <li>Return value is ignored</li>
906 </ul>
907</div>
908
909<div class="slide">
910 <h1>BUILD Example</h1>
911
912 <pre><code>package Person;
913use Moose;
914
915sub BUILD {
916 my $self = shift;
917
918 if ( $self-&gt;country_of_residence
919 eq 'USA' ) {
920 die 'All US residents'
921 . ' must have an SSN'
922 unless $self-&gt;has_ssn;
923 }
924}</code></pre>
925</div>
926
927<div class="slide">
7205c6ef 928 <h1>Object Construction a la Moose</h1>
929
930 <pre><code>Person-&gt;new(@_)</code></pre>
931
932 <ol>
933 <li>Calls <code>Person-&gt;BUILDARGS(@_)</code> to turn <code>@_</code> into a hashref</li>
934 <li>Blesses a reference</li>
935 <li>Populates attributes based on the hashref from #1</li>
936 <li>Calls <code>$new_object->BUILDALL($constructor_args)</code>
937 <br />... which calls all <code>BUILD</code> methods</li>
938 <li>Returns the object</li>
939 </ol>
940</div>
941
942<div class="slide">
17d7a564 943 <h1>The Object is Opaque</h1>
7205c6ef 944
945 <ul>
946 <li>Technically it's a hash reference</li>
947 <li><span class="wrong">If you <em>ever</em> treat it as one <strong>you are doing it wrong!</strong></span></li>
948 </ul>
949</div>
950
951<div class="slide">
d6c8786d 952 <h1>DEMOLISH</h1>
953
954 <ul>
955 <li>Like <code>DESTROY</code>, but Moose makes sure all <code>DEMOLISH</code> methods in a hierarchy are called</li>
956 <li>Called in normal inheritance order, children to parents</li>
957 </ul>
958</div>
959
960<div class="slide">
b751d33f 961 <h1>extends</h1>
962
963 <ul>
964 <li><code>extends</code> is sugar for declaring parent classes</li>
965 </ul>
966
967 <pre><code>package Employee;
968use Moose;
969<span class="highlight">extends 'Person';</span></code></pre>
970</div>
971
972<div class="slide">
973 <h1>extends</h1>
974
975 <ul>
976 <li>Each call to <code>extends</code> <strong>resets</strong> your parents</li>
977 </ul>
978
5d572684 979 <h2 class="wrong">Wrong</h2>
b751d33f 980
9b195048 981 <pre><code>package EvilEmployee;
b751d33f 982use Moose;
983extends 'Person';
55906a14 984extends 'Thief';</code></pre>
b751d33f 985
5d572684 986 <h2 class="right">Right</h2>
b751d33f 987
9b195048 988 <pre><code>package EvilEmployee;
b751d33f 989use Moose;
55906a14 990extends 'Person', 'Thief';</code></pre>
b751d33f 991</div>
992
993<div class="slide">
994 <h1>Extending un-Moose-y Parents</h1>
995
996 <pre><code>package My::LWP;
997use Moose;
55906a14 998extends 'LWP';</code></pre>
b751d33f 999
1000 <ul>
1001 <li>No <code>Moose::Object</code>, so ...
1002 <ul>
1003 <li>No attribute-handling <code>new()</code></li>
1004 <li>No <code>BUILDARGS()</code> or <code>BUILD()</code></li>
1005 <li>No <code>DEMOLISH()</code></li>
1006 </ul>
1007 </li>
1008 <li>But see <code>MooseX::NonMoose</code> for a workaround</li>
1009 </ul>
1010</div>
1011
1012<div class="slide">
9fa24ee2 1013 <h1><code>override</code> and <code>super</code></h1>
9b195048 1014
1015 <ul>
9fa24ee2 1016 <li><code>override</code> is another method modifier</li>
9b195048 1017 <li>An alternative to Perl's <code>SUPER::</code></li>
1018 </ul>
1019</div>
1020
1021<div class="slide">
9fa24ee2 1022 <h1><code>override</code> and <code>super</code></h1>
9b195048 1023
1024 <pre><code>package Employee;
1025use Moose;
1026
26164c8d 1027<span class="current incremental">extends 'Person';</span>
9b195048 1028
9fa24ee2 1029<span class="incremental">override</span> work =&gt; sub {
9b195048 1030 my $self = shift;
1031
1032 die "Pay me first" unless $self-&gt;got_paid;
1033 <span class="incremental">super();</span>
1034}<span class="incremental">;</span></code></pre>
55906a14 1035</div>
9b195048 1036
1037<div class="slide">
1038 <h1>Caveat <code>super</code></h1>
1039
1040 <ul>
1041 <li>Mostly like <code>$self-&gt;SUPER::work(@_)</code></li>
1042 <li><strong>But</strong> cannot change <code>@_</code>!</li>
1043 <li>Binds the parent's method at compile time</li>
1044 </ul>
1045</div>
1046
1047<div class="slide">
e43c4c2a 1048 <h1>Minimal Attributes</h1>
9b195048 1049
1050 <ul>
1051 <li><code>has 'foo'</code></li>
1052 <li>Use <code>is =&gt; 'ro'</code> or <code>is =&gt; 'rw'</code></li>
1053 <li>Attributes without "is" have no accessors</li>
1054 </ul>
1055</div>
1056
1057<div class="slide">
1058 <h1>Read-write attributes</h1>
1059
1060 <pre><code>package Person;
1061use Moose;
1062
55906a14 1063has first_name =&gt; ( <span class="highlight">is =&gt; 'rw'</span> );
9b195048 1064
1065my $person =
1066 Person-&gt;new( first_name =&gt; 'Dave' );
1067
1068$person-&gt;first_name('Stevan');
1069print $person-&gt;first_name; # Stevan</code></pre>
1070
1071</div>
1072
1073<div class="slide">
1074 <h1>Read-only attributes</h1>
1075
1076 <pre><code>package Person;
1077use Moose;
1078
55906a14 1079has first_name =&gt; ( <span class="highlight">is =&gt; 'ro'</span> );
9b195048 1080
1081my $person =
1082 Person-&gt;new( first_name =&gt; 'Dave' );
1083
1084$person-&gt;first_name('Stevan');
1085print $person-&gt;first_name; # Dave</code></pre>
1086
1087</div>
1088
1089<div class="slide">
1090 <h1>There is More to Come</h1>
1091
1092 <ul>
1093 <li>Attributes have a <em>lot</em> of features</li>
1094 </ul>
1095</div>
1096
1097<div class="slide">
b751d33f 1098 <h1>Cleaning Up Moose Droppings</h1>
1099
1100 <pre><code>package Person;
1101use Moose;
1102
1103# true
1104Person->can('extends');</code></pre>
1105
1106 <ul>
1107 <li>Not very hygienic</li>
1108 </ul>
1109</div>
1110
1111<div class="slide">
1112 <h1>Cleaning Up Moose Droppings</h1>
1113
1114 <pre><code>package Person;
1115use Moose;
1116
1117...
1118
1119no Moose;
1120
1121# false
1122Person->can('extends');</code></pre>
1123</div>
1124
1125<div class="slide">
1126 <h1>No Moose</h1>
1127
1128 <ul>
1129 <li><code>no Moose</code> at the end of a package is a best practice</li>
17d7a564 1130 <li>Or <code>namespace::clean</code> at the top</li>
b751d33f 1131 <li>Just do it</li>
1132 </ul>
1133</div>
1134
1135<div class="slide">
1136 <h1>Immutability</h1>
1137
1138 <ul>
1139 <li><span style="font-family: URW Chancery L; font-size: 140%">Stevan's Incantation of Fleet-Footedness</span></li>
1140 </ul>
1141
1142 <pre><code>package Person;
1143use Moose;
1144
1145<span class="highlight">__PACKAGE__->meta->make_immutable;</span></code></pre>
1146</div>
1147
9b195048 1148<div class="slide">
1149 <h1>What <code>make_immutable</code> does</h1>
1150
1151 <ul>
1152 <li>Magic</li>
1153 <li>Uses <code>eval</code> to "inline" a constructor</li>
1154 <li>Memoizes a lot of meta-information</li>
1155 <li>Makes loading your class slower</li>
1156 <li>Makes object creation <em>much</em> faster</li>
1157 </ul>
1158</div>
1159
1160<div class="slide">
1161 <h1>When to Immutabilize?</h1>
1162
1163 <ul>
1164 <li><em>Almost</em> always</li>
1165 <li>Startup time vs execution time</li>
1166 </ul>
1167</div>
1168
ddd87d75 1169<div class="slide">
55906a14 1170 <h1>Classes Summary</h1>
1171
1172 <ul>
1173 <li><code>use Moose</code></li>
1174 <li><code>Class-&gt;meta</code></li>
1175 <li><code>Moose::Object</code> base class</li>
9fa24ee2 1176 <li><code>extends</code>, <code>override</code>, and <code>super</code></li>
55906a14 1177 <li>Simple attributes: <code>has</code>, <code>is&nbsp;=&gt;&nbsp;'ro'</code>, &amp; <code>is&nbsp;=&gt;&nbsp;'rw'</code></li>
1178 <li><code>no Moose</code></li>
1179 <li><code>__PACKAGE__-&gt;meta-&gt;make_immutable</code></li>
1180 </ul>
1181</div>
1182
1183<div class="slide">
26164c8d 1184 <h1>Questions?</h1>
1185</div>
1186
1187<div class="slide">
ba1c9923 1188 <h1>Exercises</h1>
ddd87d75 1189
8d1ce1d7 1190 <pre># cd exercises
bcbafd14 1191
4a2daaa5 1192# perl bin/prove -lv t/00-prereq.t
ddd87d75 1193
bcbafd14 1194# perl install-moose (if needed)
ddd87d75 1195
ba1c9923 1196# perl bin/prove -lv t/01-classes.t
1197
ff112bdd 1198# edit lib/Person.pm and lib/Employee.pm
1199
55906a14 1200Iterate til this passes all its tests</pre>
1201</div>
1202
1203<div class="slide fake-slide0">
1204 <h1>Part 2: Roles</h1>
1205</div>
1206
1207<div class="slide">
1208 <h1>Just What Is a Role?</h1>
1209
1210 <ul>
1211 <li>Mixin? Interface? Trait?</li>
1212 <li>Yes ... and more!</li>
1213 </ul>
1214</div>
1215
1216<div class="slide">
1217 <h1>Roles Can Have State <strong>and</strong> Behavior</h1>
1218
1219 <pre><code>package HasPermissions;
1220use Moose::Role;
1221
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
1230 return $self-&gt;access_level &gt;= $required;
1231}</span></code></pre>
1232
1233</div>
1234
1235<div class="slide">
1236 <h1>Roles Can Define Interfaces</h1>
1237
1238 <pre><code>package Printable;
1239use Moose::Role;
1240
1241requires 'as_string';</code></pre>
1242</div>
1243
1244<div class="slide">
1245 <h1>Roles Can Do All Three</h1>
1246
1247 <pre><code>package Printable;
1248use Moose::Role;
1249
1250requires 'as_string';
1251
1252has has_been_printed =&gt; ( is =&gt; 'rw' );
1253
1254sub print {
1255 my $self = shift;
1256 print $self-&gt;as_string;
1257 $self-&gt;has_been_printed(1);
1258}</code></pre>
1259</div>
1260
1261<div class="slide">
1262 <h1>Classes Consume Roles</h1>
1263
1264 <pre><code>package Person;
1265use Moose;
1266
1267with 'HasPermissions';</code></pre>
1268</div>
1269
1270<div class="slide">
1271 <h1>Classes Consume Roles</h1>
1272
1273<pre><code>my $person = Person-&gt;new(
1274 first_name => 'Kenichi',
1275 last_name => 'Asai',
1276 access_level =&gt; 42,
1277);
1278
1279print $person-&gt;full_name
1280 . ' has '
1281 . $person-&gt;can_access(42)
1282 ? 'great power'
1283 : 'little power';</code></pre>
1284</div>
1285
1286<div class="slide">
1287 <h1>Roles in Practice</h1>
1288
1289 <ul>
1290 <li>Consuming a role =~ inlining the role</li>
1291 </ul>
1292</div>
1293
1294<div class="slide">
1295 <h1>In Other Words ...</h1>
1296
1297<pre><code>package Person;
1298use Moose;
1299
1300<span class="highlight">with 'Printable';</span></code></pre>
1301</div>
1302
1303<div class="slide">
1304 <h1>In Other Words ...</h1>
1305
1306<pre><code>package Person;
1307use Moose;
1308
1309<span class="delete">with 'Printable';</span>
1310
1311<span class="highlight">has has_been_printed =&gt; ( is =&gt; 'rw' );
1312
1313sub print {
1314 my $self = shift;
1315 print $self-&gt;as_string;
1316 $self-&gt;has_been_printed(1);
1317}</span></code></pre>
1318</div>
1319
1320<div class="slide">
1321 <h1>Except</h1>
1322
1323 <ul>
1324 <li>Role consumption is introspectable</li>
1325 </ul>
1326
1327 <pre><code>if ( Person-&gt;does('Printable') ) { ... }
1328
1329# or ...
1330
1331if ( Person-&gt;meta-&gt;does('Printable') ) { ... }</code></pre>
1332
1333</div>
1334
1335<div class="slide">
1336 <h1>These Names Are the Same</h1>
1337
1338 <ul>
1339 <li>What if a role and class define the same method?</li>
1340 <li>A class's <em>local</em> methods win over the role's</li>
1341 <li>The role's methods win over the class's <em>inherited</em> methods</li>
1342 </ul>
1343</div>
1344
1345<div class="slide">
1346 <h1>Conflicts Between Roles</h1>
1347
1348 <ul>
1349 <li>Two roles with a method of the same name</li>
1350 <li>Generates a compile-time error when consumed by a class</li>
1351 </ul>
1352</div>
1353
1354<div class="slide">
1355 <h1>Conflict Example</h1>
1356
1357 <pre><code>package IsFragile;
1358use Moose::Role;
1359
1360sub break { ... }
1361
1362package CanBreakdance;
1363use Moose::Role;
1364
1365sub break { ... }</code></pre>
1366</div>
1367
1368<div class="slide">
1369 <h1>Conflict Example</h1>
1370
1371 <pre><code>package FragileDancer;
1372use Moose;
1373
1374<span class="highlight">with 'IsFragile', 'CanBreakdance';</span></code></pre>
1375
1376 <ul>
1377 <li>Only one <code>with</code>!</li>
1378 </ul>
1379</div>
1380
1381<div class="slide">
1382 <h1>Conflict Resolution</h1>
1383
1384 <ul>
0412f089 1385 <li>The consuming class must resolve the conflict by implementing the method</li>
55906a14 1386 <li>Can use some combination of method exclusion and aliasing</li>
1387 </ul>
1388</div>
1389
1390<div class="slide">
1391 <h1>Method Aliasing</h1>
1392
1393 <pre><code>package FragileDancer;
1394use Moose;
1395
1396<span class="highlight">with 'IsFragile' =>
1397 { alias =>
1398 { break => 'break_bone' } },
1399 'CanBreakdance' =>
1400 { alias =>
1401 { break => 'break_it_down' } };</span></code></pre>
1402
1403 <ul>
1404 <li>Renames the roles' methods</li>
1405 <li>Still conflicts, need to <code>exclude</code> as well</li>
1406 </ul>
1407</div>
1408
1409<div class="slide">
1410 <h1>Method Exclusion</h1>
1411
1412 <pre><code>package FragileDancer;
1413use Moose;
1414
1415<span class="highlight">with 'IsFragile' =>
1416 { alias =>
1417 { break => 'break_bone' },
1418 exclude => 'break' },
1419 'CanBreakdance' =>
1420 { alias =>
1421 { break => 'break_dance' },
1422 exclude => 'break' };</span></code></pre>
1423</div>
1424
1425<div class="slide">
1426 <h1>And then ...</h1>
1427
1428 <pre><code>package FragileDancer;
1429use Moose;
ddd87d75 1430
55906a14 1431sub break {
1432 my $self = shift;
1433
1434 $self->break_dance;
232c184d 1435 if ( rand(1) &lt; 0.5 ) {
55906a14 1436 $self->break_bone;
1437 }
1438}</code></pre>
1439</div>
1440
1441<div class="slide">
1442 <h1>Still Full of Fail</h1>
1443
1444 <ul>
1445 <li>Roles are also about semantics!</li>
1446 <li>We've fulfilled the letter and lost the spirit</li>
1447 <li>Roles have a <em>meaning</em></li>
1448 <li>Think twice before blindly aliasing and excluding methods!</li>
1449 </ul>
1450</div>
1451
1452<div class="slide">
1453 <h1>Hot Role-on-Role Action</h1>
1454
1455 <pre><code>package Comparable;
1456use Moose::Role;
1457
1458requires 'compare';</code></pre>
1459</div>
1460
1461<div class="slide">
1462 <h1>Hot Role-on-Role Action</h1>
1463
1464 <pre><code>package TestsEquality;
1465use Moose::Role;
1466
1467with 'Comparable';
1468
1469sub is_equal {
1470 my $self = shift;
1471 return $self->compare(@_) == 0;
1472}</code></pre>
1473</div>
1474
1475<div class="slide">
1476 <h1>And then ...</h1>
1477
1478 <pre><code>package Integer;
1479use Moose;
1480
1481with 'TestsEquality';
1482
1483# Satisfies the Comparable role
1484sub compare { ... }
1485
1486Integer->does('TestsEquality'); # true
1487Integer->does('Comparable'); # also true!</code></pre>
1488</div>
1489
1490<div class="slide">
1491 <h1>Name Conflicts Between Roles</h1>
1492
1493 <pre><code>package HasSubProcess;
1494use Moose::Role;
1495
1496<span class="highlight">sub execute { ... }</span>
1497
1498package Killer;
1499use Moose::Role;
1500
1501with 'HasSubProcess';
1502
1503<span class="highlight">sub execute { ... }</span></code></pre>
1504</div>
1505
1506<div class="slide">
1507 <h1>Delayed Conflict</h1>
1508
1509 <pre><code>package StateOfTexas;
1510with 'Killer';</code></pre>
1511
1512 <ul>
1513 <li><code>StateOfTexas</code> must implement its own <code>execute</code></li>
1514 <li>But loading the <code>Killer</code> role by itself does not cause an error</li>
1515 </ul>
1516</div>
1517
1518<div class="slide">
1519 <h1>Roles as Interfaces</h1>
1520
1521 <ul>
1522 <li>Roles can <code>require</code> methods of their consumers</li>
1523 <li>Compile-time checks</li>
1524 <li>Method must exist when the role is consumed</li>
1525 </ul>
1526</div>
1527
1528<div class="slide">
1529 <h1>The Attribute Gotcha</h1>
1530
1531<pre><code>package HasSize;
1532use Moose::Role;
1533
26164c8d 1534<span class="current incremental">requires 'size';</span>
55906a14 1535
1536package Shirt;
1537use Moose;
1538
1539<span class="incremental">with 'HasSize';
1540
1541has size => ( is => 'ro' );</span></code></pre>
1542</div>
1543
1544<div class="slide">
1545 <h1>The Attribute Gotcha Workaround</h1>
1546
1547 <pre><code>package HasSize;
1548use Moose::Role;
1549
1550requires 'size';
1551
1552package Shirt;
1553use Moose;
1554
1555has size => ( is => 'ro' );
1556
1557with 'HasSize';</code></pre>
1558</div>
1559
1560<div class="slide">
1561 <h1>Compile-time Is a Lie</h1>
1562
1563 <ul>
1564 <li>Really, it's <em>package load</em> time</li>
1565 <li>That's run-time, but before the "real" run-time</li>
1566 <li>Moose does not rewire Perl, it's just sugar!</li>
1567 <li>(but <code>MooseX::Declare</code> <em>does</em> rewire Perl)</li>
1568 </ul>
1569</div>
1570
1571<div class="slide">
1572 <h1>Enforcing Roles</h1>
1573
1574 <pre><code>package Comparison;
1575use Moose;
1576
1577has [ 'left', 'right' ] => (
1578 is => 'ro',
1579 <span class="highlight">does => 'Comparable',</span>
1580);
1581</code></pre>
1582
1583 <ul>
1584 <li>A sneak peek at type constraints</li>
1585 </ul>
1586</div>
1587
1588
1589<div class="slide">
1590 <h1>Roles Can Be Applied to Objects</h1>
1591
1592 <pre><code>use Moose::Util qw( apply_all_roles );
1593
1594my $fragile_person = Person->new( ... );
1595apply_all_roles( $fragile_person, 'IsFragile' );</code></pre>
1596
1597 <ul>
1598 <li>Does not change the <code>Person</code> class</li>
1599 <li>Works with non-Moose classes, great for monkey-patching!</li>
1600 </ul>
1601</div>
1602
1603<div class="slide">
1604 <h1>Roles Are Dirty Too</h1>
1605
1606 <ul>
1607 <li>Once again, clean up those Moose droppings</li>
1608 </ul>
1609
1610 <pre><code>package Comparable;
1611use Moose::Role;
1612
1613requires 'compare';
1614
1615<span class="highlight">no Moose::Role;</span></code></pre>
1616
1617 <ul>
1618 <li>But roles cannot be made immutable</li>
1619 </ul>
1620</div>
1621
1622<div class="slide">
1623 <h1>The Zen of Roles</h1>
1624
1625 <ul>
1626 <li>Roles represent discrete units of ...
1627 <ul>
1628 <li>state</li>
1629 <li>behavior</li>
1630 <li>interface</li>
1631 </ul>
1632 </li>
1633 <li>Roles are shareable between unrelated classes</li>
1634 <li>Roles are what a class <em>does</em>, not what it <em>is</em></li>
1635 <li>Roles <em>add</em> functionality, inheritance <em>specializes</em></li>
1636 </ul>
1637</div>
1638
1639<div class="slide">
1640 <h1>Abstract Examples</h1>
1641
1642 <ul>
1643 <li>Human <em>@ISA</em> Animal</li>
1644 <li>Human <em>does</em> Toolmaker (as <em>does</em> Chimpanzee)</li>
1645 <li>Car <em>@ISA</em> Vehicle</li>
1646 <li>Car <em>does</em> HasEngine</li>
1647 </ul>
1648</div>
1649
1650<div class="slide">
1651 <h1>Real Examples</h1>
1652
1653 <ul>
1654 <li>Objects representing SQL database components and queries
1655 <ul>
1656 <li>Schema, Table, Column, ColumnAlias</li>
1657 <li>Select, Insert, Update, Delete</li>
1658 </ul>
1659 </li>
1660 </ul>
1661</div>
1662
1663<div class="slide">
1664 <h1>Real Examples</h1>
1665
1666 <ul>
1667 <li>Column and ColumnAlias both <em>do</em> ColumnLike</li>
1668 <li>ColumnLike things can be used in certain parts of queries</li>
1669 <li>All queries <em>do</em> HasWhereClause</li>
1670 <li>Select <em>does</em> Comparable and Selectable (for subselects)</li>
1671 <li>A where clause requires its components to <em>do</em> Comparable</li>
1672 </ul>
1673</div>
1674
1675<div class="slide">
26164c8d 1676 <h1>Roles Summary</h1>
1677
1678 <ul>
1679 <li>Roles can define an interface with <code>requires</code></li>
1680 <li>Roles can have state (attributes) and behavior (methods)</li>
1681 <li>Roles can mix interface, state, &amp; behavior</li>
1682 <li>Roles are composed (flattened) into classes</li>
1683 <li>Roles can do other roles</li>
1684 <li>Roles can be used as a type in APIs (must do Comparable)</li>
1685 </ul>
1686</div>
1687
1688<div class="slide">
1689 <h1>Questions?</h1>
1690</div>
1691
1692<div class="slide">
55906a14 1693 <h1>Exercises</h1>
1694
8d1ce1d7 1695 <pre># cd exercises
55906a14 1696# perl bin/prove -lv t/02-roles.t
1697
1698Iterate til this passes all its tests</pre>
1699</div>
1700
8d1ce1d7 1701<div class="slide fake-slide0">
1702 <h1>Part 3: Basic Attributes</h1>
1703</div>
1704
1705<div class="slide">
1706 <h1>Attributes Are Huge</h1>
1707
1708 <ul>
1709 <li>Moose's biggest feature</li>
1710 <li>The target of <em>many</em> MooseX modules</li>
1711 </ul>
1712</div>
1713
1714<div class="slide">
1715 <h1>Quick Review</h1>
1716
1717 <ul>
1718 <li>Declared with <code>has</code></li>
1719 <li>Read-only or read-write</li>
1720 </ul>
1721
1722 <pre><code>package Shirt;
1723use Moose;
1724
1725has 'color' =&gt; ( is =&gt; 'ro' );
1726has 'is_ripped' =&gt; ( is =&gt; 'rw' );</code></pre>
1727</div>
1728
1729<div class="slide">
1730 <h1>Required-ness</h1>
1731
1732 <ul>
1733 <li>Required means "must be passed to the constructor"</li>
1734 <li>But can be <code>undef</code></li>
1735 </ul>
1736</div>
1737
1738<div class="slide">
1739 <h1>Required-ness</h1>
1740
1741 <pre><code>package Person;
1742use Moose;
1743
1744has first_name =&gt; (
1745 is =&gt; 'ro',
26164c8d 1746 <span class="current incremental">required =&gt; 1,</span>
8d1ce1d7 1747);
1748
1749<span class="incremental">Person->new( first_name =&gt; undef ); # ok
1750Person->new(); # kaboom</span></code></pre>
1751</div>
1752
1753<div class="slide">
1754 <h1>Default and Builder</h1>
1755
1756 <ul>
1757 <li>Attributes can have defaults</li>
1758 <li>Simple non-referecne scalars (number, string)</li>
1759 <li>Subroutine reference</li>
1760 <li>A builder method</li>
1761 </ul>
1762</div>
1763
1764<div class="slide">
1765 <h1>Default</h1>
1766
1767 <ul>
1768 <li>Can be a non-reference scalar (including <code>undef</code>)</li>
1769 </ul>
1770
1771 <pre><code>package Person;
1772use Moose;
1773
1774has bank =&gt; (
1775 is =&gt; 'rw',
1776 default =&gt; 'Spire FCU',
1777);</code></pre>
1778</div>
1779
1780<div class="slide">
1781 <h1>Default</h1>
1782
1783 <ul>
1784 <li>Can be a subroutine reference</li>
1785 </ul>
1786
1787 <pre><code>package Person;
1788use Moose;
1789
1790has bank =&gt; (
1791 is =&gt; 'rw',
1792 default =&gt;
1793 sub { Bank-&gt;new(
1794 name =&gt; 'Spire FCU' ) },
1795);</code></pre>
1796</div>
1797
1798<div class="slide">
1799 <h1>Default as a Subroutine Reference</h1>
1800
1801 <ul>
1802 <li>Called as a method on the object</li>
1803 <li>Called anew for each object</li>
1804 </ul>
1805</div>
1806
1807<div class="slide">
1808 <h1>Why No Other Reference Types?</h1>
1809
1810 <pre><code>package Person;
1811use Moose;
1812
1813has bank =&gt; (
1814 is =&gt; 'rw',
1815 <span class="wrong">default =&gt; Bank-&gt;new(
1816 name =&gt; 'Spire FCU' ),</span>
1817);</code></pre>
1818
1819 <ul>
1820 <li>Now <strong>every</strong> person shares the <strong>same</strong> Bank object!</li>
1821 </ul>
1822</div>
1823
1824<div class="slide">
1825 <h1>Defaulting to an Empty Reference</h1>
1826
1827 <pre><code>package Person;
1828use Moose;
1829
1830has packages =&gt; (
1831 is =&gt; 'rw',
1832 default =&gt; <span class="highlight">sub { [] }</span>,
1833);</code></pre>
1834</div>
1835
1836<div class="slide">
1837 <h1>What if I Want to Share?</h1>
1838
1839 <pre><code>package Person;
1840use Moose;
1841
1842my $highlander_bank =
1843 Bank-&gt;new( name =&gt; 'Spire FCU' );
1844
1845has bank =&gt; (
1846 is =&gt; 'rw',
1847 default =&gt; sub { $highlander_bank },
1848);</code></pre>
1849</div>
1850
1851<div class="slide">
1852 <h1>Builder</h1>
1853
1854 <ul>
1855 <li>A method <em>name</em> which returns the default</li>
1856 </ul>
1857</div>
1858
1859<div class="slide">
1860 <h1>Builder</h1>
1861
1862 <pre><code>package Person;
1863use Moose;
1864
1865has bank =&gt; (
1866 is =&gt; 'rw',
1867 builder =&gt; '_build_bank',
1868);
1869
1870sub _build_bank {
1871 my $self = shift;
1872 return Bank-&gt;new( name => 'Spire FCU' );
1873}</code></pre>
1874</div>
1875
1876<div class="slide">
1877 <h1>Default vs Builder</h1>
1878
1879 <ul>
1880 <li>Use default for simple scalars</li>
1881 <li>Use default to return empty references</li>
1882 <li>Use default for <em>very</em> trivial subroutine references</li>
1883 <li>Use builder for everything else</li>
1884 </ul>
1885</div>
1886
1887<div class="slide">
1888 <h1>Builder Bonuses</h1>
1889
1890 <ul>
1891 <li>Can be overridden and method modified, because it's called by <em>name</em></li>
1892 <li>Roles can require a builder</li>
1893 </ul>
1894</div>
1895
1896<div class="slide">
1897 <h1>Role Requires Builder</h1>
1898
1899 <pre><code>package HasBank;
1900use Moose::Role;
1901
1902requires '_build_bank';
1903
1904has bank =&gt; (
1905 is =&gt; 'ro',
1906 builder =&gt; '_build_bank',
1907);</code></pre>
1908</div>
1909
1910<div class="slide">
1911 <h1>Lazy, Good for Nothing Attributes</h1>
1912
1913 <ul>
1914 <li>Normally, defaults are generated during object construction</li>
1915 <li>This can be expensive</li>
1916 <li>We want to default to <code>$self-&gt;size * 2</code>, but attribute initialization order is unpredictable</li>
1917 <li>Use lazy attributes!</li>
1918 </ul>
1919</div>
1920
1921<div class="slide">
1922 <h1>The Power of Dynamic Defaults</h1>
1923
1924 <pre><code>package Person;
1925use Moose;
1926
1927has shoe_size =&gt; (
1928 is =&gt; 'ro',
1929);</code></pre>
1930</div>
1931
1932<div class="slide">
1933 <h1>The Power of Dynamic Defaults</h1>
1934
1935 <pre><code>has shoes =&gt; (
1936 is =&gt; 'ro',
1937 <span class="highlight">lazy =&gt; 1,</span>
1938 builder => '_build_shoes',
1939);
1940
1941sub _build_shoes {
1942 my $self = shift;
1943
1944 return Shoes-&gt;new(
13cb03c7 1945 size =&gt; <span class="highlight">$self-&gt;shoe_size</span> );
8d1ce1d7 1946}</code></pre>
1947</div>
1948
1949<div class="slide">
1950 <h1>Lazy is Good</h1>
1951
1952 <ul>
1953 <li>Lazy defaults are executed when the attribute is read</li>
1954 <li>Can see other object attributes</li>
1955 <li>Still need to watch out for circular laziness</li>
1956 </ul>
1957</div>
1958
1959<div class="slide">
1960 <h1>Clearer and Predicate</h1>
1961
1962 <ul>
1963 <li>Attributes can have a value, including <code>undef</code>, or not</li>
1964 <li>Can clear the value with a clearer method</li>
1965 <li>Can check for the existence of a value with a predicate method</li>
1966 <li>By default, these methods are not created</li>
1967 </ul>
1968</div>
1969
1970<div class="slide">
1971 <h1>Clearer and Predicate</h1>
1972
1973 <pre><code>package Person;
1974use Moose;
1975
1976has account =&gt; (
1977 is =&gt; 'ro',
1978 lazy =&gt; 1,
1979 builder =&gt; '_build_account',
1980 <span class="highlight">clearer =&gt; '_clear_account',
1981 predicate =&gt; 'has_account',</span>
1982);</code></pre>
1983</div>
1984
1985<div class="slide">
1986 <h1>Clearer and Lazy Defaults</h1>
1987
1988 <ul>
1989 <li>Lazy defaults are good for computed attributes</li>
1990 <li>Clear the attribute when the source data changes</li>
1991 <li>Recalculated at next access</li>
1992 </ul>
1993</div>
1994
1995<div class="slide">
1996 <h1>Renaming constructor arguments</h1>
1997
1998 <ul>
1999 <li>By default, constructor names = attribute names</li>
2000 <li>Use <code>init_arg</code> to change this</li>
2001 <li>Set <code>init_arg =&gt; undef</code> to make it unconstructable</li>
2002 </ul>
2003</div>
2004
2005<div class="slide">
2006 <h1>Some <code>init_arg</code> examples</h1>
2007
2008 <pre><code>package Person;
2009use Moose;
2010
2011has shoe_size => (
2012 is =&gt; 'ro',
2013 <span class="highlight">init_arg =&gt; 'foot_size',</span>
2014);
2015
2016Person->new( <span class="wrong">shoe_size =&gt; 13</span> );
2017
2018my $person =
2019 Person->new( <span class="right">foot_size =&gt; 13</span> );
2020print $person->shoe_size;</code></pre>
2021</div>
2022
2023<div class="slide">
2024 <h1>Some <code>init_arg</code> examples</h1>
2025
2026<pre><code>package Person;
2027use Moose;
2028
2029has shoes => (
2030 is =&gt; 'ro',
2031 <span class="highlight">init_arg =&gt; undef,</span>
2032);
2033
2034Person->new( <span class="wrong">shoes =&gt; Shoes-&gt;new</span> );</code></pre>
2035</div>
2036
2037<div class="slide">
2038 <h1>Why Set <code>init_arg =&gt; undef</code>?</h1>
2039
2040 <ul>
2041 <li>Use this with a lazy default for attributes-as-cache</li>
2042 <li>Compute the value as needed</li>
2043 <li>Ensure that it is always generated correctly (not set by constructor)</li>
2044 <li>Use triggers or method modifiers (coming soon) to clear the value</li>
2045 </ul>
2046</div>
2047
2048<div class="slide">
2049 <h1>Attribute Inheritance</h1>
2050
2051 <ul>
2052 <li>By default, subclasses inherit attribute as-is</li>
2053 <li>Can change some attribute parameters in subclasses
2054 <ul>
2055 <li>default</li>
2056 <li>builder</li>
2057 <li>required</li>
2058 <li>lazy</li>
2059 <li>others we've not yet covered</li>
2060 </ul>
2061 </li>
2062 </ul>
2063</div>
2064
2065<div class="slide">
2066 <h1>Attribute Inheritance Example</h1>
2067
2068 <pre><code>package Employee;
2069use Moose;
2070
2071extends 'Person';
2072
2073has '<span class="highlight">+first_name</span>' =&gt; (
2074 default =&gt; 'Joe',
2075);</code></pre>
2076</div>
2077
2078<div class="slide">
2079 <h1>Attribute Inheritance Warning</h1>
2080
2081 <ul>
2082 <li>An attribute is a contract about a class's API</li>
2083 <li>Don't break that contract in a subclass</li>
2084 <li>Especially important in the context of types</li>
2085 </ul>
2086</div>
2087
2088<div class="slide">
2089 <h1>Changing Accessor Names</h1>
2090
2091 <pre><code>package Person;
2092use Moose;
2093
2094has first_name =&gt; (
bd857054 2095 <span class="highlight">accessor</span> =&gt; 'first_name',
8d1ce1d7 2096);</code></pre>
2097
2098 <ul>
2099 <li>The long-hand version of <code>is =&gt; 'rw'</code></li>
2100 </ul>
2101</div>
2102
2103<div class="slide">
2104 <h1>Changing Accessor Names</h1>
2105
2106 <pre><code>package Person;
2107use Moose;
2108
2109has first_name =&gt; (
2110 <span class="highlight">reader</span> =&gt; 'first_name',
2111 <span class="highlight">writer</span> =&gt; undef,
2112);</code></pre>
2113
2114 <ul>
2115 <li>The long-hand version of <code>is =&gt; 'ro'</code></li>
2116 </ul>
2117</div>
2118
2119
2120<div class="slide">
2121 <h1>Changing Accessor Names</h1>
2122
2123 <pre><code>package Person;
2124use Moose;
2125
2126has first_name =&gt; (
2127 <span class="highlight">reader</span> =&gt; 'get_first_name',
de668480 2128 <span class="highlight">writer</span> =&gt; 'set_first_name',
8d1ce1d7 2129);</code></pre>
2130</div>
2131
2132<div class="slide">
2133 <h1>Changing Accessor Names</h1>
2134
2135 <pre><code>package Person;
2136use Moose;
2137
2138has first_name =&gt; (
2139 <span class="highlight">is</span> =&gt; 'rw',
2140 <span class="highlight">writer</span> =&gt; '_first_name',
2141);</code></pre>
2142
2143 <ul>
be6689d2 2144 <li>Can also mix-and-match <code>is</code> and explicit names</li>
8d1ce1d7 2145 </ul>
2146</div>
2147
2148<div class="slide">
2149 <h1>ETOOMUCHTYPING</h1>
2150
2151 <ul>
2152 <li><code>MooseX::FollowPBP</code><br /><code>get_foo</code> and <code>set_foo</code></li>
2153 <li><code>MooseX::SemiAffordanceAccessor</code><br /><code>foo</code> and <code>set_foo</code></li>
2154 </ul>
2155</div>
2156
2157<div class="slide">
2158 <h1>ETOOMUCHTYPING</h1>
2159
2160 <pre><code>package Person;
2161use Moose;
2162<span class="highlight">use MooseX::SemiAffordanceAccessor;</span>
2163
2164has first_name =&gt; (
2165 is =&gt; 'rw',
2166);</code></pre>
2167
2168 <ul>
2169 <li>Creates <code>first_name</code> and <code>set_first_name</code></li>
2170 </ul>
2171</div>
2172
2173<div class="slide">
26164c8d 2174 <h1>Basic Attributes Summary</h1>
2175
2176 <ul>
2177 <li>Attributes can be <code>required</code></li>
2178 <li>Attributes can have a <code>default</code> or <code>builder</code></li>
2179 <li>Attributes with a default or builder can be <code>lazy</code></li>
2180 <li>Attributes can have a <code>clearer</code> and/or <code>predicate</code></li>
2181 <li>An attribute's constructor name can be changed with <code>init_arg</code></li>
2182 <li>A subclass can alter its parents' attributes</li>
2183 <li>Attribute accessor names can be changed</li>
2184 </ul>
2185</div>
2186
2187<div class="slide">
2188 <h1>Questions?</h1>
2189</div>
2190
2191<div class="slide">
8d1ce1d7 2192 <h1>Exercises</h1>
2193
2194 <pre># cd exercises
2195# perl bin/prove -lv t/03-basic-attributes.t
2196
2197Iterate til this passes all its tests</pre>
2198</div>
2199
26164c8d 2200<div class="slide fake-slide0">
2201 <h1>Part 4: Method Modifiers</h1>
2202</div>
2203
2204<div class="slide">
2205 <h1>What is a Method Modifier</h1>
2206
2207 <ul>
2208 <li>Apply to an existing method</li>
2209 <li>... from a parent class, the current class, or a role</li>
2210 <li>Roles can provide modifiers that are applied at composition time</li>
2211 </ul>
2212</div>
2213
2214<div class="slide">
2215 <h1>What is a Method Modifier</h1>
2216
2217 <ul>
0a0c7e7c 2218 <li>"Inject" behavior</li>
26164c8d 2219 <li>Add behavior to generated methods (accessors, delegations)</li>
2220 <li>Provide roles which modify existing behavior</li>
2221 </ul>
2222</div>
2223
2224<div class="slide">
2225 <h1>Before and After</h1>
2226
2227 <ul>
2228 <li>Simplest modifiers - <code>before</code> and <code>after</code></li>
2229 <li>Guess when they run!</li>
2230 </ul>
2231</div>
2232
2233<div class="slide">
2234 <h1>Uses for <code>before</code></h1>
2235
2236 <ul>
2237 <li>As a pre-call check</li>
2238 </ul>
2239
2240 <pre><code>package Person;
2241use Moose;
2242
2243before work =&gt; sub {
2244 my $self = shift;
2245 die 'I have no job!'
2246 unless $self-&gt;has_title;
2247};</code></pre>
2248</div>
2249
2250<div class="slide">
2251 <h1>Uses for <code>before</code></h1>
2252
2253 <ul>
2254 <li>Logging/Debugging</li>
2255 </ul>
2256
2257 <pre><code>package Person;
2258use Moose;
2259
2260before work =&gt; sub {
2261 my $self = shift;
2262 return unless $DEBUG;
2263
2264 warn "Called work on ", $self->full_name,
2265 "with the arguments: [@_]\n";
2266};</code></pre>
2267</div>
2268
2269<div class="slide">
2270 <h1>Uses for <code>after</code></h1>
2271
2272 <ul>
2273 <li>Also works for logging/debugging</li>
2274 <li>Post-X side-effects (recording audit info)</li>
2275 </ul>
2276
2277 <pre><code>package Person;
2278use Moose;
2279
2280after work =&gt; sub {
2281 my $self = shift;
2282 $self-&gt;work_count(
2283 $self-&gt;work_count + 1 );
2284};</code></pre>
2285</div>
2286
2287<div class="slide">
2288 <h1>Other Uses</h1>
2289
2290 <ul>
2291 <li>Modifiers are useful for adding behavior to generated methods</li>
2292 </ul>
2293</div>
2294
2295<div class="slide">
2296 <h1>Other Uses Example</h1>
2297
2298 <pre><code>has password =&gt; (
2299 is =&gt; 'rw',
2300 clearer =&gt; 'clear_password',
2301);
2302
2303has hashed_password =&gt; (
2304 is =&gt; 'ro',
2305 builder =&gt; '_build_hashed_password',
2306 clearer =&gt; '_clear_hashed_password',
2307);
2308
2309after clear_password =&gt; sub {
2310 my $self = shift;
2311 $self-&gt;_clear_hashed_password;
2312};</code></pre>
2313</div>
2314
2315<div class="slide">
2316 <h1><code>before</code> and <code>after</code> Limitations</h1>
2317
2318 <ul>
2319 <li>Cannot alter method parameters</li>
2320 <li>Cannot alter return value</li>
2321 <li>But <strong>can</strong> throw an exception</li>
2322 </ul>
2323</div>
2324
2325<div class="slide">
2326 <h1>The <code>around</code> Modifier</h1>
2327
2328 <ul>
2329 <li>The big gun</li>
2330 <li>Can alter parameters <strong>and/or</strong> return values</li>
2331 <li>Can skip calling the wrapped method entirely</li>
2332 </ul>
2333</div>
2334
2335<div class="slide">
2336 <h1>The power of <code>around</code></h1>
2337
2338 <pre><code>around insert =&gt; sub {
2339 my $orig = shift;
2340 my $self = shift;
2341
2342 $self-&gt;_validate_insert(@_);
2343
2344 my $new_user =
2345 $self-&gt;$orig(
2346 $self-&gt;_munge_insert(@_) );
2347
2348 $new_user->_assign_uri;
2349
2350 return $new_user;
2351};</code></pre>
2352</div>
2353
2354<div class="slide">
2355 <h1>Modifier Order</h1>
2356
2357 <ul>
2358 <li>Before runs order from last to first</li>
2359 <li>After runs in order from first to last</li>
2360 <li>Around runs in order from last to first</li>
2361 </ul>
2362</div>
2363
2364<div class="slide">
2365 <h1>Modifier Order Illustrated</h1>
2366
2367<pre>
2368<span class="current incremental">before 2
2369 before 1</span>
2370 <span class="incremental">around 2
2371 around 1</span>
2372 <span class="incremental">wrapped method</span>
2373 <span class="incremental">around 1
2374 around 2</span>
2375 <span class="incremental">after 1
2376after 2</span>
2377</pre>
2378</div>
2379
2380<div class="slide">
2381 <h1>Modifiers in Roles</h1>
2382
2383 <ul>
2384 <li>Roles can use these modifiers</li>
2385 <li>Very powerful!</li>
2386 </ul>
2387</div>
2388
2389<div class="slide">
2390 <h1>Modifiers in Roles</h1>
2391
2392 <pre><code>package IsUnreliable;
2393use Moose::Role;
2394
2395<span class="highlight">requires 'run';
2396
2397around run</span> =&gt; sub {
2398 my $orig = shift;
2399 my $self = shift;
2400
2401 return if rand(1) &lt; 0.5;
2402
2403 return $self-&gt;$orig(@_);
2404};</code></pre>
2405</div>
2406
2407<div class="slide">
2408 <h1>Augment and Inner</h1>
2409
2410 <ul>
2411 <li>Inverted <code>super</code></li>
2412 <li>From least- to most-specific</li>
2413 <li>Grandparent to parent to child</li>
2414 <li>Not allowed in roles</li>
2415 </ul>
2416</div>
2417
2418<div class="slide">
2419 <h1>Augment and Inner</h1>
2420
2421 <pre><code>package Document;
2422
2423sub xml { '&lt;doc&gt;' . <span class="highlight">inner()</span> . '&lt;/doc&gt;' }
2424
2425package Report;
2426extends 'Document';
2427
c3ccfa10 2428<span class="highlight">augment xml</span> =&gt;
2429 sub { title() . <span class="highlight">inner()</span> . summary() };
26164c8d 2430
2431package TPSReport;
2432extends 'Report';
2433
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
2514# perl bin/prove -lv t/04-method-modifiers.t
2515
2516Iterate til this passes all its tests</pre>
2517</div>
2518
5d572684 2519<div class="slide fake-slide0">
2520 <h1>Part 5: Types</h1>
2521</div>
2522
636ceec1 2523<div class="slide">
2524 <h1>A Type System for Perl</h1>
2525
2526 <ul>
2527 <li>Sort of ...</li>
2528 <li><em>Variables</em> are not typed</li>
2529 <li>Attributes can have types</li>
2530 <li>MooseX modules let you define method signatures</li>
2531 </ul>
2532</div>
2533
2534<div class="slide">
2535 <h1>Components of a Moose Type</h1>
2536
2537 <ul>
2538 <li>A type is a name and a constraint</li>
2539 <li>Types have a hierarchy</li>
2540 <li>Constraints are cumulative from parents</li>
2541 <li>Types can have associated coercions</li>
2542 </ul>
2543</div>
2544
2545<div class="slide">
2546 <h1>Built-in Type Hierarchy</h1>
2547
2548 <pre>
2549Any
2550Item
2551 Bool
2552 Maybe[`a]
2553 Undef
2554 Defined
2555 Value
2556 Num
2557 Int
2558 Str
2559 ClassName
2560 RoleName
2561</pre>
2562</div>
2563
2564<div class="slide">
2565 <h1>Built-in Type Hierarchy</h1>
2566
2567<pre>
2568(Item)
2569 (Defined)
2570 Ref
2571 ScalarRef
2572 ArrayRef[`a]
2573 HashRef[`a]
2574 CodeRef
2575 RegexpRef
2576 GlobRef
2577 FileHandle
2578 Object
2579</pre>
2580</div>
2581
2582<div class="slide">
2583 <h1>Bool</h1>
2584
2585 <h2>True</h2>
2586 <pre><code>1
2587924.1
2588'true'
2589{}</code></pre>
2590
2591 <h2>False</h2>
2592 <pre><code>0
25930.0
2594'0'
2595undef</code></pre>
2596
2597 <ul>
2598 <li>Like Perl's <code>if ($foo)</code></li>
2599 </ul>
2600</div>
2601
2602<div class="slide">
2603 <h1>Value (and subtypes)</h1>
2604
2605 <ul>
b59551bc 2606 <li><code>Value</code> is true when <code>! ref $thing</code></li>
2607 <li><code>Value</code> and <code>Str</code> are effectively the same, but <code>Str</code> is more expressive</li>
636ceec1 2608 <li>An overloaded object which numifies does not pass the <code>Num</code> constraint!</li>
2609 <li>Perl 5's overloading is hopelessly broken</li>
2610 </ul>
2611</div>
2612
2613<div class="slide">
2614 <h1>ClassName and RoleName</h1>
2615
2616 <ul>
2617 <li>A string with a package name</li>
2618 <li>The package <strong>must already be loaded</strong></li>
2619 </ul>
2620</div>
2621
2622<div class="slide">
2623 <h1>Parameterizable Types</h1>
2624
2625 <ul>
2626 <li>What does <code>ArrayRef[`a]</code> mean?</li>
2627 <li><code>s/`a/Int/</code> (or <code>Str</code> or ...)</li>
2628 <li>When you use it you can write ...
2629 <ul>
2630 <li><code>ArrayRef</code> (== <code>ArrayRef[Item]</code>)</li>
2631 <li><code>ArrayRef[Str]</code></li>
2632 <li><code>ArrayRef[MyTypeName]</code></li>
2633 <li><code>ArrayRef[HashRef[Maybe[Int]]]</code></li>
2634 </ul>
2635 </li>
2636 </ul>
2637</div>
2638
2639<div class="slide">
2640 <h1>Maybe[`a]</h1>
2641
2642 <ul>
2643 <li>Maybe means either the named type or <code>undef</code></li>
2644 <li><code>Maybe[Int]</code> accepts integers or <code>undef</code></li>
2645 </ul>
2646</div>
2647
2648<div class="slide">
b59551bc 2649 <h1>Type Union</h1>
636ceec1 2650
2651 <ul>
2652 <li>This or that (or that or ...)</li>
2653 <li><code>Int | ArrayRef[Int]</code></li>
2654 <li>But use a coercion instead when possible</li>
b59551bc 2655 <li>Or use a <code>role_type</code>, <code>duck_type</code>, or anything not a union</li>
2656 <li>A union is often a code smell</li>
636ceec1 2657 </ul>
2658</div>
2659
2660<div class="slide">
2661 <h1>Making Your Own Types</h1>
2662
2663 <pre><code>use Moose::Util::TypeConstraints;
2664
2665<span class="incremental current">subtype 'PositiveInt',</span>
2666 <span class="incremental">as 'Int',</span>
2667 <span class="incremental">where { $_ &gt; 0 },</span>
2668 <span class="incremental">message { "The value you provided ($_)"
2669 . " was not a positive number." };</span>
2670
2671has size =&gt; (
2672 is =&gt; 'ro',
2673 <span class="incremental">isa =&gt; 'PositiveInt',</span>
2674);</code></pre>
2675</div>
2676
2677<div class="slide">
2678 <h1>Automatic Types</h1>
2679
2680 <ul>
2681 <li>Moose creates a type for every Moose class and role</li>
2682 <li>Unknown names are assumed to be classes</li>
2683 </ul>
2684</div>
2685
2686<div class="slide">
2687 <h1>Automatic Types</h1>
2688
2689 <pre><code>package Employee;
2690use Moose;
2691
2692has manager =&gt; (
2693 is =&gt; 'rw',
2694 <span class="highlight">isa =&gt; 'Employee',</span>
2695);
2696
2697has start_date =&gt; (
2698 is =&gt; 'ro',
2699 <span class="highlight">isa =&gt; 'DateTime',</span>
2700);</code></pre>
2701</div>
2702
2703<div class="slide">
2704 <h1>Subtype Shortcuts - <code>class_type</code></h1>
2705
2706 <pre><code>use Moose::Util::TypeConstraints;
2707class_type 'DateTime';
2708
2709subtype 'DateTime',
2710 as 'Object',
2711 where { $_-&gt;isa('DateTime') },
2712 message { ... };</code></pre>
2713</div>
2714
2715<div class="slide">
2716 <h1>Subtype Shortcuts - <code>role_type</code></h1>
2717
2718 <pre><code>use Moose::Util::TypeConstraints;
2719role_type 'Printable';
2720
2721subtype 'Printable',
2722 as 'Object',
2723 where
2724 { Moose::Util::does_role(
2725 $_, 'Printable' ) },
2726 message { ... };</code></pre>
2727</div>
2728
2729<div class="slide">
2730 <h1>Subtype Shortcuts - <code>duck_type</code></h1>
2731
2732 <pre><code>use Moose::Util::TypeConstraints;
2733duck_type Car =&gt; qw( run break_down );
2734
2735subtype 'Car',
2736 as 'Object',
2737 where { all { $_-&gt;can($_) }
2738 qw( run break_down ) },
2739 message { ... };</code></pre>
2740</div>
2741
2742<div class="slide">
2743 <h1>Subtype Shortcuts - <code>enum</code></h1>
2744
2745 <pre><code>use Moose::Util::TypeConstraints;
2746enum Color =&gt; qw( red blue green ) );
2747
2748my %ok = map { $_ =&gt; 1 } qw( red blue green );
2749subtype 'Color'
2750 as 'Str',
2751 where { $ok{$_} },
2752 message { ... };</code></pre>
2753</div>
2754
2755<div class="slide">
2756 <h1>Anonymous Subtypes</h1>
2757
2758 <pre><code>package Person;
2759
2760<span class="highlight">my $posint =
2761 subtype as 'Int', where { $_ &gt; 0 };</span>
2762
2763has size =&gt; (
2764 is =&gt; 'ro',
2765 <span class="highlight">isa =&gt; $posint,</span>
2766);</code></pre>
2767
2768 <ul>
2769 <li>Shortcuts have anonymous forms as well</li>
2770 </ul>
2771</div>
2772
2773<div class="slide">
2774 <h1>Coercions</h1>
2775
2776 <pre><code>use Moose::Util::TypeConstraints;
2777
2778subtype 'UCStr',
2779 as 'Str',
2780 where { ! /[a-z]/ };
2781
2782<span class="incremental current">coerce 'UCStr',</span>
2783 <span class="incremental">from 'Str',</span>
2784 <span class="incremental">via { uc };</span>
2785
2786has shouty_name =&gt; (
2787 is =&gt; 'ro',
2788 isa =&gt; 'UCStr',
2789 <span class="incremental">coerce =&gt; 1,</span>
2790);</code></pre>
2791</div>
2792
2793<div class="slide">
b59551bc 2794 <h1>Coercion Examples</h1>
2795
2796 <pre><code>subtype 'My::DateTime',
2797 as class_type 'DateTime';
2798
2799coerce 'My::DateTime',
2800 from 'HashRef',
2801 via { DateTime-&gt;new( %{$_} ) };
2802
2803coerce 'My::DateTime',
2804 from 'Int',
2805 via { DateTime-&gt;from_epoch(
2806 epoch =&gt; $_ ) };</code></pre>
2807
2808 <ul>
2809 <li>Use coercion to inflate a value</li>
2810 </ul>
2811</div>
2812
2813<div class="slide">
2814 <h1>Coercion Examples</h1>
2815
2816 <pre><code>coerce 'ArrayRef[Int]',
2817 from 'Int',
2818 via { [ $_ ] };</code></pre>
2819
2820 <ul>
2821 <li>Coerce instead of a union like <code style="white-space: nowrap">Int | ArrayRef[Int]</code></li>
2822 </ul>
2823</div>
2824
b59551bc 2825<div class="slide">
2826 <h1>Using Types with Attributes</h1>
2827
2828 <pre><code>package Person;
2829
2830use Moose::Util::TypeConstraints;
2831
2832has height =&gt; (
2833 is =&gt; 'rw',
2834 <span class="highlight">isa =&gt; 'Num',</span>
2835);
2836
2837has favorite_numbers =&gt; (
2838 is =&gt; 'rw',
2839 <span class="highlight">isa =&gt; 'ArrayRef[Int]',
2840 coerce =&gt; 1,</span>
2841);</code></pre>
2842</div>
2843
2844<div class="slide">
ee2e815e 2845 <h1>More Droppings</h1>
2846
2847 <ul>
2848 <li><code>Moose::Util::TypeConstraint</code> also needs cleanup</li>
2849 </ul>
2850
2851 <pre><code>package Person;
2852
2853use Moose;
2854use Moose::Util::TypeConstraints;
2855
2856subtype ...;
2857
2858no Moose;
2859<span class="highlight">no Moose::Util::TypeConstraints;</span></code></pre>
2860</div>
2861
2862<div class="slide">
b59551bc 2863 <h1>Typed Methods (Low-tech)</h1>
2864
2865 <pre class="medium"><code>package Person;
2866<span class="highlight">use MooseX::Params::Validate qw( validated_list );</span>
2867
2868sub work {
2869 my $self = shift;
2870 <span class="highlight">my ( $tasks, $can_rest ) =
2871 validated_list(
2872 \@_,
2873 tasks =&gt;
2874 { isa =&gt; 'ArrayRef[Task]',
2875 coerce =&gt;1 },
2876 can_rest =&gt;
2877 { isa =&gt; 'Bool',
2878 default =&gt; 0 },
2879 );</span>
2880
2881 ...
2882}</code></pre>
68af922f 2883</div>
b59551bc 2884
2885<div class="slide">
2886 <h1>Typed Methods (High-tech)</h1>
2887
2888 <pre class="medium"><code>package Person;
2889
2890<span class="highlight">use MooseX::Method::Signatures;</span>
2891
2892<span class="highlight">method work ( ArrayRef[Task] :$tasks,
2893 Bool :$can_rest = 0 )</span> {
2894 my $self = shift;
2895
2896 ...
2897}</code></pre>
68af922f 2898</div>
b59551bc 2899
2900<div class="slide">
636ceec1 2901 <h1>Digression: The Type Registry</h1>
2902
2903 <ul>
2904 <li>Types are actually <code>Moose::Meta::TypeConstraint</code> <em>objects</em></li>
2905 <li>Stored in an interpreter-global registry mapping names to objects</li>
2906 </ul>
2907</div>
2908
2909<div class="slide">
2910 <h1>Danger!</h1>
2911
2912 <ul>
2913 <li>Coercions are attached to type objects</li>
2914 <li>Therefore also global</li>
2915 <li>Name conflicts between modules!</li>
2916 <li>Coercion conflicts between modules!</li>
2917 </ul>
2918</div>
2919
2920<div class="slide">
b59551bc 2921 <h1>Namespace Fix</h1>
636ceec1 2922
2923 <ul>
2924 <li>Use some sort of pseudo-namespacing scheme</li>
2925 <li>Never coerce directly to a class name, or <em>to</em> built-in types</li>
2926 </ul>
2927</div>
2928
2929<div class="slide">
2930 <h1>Namespace Fix</h1>
2931
2932 <pre><code>use Moose::Util::TypeConstraints;
2933
2934subtype <span class="highlight">'MyApp::Type::DateTime',</span>
2935 as 'DateTime';
2936
2937<span class="highlight">coerce 'MyApp::Type::DateTime',</span>
2938 from 'HashRef',
2939 via { DateTime-&gt;new( %{$_} ) }
2940
2941has creation_date =&gt; (
2942 is =&gt; 'ro',
2943 <span class="highlight">isa =&gt; 'MyApp::Type::DateTime',</span>
2944 coerce =&gt; 1,
2945);</code></pre>
2946</div>
2947
2948<div class="slide">
2949 <h1>Namespace Fix</h1>
2950
2951 <pre><code>subtype 'MyApp::Type::ArrayOfInt',
2952 as 'ArrayRef[Int]';
2953
2954coerce 'MyApp::Type::ArrayOfInt',
2955 from 'Int',
2956 via { [ $_ ] };</code></pre>
2957</div>
636ceec1 2958
2959<div class="slide">
b59551bc 2960 <h1>Namespace Fix Pros and Cons</h1>
636ceec1 2961
b59551bc 2962 <ul>
2963 <li><span class="right">Relatively simple</span></li>
2964 <li><span class="right">Already built into Moose</span></li>
2965 <li><span class="wrong">Conflates type and module namespaces</span></li>
2966 <li><span class="wrong">Type names are strings, so typos are easy to make and may be hard to find</span></li>
2967 </ul>
2968</div>
636ceec1 2969
b59551bc 2970<div class="slide">
2971 <h1>MooseX::Types</h1>
636ceec1 2972
b59551bc 2973 <pre><code>package MyApp::Types;
2974
2975use MooseX::Types
2976 <span class="highlight">-declare =&gt; [ qw( ArrayOfInt ) ]</span>;
2977use MooseX::Types::Moose
2978 qw( ArrayRef Int );
2979
2980subtype <span class="highlight">ArrayOfInt</span>,
2981 as ArrayRef[Int];
2982
2983coerce <span class="highlight">ArrayOfInt</span>
2984 from Int,
2985 via { [ $_ ] };</code></pre>
2986</div>
2987
2988<div class="slide">
2989 <h1>MooseX::Types</h1>
2990
2991 <pre><code>package MyApp::Account;
2992
2993use MyApp::Types qw( ArrayOfInt );
2994
2995has transaction_history => (
2996 is => 'rw',
2997 isa => ArrayOfInt,
2998);</code></pre>
68af922f 2999</div>
b59551bc 3000
3001<div class="slide">
3002 <h1>MooseX::Types</h1>
636ceec1 3003
3004 <ul>
b59551bc 3005 <li>Type names are exported functions, catches typos early</li>
3006 <li>Types must be pre-declared</li>
3007 <li>Types are stored with namespaces internally, but externally are short</li>
3008 <li>Import existing Moose types as functions from <code>MooseX::Types::Moose</code></li>
3009 <li>Still need string names for things like <code>ArrayRef['Email::Address']</code></li>
636ceec1 3010 </ul>
3011</div>
3012
3013<div class="slide">
b59551bc 3014 <h1>MooseX::Types Pros and Cons</h1>
636ceec1 3015
b59551bc 3016 <ul>
3017 <li><span class="right">Catches typos at compile time</span></li>
3018 <li><span class="right">Automatic namespacing</span></li>
3019 <li><span class="wrong">One more thing to install and learn</span></li>
3020 <li><span class="wrong">Every name gets types twice (declared and then defined)</span></li>
3021 <li><span class="wrong">Still stuck with strings when referring to class or role names</span></li>
68af922f 3022 <li><span class="wrong">Coercion gotcha from earlier still applies to types exported from <code>MooseX::Types::Moose</code></span></li>
b59551bc 3023 </ul>
3024</div>
3025
3026<div class="slide">
3027 <h1>Recommendation</h1>
636ceec1 3028
3029 <ul>
b59551bc 3030 <li>Use <code>MooseX::Types</code></li>
3031 <li>Compile time error catching and automatic namespacing are huge wins</li>
3032 <li>Docs from <code>Moose::Util::TypeConstraints</code> are 98% compatible with <code>MooseX::Types</code> anyway</li>
3033 <li>A function exported by a type library works wherever a type name would</li>
636ceec1 3034 </ul>
3035</div>
3036
3037<div class="slide">
3038 <h1>Questions?</h1>
3039</div>
3040
3041<div class="slide">
3042 <h1>Exercises</h1>
3043
3044 <pre># cd exercises
3045# perl bin/prove -lv t/05-types.t
3046
3047Iterate til this passes all its tests</pre>
3048</div>
3049
5d572684 3050<div class="slide fake-slide0">
3051 <h1>Part 6: Advanced Attributes</h1>
3052</div>
3053
3054<div class="slide">
3055 <h1>Weak References</h1>
3056
3057 <ul>
3058 <li>A weak reference lets you avoid circular references</li>
3059 <li>Weak references do not increase the reference count</li>
3060 </ul>
3061</div>
3062
3063<div class="slide">
3064 <h1>Circular Reference Illustrated</h1>
3065
3066 <pre><code>my $foo = {};
3067my $bar = { foo =&gt; $foo };
3068$foo-&gt;{bar} = $bar;</code></pre>
3069
3070 <ul>
3071 <li>Neither <code>$foo</code> nor <code>$bar</code> go out of scope<br />
3072 (until the program exits)</li>
3073 </ul>
3074</div>
3075
3076<div class="slide">
3077 <h1>Weakening Circular References</h1>
3078
3079 <pre><code>use Scalar::Util qw( weaken );
3080
3081my $foo = {};
3082my $bar = { foo =&gt; $foo };
3083$foo-&gt;{bar} = $bar;
3084weaken $foo-&gt;{bar}</code></pre>
3085
3086 <ul>
3087 <li>When <code>$bar</code> goes out of scope, <code>$foo-&gt;{bar}</code> becomes <code>undef</code></li>
3088 </ul>
3089</div>
3090
3091<div class="slide">
3092 <h1>Circular References in Attributes</h1>
3093
3094 <pre><code>package Person;
3095use Moose;
3096
3097has name =&gt; ( is =&gt; 'ro' );
3098has friend =&gt; ( is =&gt; 'rw' );
3099
3100my $alice = Person-&gt;new( name =&gt; 'Alice' );
3101my $bob = Person-&gt;new( name =&gt; 'Bob' );
3102$bob-&gt;friend($alice);
3103$alice-&gt;friend($bob);</code></pre>
3104</div>
3105
3106<div class="slide">
3107 <h1>The Fix</h1>
3108
3109 <pre><code>package Person;
3110use Moose;
3111
3112has name =&gt; ( is =&gt; 'ro' );
3113has friend =&gt; ( is =&gt; 'rw', <span class="highlight">weak_ref =&gt; 1</span> );
3114
3115my $alice = Person-&gt;new( name =&gt; 'Alice' );
3116my $bob = Person-&gt;new( name =&gt; 'Bob' );
3117$bob-&gt;friend($alice);
3118$alice-&gt;friend($bob);</code></pre>
3119</div>
3120
3121<div class="slide">
3122 <h1>Under the Hood</h1>
3123
3124 <ul>
3125 <li>A <code>weak_ref</code> attribute calls <code>weaken</code> ...
3126 <ul>
3127 <li>during object construction</li>
3128 <li>when the attribute is set via a writer</li>
3129 </ul>
3130 </li>
3131 </ul>
3132</div>
3133
3134<div class="slide">
3135 <h1>Triggers</h1>
3136
3137 <ul>
3138 <li>A code reference run after an attribute is <em>set</em></li>
3139 <li>Like an <code>after</code> modifier, but makes intentions clearer</li>
3140 </ul>
3141
3142 <h2 class="wrong">Gross</h2>
3143
3144 <pre><code>after salary_level =&gt; {
3145 my $self = shift;
3146 return unless @_;
3147 $self-&gt;clear_salary;
3148};</code></pre>
3149</div>
3150
3151<div class="slide">
3152 <h1>Use a Trigger Instead</h1>
3153
3154 <h2 class="right">Cleaner</h2>
3155
3156 <pre><code>has salary_level =&gt; (
3157 is =&gt; 'rw',
3158 trigger =&gt; sub { $_[0]-&gt;clear_salary },
3159);</code></pre>
3160</div>
3161
3162<div class="slide">
3163 <h1>Delegation</h1>
3164
3165 <ul>
3166 <li>Attributes can be objects</li>
3167 <li>Delegation transparently calls methods on those objects</li>
3168 </ul>
3169</div>
3170
3171<div class="slide">
3172 <h1>Delegation Examples</h1>
3173
3174 <pre><code>package Person;
3175
3176has lungs =&gt; (
3177 is =&gt; 'ro',
3178 isa => 'Lungs',
3179 <span class="highlight">handles =&gt; [ 'inhale', 'exhale' ],</span>
3180);</code></pre>
3181
3182 <ul>
3183 <li>Creates <code>$person-&gt;inhale</code> and <code>-&gt;exhale</code> methods</li>
3184 <li>Internally calls <code>$person-&gt;lungs-&gt;inhale</code></li>
3185 </ul>
3186</div>
3187
3188<div class="slide">
3189 <h1>Why Delegation?</h1>
3190
3191 <ul>
3192 <li>Reduce the number of classes exposed</li>
3193 <li>Re-arrange class internals -<br />
3194 turn a method into an attribute with delegation</li>
3195 <li>Provide convenenience methods</li>
3196 </ul>
3197</div>
3198
3199<div class="slide">
3200 <h1>Moose's <code>handles</code> Parameter</h1>
3201
3202 <ul>
3203 <li>Accepts many arguments ...
3204 <ul>
3205 <li>Array reference - list of methods to delegate as-is</li>
3206 <li>Hash reference - map of method names</li>
3207 <li>Regex - delegates all matching methods</li>
3208 <li>Role name - delegates all methods in the role</li>
3209 <li>Sub reference - does something complicated ;)</li>
3210 </ul>
3211 </li>
3212 </ul>
3213</div>
3214
3215<div class="slide">
3216 <h1>Array Reference</h1>
3217
3218 <ul>
3219 <li>Takes each method name and creates a simple delegation from the delegating class to the delegatee attribute</li>
3220 </ul>
3221</div>
3222
3223<div class="slide">
3224 <h1>Hash Reference</h1>
3225
3226 <ul>
3227 <li>Mapping of names in the delegating class to the delegatee class</li>
3228 </ul>
3229
3230 <pre><code>package Person;
3231use Moose;
3232
3233has account =&gt; (
3234 is =&gt; 'ro',
3235 isa =&gt; 'BankAccount',
3236 <span class="highlight">handles =&gt; {
3237 receive_money =&gt; 'deposit',
3238 give_money =&gt; 'withdraw',
3239 },</span>
3240);</code></pre>
3241</div>
3242
3243<div class="slide">
3244 <h1>Hash Reference Detailed</h1>
3245
3246 <pre><code> handles =&gt; {
3247 receive_money =&gt; 'deposit',
3248 give_money =&gt; 'withdraw',
3249 },</code></pre>
3250
3251 <ul>
3252 <li><code>$person-&gt;receive_money</code> = <code>$person-&gt;account-&gt;deposit</code></li>
3253 <li><code>$person-&gt;give_money</code> = <code>$person-&gt;account-&gt;withdraw</code></li>
3254 </ul>
3255</div>
3256
3257<div class="slide">
3258 <h1>Regex</h1>
3259
3260 <pre><code>package Person;
3261use Moose;
3262
3263has name =&gt; (
3264 is =&gt; 'ro',
3265 isa =&gt; 'Name',
3266 handles =&gt; qr/.*/,
3267);</code></pre>
3268
3269 <ul>
3270 <li>Creates a delegation for every method in the Name class</li>
3271 <li>Excludes <code>meta</code> and methods inherited from <code>Moose::Object</code></li>
3272 </ul>
3273</div>
3274
3275<div class="slide">
3276 <h1>Role Name</h1>
3277
3278 <pre><code>package Auditor;
3279use Moose::Role;
3280
3281sub record_change { ... }
3282sub change_history { ... }
3283
3284package Account;
3285use Moose;
3286
3287has history =&gt; (
3288 is =&gt; 'ro',
3289 does =&gt; 'Auditor',
3290 <span class="highlight">handles =&gt; 'Auditor',</span>
3291);</code></pre>
3292</div>
3293
3294<div class="slide">
3295 <h1>Role Name Detailed</h1>
3296
3297 <ul>
3298 <li>Account gets delegate methods for each method in the <code>Auditor</code> role
3299 <ul>
3300 <li>record_history</li>
3301 <li>change_history</li>
3302 </ul>
3303 </li>
3304 </ul>
3305</div>
3306
3307<div class="slide">
1c32806a 3308 <h1>Native Delegation</h1>
3309
3310 <ul>
3311 <li>Delegate to <em>unblessed</em> Perl types</li>
3312 <li>Scalar, array or hash ref, etc</li>
3313 </ul>
3314</div>
3315
3316<div class="slide">
3317 <h1>Native Delegation - Array</h1>
3318
3319 <pre><code>package Person;
3320use Moose;
3321
3322has _favorite_numbers =&gt; (
3323 traits =&gt; [ 'Array' ],
3324 is =&gt; 'ro',
3325 isa =&gt; 'ArrayRef[Int]',
3326 default =&gt; sub { [] },
3327 init_arg =&gt; undef,
3328 <span class="highlight">handles =&gt;
3329 { favorite_numbers =&gt; 'elements',
3330 add_favorite_number =&gt; 'push',
3331 },</span>
3332);</code></pre>
3333
3334 <ul>
3335 <li>Automatically defaults to <code>[]</code></li>
3336 </ul>
3337</div>
3338
3339<div class="slide">
3340 <h1>Native Delegation - Counter</h1>
3341
3342 <pre><code>package Stack;
3343use Moose;
3344
3345has depth =&gt; (
3346 traits =&gt; [ 'Counter' ],
3347 is =&gt; 'ro',
3348 isa =&gt; 'Int',
3349 default =&gt; 0,
3350 init_arg =&gt; undef,
3351 <span class="highlight">handles =&gt;
3352 { _inc_depth =&gt; 'inc',
3353 _dec_depth =&gt; 'dec',
3354 },</span>
3355);</code></pre>
3356</div>
3357
3358
3359<div class="slide">
5d572684 3360 <h1>Traits and Metaclasses</h1>
3361
3362 <ul>
3363 <li>The ultimate in customization</li>
3364 <li>Per attribute metaclasses</li>
3365 <li>Per attribute roles applied to the attribute metaclass</li>
3366 <li>Change the meta-level behavior</li>
3367 </ul>
3368</div>
3369
3370<div class="slide">
3371 <h1>Traits and Metaclasses</h1>
3372
3373 <ul>
3374 <li>The default metaclass is <code>Moose::Meta::Attribute</code></li>
3375 <li>Controls accessor generation, defaults, delegation, etc.</li>
3376 <li>Adding a role to this metaclass (or replacing it) allows for infinite customization</li>
3377 </ul>
3378</div>
3379
3380<div class="slide">
3381 <h1>Traits and Metaclasses</h1>
3382
3383 <ul>
3384 <li>Can add/alter/remove attribute parameter (from <code>has</code>)</li>
3385 <li>Can change behavior of created attribute</li>
3386 </ul>
3387</div>
3388
3389<div class="slide">
3390 <h1>Simple Trait Example</h1>
3391
3392 <pre><code>package Person;
3393use Moose;
3394use MooseX::LabeledAttributes;
3395
3396has ssn =&gt; (
3397 <span class="highlight">traits =&gt; [ 'Labeled' ],</span>
3398 is =&gt; 'ro',
3399 isa =&gt; 'Str',
3400 <span class="highlight">label =&gt; 'Social Security Number',</span>
3401);
3402
3403print <span class="highlight">Person-&gt;meta
3404 -&gt;get_attribute('ssn')-&gt;label;</span></code></pre>
3405</div>
3406
3407<div class="slide">
3408 <h1>Simple Metaclass Example</h1>
3409
3410 <pre><code>package Person;
3411use Moose;
3412use MooseX::LabeledAttributes;
3413
3414has ssn =&gt; (
3415 <span class="highlight">metaclass =&gt;
3416 'MooseX::Meta::Attribute::Labeled',</span>
3417 is =&gt; 'ro',
3418 isa =&gt; 'Str',
3419 <span class="highlight">label =&gt; 'Social Security Number',</span>
3420);
3421
3422print <span class="highlight">Person-&gt;meta
3423 -&gt;get_attribute('ssn')-&gt;label;</span></code></pre>
3424</div>
3425
3426<div class="slide">
3427 <h1>Traits vs Metaclass</h1>
3428
3429 <ul>
3430 <li>Can apply any mix of traits to an attribute</li>
3431 <li>But just one metaclass</li>
3432 <li>Traits (aka roles) can cooperate</li>
3433 <li>Metaclasses require you to pick just one</li>
3434 </ul>
3435</div>
3436
3437<div class="slide">
3438 <h1>Advanced Attributes Summary</h1>
3439
3440 <ul>
3441 <li>Use <code>weak_ref</code> to avoid circular references</li>
3442 <li>Use trigger to do an action post-attribute write</li>
3443 <li>Use delegations to hide "internal" objects</li>
3444 <li>Traits and metaclasses let you extend Moose's core attribute features</li>
3445 </ul>
3446</div>
3447
9186987b 3448<div class="slide">
3449 <h1>Questions?</h1>
3450</div>
3451
3452<div class="slide">
3453 <h1>Exercises</h1>
3454
3455 <pre># cd exercises
3456# perl bin/prove -lv t/06-advanced-attributes.t
3457
3458Iterate til this passes all its tests</pre>
3459</div>
3460
3461<div class="slide fake-slide0">
3462 <h1>Part 7: Introspection</h1>
3463</div>
3464
3465<div class="slide fake-slide0">
3466 <h1>Part 8: A Tour of MooseX</h1>
3467</div>
3468
3469<div class="slide fake-slide0">
3470 <h1>Part 9: Writing Moose Extensions</h1>
3471</div>
3472
8a719516 3473<div class="slide fake-slide0">
5e2eb691 3474 <h1>The End</h1>
8a719516 3475</div>
3476
3477<div class="slide">
3478 <h1>More Information</h1>
3479
3480 <ul>
3481 <li><a href="http://moose.perl.org/">http://moose.perl.org/</a></li>
3482 <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>
3483 <li><a href="irc://irc.perl.org/#moose">irc://irc.perl.org/#moose</a></li>
3484 <li>mailing list - <a href="mailto:moose@perl.org">moose@perl.org</a></li>
3485 <li>Slides and exercises are in Moose's git repo:
3486 <br />
5e2eb691 3487 <span style="white-space: nowrap">git://jules.scsys.co.uk/gitmo/moose-presentations</span></li>
8a719516 3488 </ul>
3489</div>
3490
55906a14 3491</div>
b751d33f 3492</body>
3493</html>
55906a14 3494
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3498
3499This work is licensed under a Creative Commons Attribution-Share Alike
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