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7<title>Introduction to Moose</title>
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11<meta name="author" content="Eric A. Meyer" />
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37<div class="layout">
38<div id="controls"><!-- DO NOT EDIT --></div>
39<div id="currentSlide"><!-- DO NOT EDIT --></div>
40<div id="header"></div>
41<div id="footer">
42 <h2>Introduction to Moose</h2>
43</div>
44</div>
45
46<div class="presentation">
47
48<div class="slide">
49 <h1>Introduction to Moose</h1>
50 <h2>YAPC 2009</h2>
51</div>
52
53<div class="slide">
54 <h1>Moose Summed Up</h1>
55
56 <ul>
57 <li><strong>Declarative</strong> OO sugar</li>
58 <li>Introspectable</li>
59 <li>Extensible</li>
60 </ul>
61</div>
62
63<div class="slide">
64 <h1>Concepts</h1>
65
66 <ul>
67 <li>Moose builds on Perl 5's native OO</li>
68 <li>Borrows ideas from other languages, notably Perl 6</li>
69 <li>Provides semantics for common operations</li>
70 </ul>
71</div>
72
73<div class="slide">
74 <h1>Classes</h1>
75
76 <ul>
77 <li>
78 Classes have ...
79 <ul>
80 <li>Attributes</li>
81 <li>Methods</li>
82 <li>Superclasses</li>
83 <li>Method modifiers</li>
84 <li>Constructor and destructor</li>
85 <li>One metaclass object</li>
86 </ul>
87 </li>
88 <li>Classes do roles</li>
89 </ul>
90</div>
91
92<div class="slide">
93 <h1>Class Example</h1>
94
95 <pre><code>package Person;
96<span class="highlight">use Moose;</span></code></pre>
97
98 <ul>
99 <li>Poof, a Moose-based class!</li>
100 </ul>
101</div>
102
103<div class="slide">
104 <h1>Attributes</h1>
105
106 <ul>
107 <li>Aka property, slot, field, member variable</li>
108 <li>A piece of data owned by an object</li>
109 </ul>
110</div>
111
112<div class="slide">
113 <h1>Attributes</h1>
114
115 <ul>
116 <li>
117 Attributes have ...
118 <ul>
119 <li>Access-control (read-only vs read-write)</li>
120 <li>An optional type</li>
121 <li>Accessor methods</li>
122 <li>Delegation methods</li>
123 <li>Optional default value</li>
124 <li>Many more features</li>
125 </ul>
126 </li>
127 <li>Stored in the object, but don't worry about that</li>
128 </ul>
129</div>
130
131<div class="slide">
132 <h1>Attribute Example</h1>
133
134 <pre><code>package Person;
135use Moose;
136
137<span class="highlight">has 'first_name' =&gt; ( is =&gt; 'rw' );</span></code></pre>
138
139</div>
140
141<div class="slide">
142 <h1>Methods</h1>
143
144 <ul>
145 <li>Nothing fancy here, just Perl subroutines</li>
146 </ul>
147
148 <pre><code>package Person;
149use Moose;
150
151<span class="highlight">sub greet { ... }</span></code></pre>
152</div>
153
154<div class="slide">
155 <h1>Roles</h1>
156
157 <ul>
158 <li>Classes <strong>do</strong> (or consume) roles</li>
159 <li>Similar to mixins and Java interfaces</li>
160 </ul>
161</div>
162
163<div class="slide">
164 <h1>Roles</h1>
165
166 <ul>
167 <li>Like classes, can have attributes, methods, do roles</li>
168 <li>Roles can require methods</li>
169 <li>Roles are composed (flattened) into classes</li>
170 </ul>
171</div>
172
173<div class="slide">
174 <h1>Role Example</h1>
175
176<pre><code>package HasPermissions;
177<span class="highlight">use Moose::Role;</span>
178
179has is_admin =&gt; ( is =&gt; 'rw' );</code></pre>
180</div>
181
182<div class="slide">
183 <h1>Role Example</h1>
184
185 <p>
186 And then ...
187 </p>
188
189<pre><code>package Person;
190use Moose;
191
192<span class="highlight">with 'HasPermissions';</span></code></pre>
193</div>
194
195<div class="slide">
196 <h1>Method Modifiers</h1>
197
198 <ul>
199 <li>AKA advice</li>
200 <li>&quot;<strong>Before</strong> foo(), do this first&quot;</li>
201 <li>&quot;Do this <strong>after</strong> foo()</li>
202 <li>&quot;Put this code <strong>around</strong> foo()&quot;</li>
203 </ul>
204</div>
205
206<div class="slide">
207 <h1>Before &amp; After</h1>
208
209<pre><code>before 'foo'
210 =&gt; sub { warn 'About to call foo()' };
211
212after 'foo'
213 =&gt; sub { warn 'Leaving foo()' };</code></pre>
214
215</div>
216
217<div class="slide">
218 <h1>Around</h1>
219
220<pre><code>around 'foo' =&gt; sub {
221 my $real_foo = shift;
222 my $self = shift;
223
224 warn 'Just before foo()';
225 my @return =
226 $self-&gt;$real_foo( @_, bar =&gt; 42 );
227
228 return ( @return, 'modify return values' );
229};</code></pre>
230</div>
231
232<div class="slide">
233 <h1>Type Constraints</h1>
234
235 <ul>
236 <li>NOT A FULL-BLOWN TYPE SYSTEM!</li>
237 <li>But still darn useful</li>
238 <li>Constrain attribute values</li>
239 <li>Coerce from other types</li>
240 </ul>
241</div>
242
243<div class="slide">
244 <h1>Type Constraint Example</h1>
245
246<pre><code>package Person;
247use Moose;
248
249has 'weight' =&gt; ( is =&gt; 'ro', <span class="highlight">isa =&gt; 'Int'</span> );
250
251# kaboom
252Person-&gt;new( weight =&gt; 'fat' );</code></pre>
253</div>
254
255<div class="slide">
256 <h1>Delegation</h1>
257
258 <ul>
259 <li>Attributes can define delegations</li>
260 <li>Lets you hide some implementation details</li>
261 <li>Fewer objects to chase around</li>
262 </ul>
263</div>
264
265<div class="slide">
266 <h1>Delegation</h1>
267
268<pre><code>package Person;
269use Moose;
270
271has 'blog_uri' =&gt; (
272 is =&gt; 'rw',
273 isa =&gt; 'URI',
274 <span class="highlight">handles =&gt; { 'blog_hostname' =&gt; 'host' },</span>
275);
276
277<span class="highlight">$person->blog_hostname;</span>
278# really calls $person->blog_uri->host
279</div>
280
281<div class="slide">
282 <h1>Constructors</h1>
283
284 <ul>
285 <li>Moose creates <code>new()</code> for you</li>
286 <li>Provide an optional <code>BUILDARGS()</code> and <code>BUILD()</code></li>
287 </ul>
288</div>
289
290<div class="slide">
291 <h1>Destructors</h1>
292
293 <ul>
294 <li>Provide an optional <code>DEMOLISH()</code></li>
295 </ul>
296</div>
297
298<div class="slide">
299 <h1>Moose Meta-API</h1>
300
301 <ul>
302 <li>Answers questions like ...
303 <ul>
304 <li>What methods does this class have?</li>
305 <li>What are its parents?</li>
306 <li>What attributes does it have (including inherited attributes)?</li>
307 <li>What roles does it do?</li>
308 <li>Much, much, more</li>
309 </ul>
310 </li>
311 </ul>
312</div>
313
314<div class="slide">
315 <h1>Moose Meta-API</h1>
316
317 <ul>
318 <li>Not just for introspection ...
319 <ul>
320 <li>Add methods, attributes, roles, etc</li>
321 <li>Extend and alter core features</li>
322 </ul>
323 </li>
324 </ul>
325</div>
326
327<div class="slide">
328 <h1>Why Moose?</h1>
329
330 <ul>
331 <li>A quick bit of propoganda ...</li>
332 </ul>
333</div>
334
335<div class="slide">
336 <h1>With Moose</h1>
337
338 <pre><code>package Person;
339use Moose;
340
341has last_name =&gt; (
342 is =&gt; 'rw',
343 isa =&gt; 'Str',
344);</code></pre>
345</div>
346
347<div class="slide">
348 <h1>Without Moose</h1>
349
350 <pre class="small"><code>package Person;
351use strict;
352use warnings;
353use Carp 'confess';
354
355sub new {
356 my $class = shift;
357 my %args = @_;
358 my $self = {};
359
360 if (exists $args{last_name}) {
361 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
362 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
363 if ref($args{last_name});
364 $self-&gt;{last_nane} = $args{last_name};
365 }
366
367 return bless $self, $class;
368}
369
370sub last_name {
371 my $self = shift;
372
373 if (@_) {
374 my $value = shift;
375 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
376 . &quot;Validation failed for 'Str' with value $value&quot;
377 if ref($value);
378 $self-&gt;{last_name} = $value;
379 }
380
381 return $self-&gt;{last_name};
382}</code></pre>
383
384</div>
385
386<div class="slide">
387 <h1>Side by side</h1>
388
389 <table class="side-by-side">
390 <tr>
391 <td>
392 <pre><code>package Person;
393use Moose;
394
395has last_name =&gt; (
396 is =&gt; 'rw',
397 isa =&gt; 'Str',
398);</code></pre>
399 </td>
400 <td>
401 <pre class="small"><code>package Person;
402use strict;
403use warnings;
404use Carp 'confess';
405
406sub new {
407 my $class = shift;
408 my %args = @_;
409 my $self = {};
410
411 if (exists $args{last_name}) {
412 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
413 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
414 if ref($args{last_name});
415 $self-&gt;{last_nane} = $args{last_name};
416 }
417
418 return bless $self, $class;
419}
420
421sub last_name {
422 my $self = shift;
423
424 if (@_) {
425 my $value = shift;
426 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
427 . &quot;Validation failed for 'Str' with value $value&quot;
428 if ref($value);
429 $self-&gt;{last_name} = $value;
430 }
431
432 return $self-&gt;{last_name};
433}</code></pre>
434 </td>
435 </tr>
436 </table>
437
438</div>
439
440<div class="slide">
441 <h1>Side by side</h1>
442
443 <table class="side-by-side">
444 <tr>
445 <td>
446 <pre><code><span class="match-moose">package Person;</span>
447use Moose;
448
449has last_name =&gt; (
450 is =&gt; 'rw',
451 isa =&gt; 'Str',
452);</code></pre>
453 </td>
454 <td>
455 <pre class="small"><code><span class="match-unsweet">package Person;</span>
456use strict;
457use warnings;
458use Carp 'confess';
459
460sub new {
461 my $class = shift;
462 my %args = @_;
463 my $self = {};
464
465 if (exists $args{last_name}) {
466 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
467 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
468 if ref($args{last_name});
469 $self-&gt;{last_nane} = $args{last_name};
470 }
471
472 return bless $self, $class;
473}
474
475sub last_name {
476 my $self = shift;
477
478 if (@_) {
479 my $value = shift;
480 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
481 . &quot;Validation failed for 'Str' with value $value&quot;
482 if ref($value);
483 $self-&gt;{last_name} = $value;
484 }
485
486 return $self-&gt;{last_name};
487}</code></pre>
488 </td>
489 </tr>
490 </table>
491</div>
492
493<div class="slide">
494 <h1>Side by side</h1>
495
496 <table class="side-by-side">
497 <tr>
498 <td>
499 <pre><code>package Person;
500<span class="match-moose">use Moose;</span>
501
502has last_name =&gt; (
503 is =&gt; 'rw',
504 isa =&gt; 'Str',
505);</code></pre>
506 </td>
507 <td>
508 <pre class="small"><code>package Person;
509<span class="match-unsweet">use strict;
510use warnings;
511use Carp 'confess';
512
513sub new {
514 my $class = shift;
515 my %args = @_;
516 my $self = {};</span>
517
518 if (exists $args{last_name}) {
519 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
520 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
521 if ref($args{last_name});
522 $self-&gt;{last_nane} = $args{last_name};
523 }
524
525 <span class="match-unsweet">return bless $self, $class;
526}</span>
527
528sub last_name {
529 my $self = shift;
530
531 if (@_) {
532 my $value = shift;
533 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
534 . &quot;Validation failed for 'Str' with value $value&quot;
535 if ref($value);
536 $self-&gt;{last_name} = $value;
537 }
538
539 return $self-&gt;{last_name};
540}</code></pre>
541 </td>
542 </tr>
543 </table>
544</div>
545
546<div class="slide">
547 <h1>Side by side</h1>
548
549 <table class="side-by-side">
550 <tr>
551 <td>
552 <pre><code>package Person;
553use Moose;
554
555<span class="match-moose">has last_name =&gt; (</span>
556 is =&gt; 'rw',
557 isa =&gt; 'Str',
558<span class="match-moose">);</span></code></pre>
559 </td>
560 <td>
561 <pre class="small"><code>package Person;
562use strict;
563use warnings;
564use Carp 'confess';
565
566sub new {
567 my $class = shift;
568 my %args = @_;
569 my $self = {};
570
571 <span class="match-unsweet">if (exists $args{last_name}) {</span>
572 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
573 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
574 if ref($args{last_name});
575 <span class="match-unsweet">$self-&gt;{last_nane} = $args{last_name};
576 }</span>
577
578 return bless $self, $class;
579}
580
581sub last_name {
582 my $self = shift;
583
584 if (@_) {
585 my $value = shift;
586 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
587 . &quot;Validation failed for 'Str' with value $value&quot;
588 if ref($value);
589 $self-&gt;{last_name} = $value;
590 }
591
592 return $self-&gt;{last_name};
593}</code></pre>
594 </td>
595 </tr>
596 </table>
597</div>
598
599<div class="slide">
600 <h1>Side by side</h1>
601
602 <table class="side-by-side">
603 <tr>
604 <td>
605 <pre><code>package Person;
606use Moose;
607
608has last_name =&gt; (
609 <span class="match-moose">is =&gt; 'rw',</span>
610 isa =&gt; 'Str',
611);</code></pre>
612 </td>
613 <td>
614 <pre class="small"><code>package Person;
615use strict;
616use warnings;
617use Carp 'confess';
618
619sub new {
620 my $class = shift;
621 my %args = @_;
622 my $self = {};
623
624 if (exists $args{last_name}) {
625 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
626 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
627 if ref($args{last_name});
628 $self-&gt;{last_nane} = $args{last_name};
629 }
630
631 return bless $self, $class;
632}
633
634<span class="match-unsweet">sub last_name {
635 my $self = shift;
636
637 if (@_) {
638 my $value = shift;</span>
639 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
640 . &quot;Validation failed for 'Str' with value $value&quot;
641 if ref($value);
642 <span class="match-unsweet">$self-&gt;{last_name} = $value;
643 }
644
645 return $self-&gt;{last_name};
646}</span></code></pre>
647 </td>
648 </tr>
649 </table>
650</div>
651
652<div class="slide">
653 <h1>Side by side</h1>
654
655 <table class="side-by-side">
656 <tr>
657 <td>
658 <pre><code>package Person;
659use Moose;
660
661has last_name =&gt; (
662 is =&gt; 'rw',
663 <span class="match-moose">isa =&gt; 'Str',</span>
664);</code></pre>
665 </td>
666 <td>
667 <pre class="small"><code>package Person;
668use strict;
669use warnings;
670use Carp 'confess';
671
672sub new {
673 my $class = shift;
674 my %args = @_;
675 my $self = {};
676
677 if (exists $args{last_name}) {
678 <span class="match-unsweet">confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
679 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
680 if ref($args{last_name});</span>
681 $self-&gt;{last_nane} = $args{last_name};
682 }
683
684 return bless $self, $class;
685}
686
687sub last_name {
688 my $self = shift;
689
690 if (@_) {
691 my $value = shift;
692 <span class="match-unsweet">confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
693 . &quot;Validation failed for 'Str' with value $value&quot;
694 if ref($value);</span>
695 $self-&gt;{last_name} = $value;
696 }
697
698 return $self-&gt;{last_name};
699}</code></pre>
700 </td>
701 </tr>
702 </table>
703</div>
704
705<div class="slide">
706 <h1>Side by side</h1>
707
708 <table class="side-by-side">
709 <tr class="incremental">
710 <td>5 lines</td>
711 <td>21 lines</td>
712 </tr>
713 <tr class="incremental">
714 <td>92 characters</td>
715 <td>741 characters</td>
716 </tr>
717 <tr>
718 <td>
719 <pre><code>package Person;
720use Moose;
721
722has last_name =&gt; (
723 is =&gt; 'rw',
724 isa =&gt; 'Str',
725);</code></pre>
726 </td>
727 <td>
728 <pre class="small"><code>package Person;
729use strict;
730use warnings;
731use Carp 'confess';
732
733sub new {
734 my $class = shift;
735 my %args = @_;
736 my $self = {};
737
738 if (exists $args{last_name}) {
739 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
740 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
741 if ref($args{last_name});
742 $self-&gt;{last_nane} = $args{last_name};
743 }
744
745 return bless $self, $class;
746}
747
748sub last_name {
749 my $self = shift;
750
751 if (@_) {
752 my $value = shift;
753 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
754 . &quot;Validation failed for 'Str' with value $value&quot;
755 if ref($value);
756 $self-&gt;{last_name} = $value;
757 }
758
759 return $self-&gt;{last_name};
760}</code></pre>
761 </td>
762 </tr>
763 </table>
764</div>
765
766<div class="slide">
767 <h1>Typo?</h1>
768
769 <pre class="small"><code>sub new {
770 my $class = shift;
771 my %args = @_;
772 my $self = {};
773
774 if (exists $args{last_name}) {
775 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
776 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
777 if ref($args{last_name});
778 $self-&gt;{last_nane} = $args{last_name};
779 }
780
781 return bless $self, $class;
782}</code></pre>
783</div>
784
785<div class="slide">
786 <h1>Typo?</h1>
787
788 <pre class="small"><code>if (exists $args{last_name}) {
789 confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
790 . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
791 if ref($args{last_name});
792 $self-&gt;{last_nane} = $args{last_name};
793}</code></pre>
794</div>
795
796<div class="slide">
797 <h1>Typo?</h1>
798
799 <code>$self-&gt;{last_nane} = $args{last_name};</code>
800</div>
801
802<div class="slide">
803 <h1>Typo?</h1>
804 <code>$self-&gt;{last_na<span class="highlight">n</span>e}</code>
805</div>
806
807<div class="slide">
808 <h1>Why Moose?</h1>
809
810 <pre><code>package Person;
811use Moose;
812
813has last_name =&gt; (
814 is =&gt; 'rw',
815 isa =&gt; 'Str',
816);</code></pre>
817</div>
818
819<div class="slide fake-slide0">
820 <h1>Moose Classes</h1>
821</div>
822
823<div class="slide">
824 <h1>Moose Classes</h1>
825
826 <ul>
827 <li>Moose classes are Perl packages which <code>use Moose</code></li>
828 </ul>
829</div>
830
831<div class="slide">
832 <h1>Moose.pm and Your Class</h1>
833
834 <pre><code>package Person;
835use Moose;</code></pre>
836
837 <ul>
838 <li><code>Moose.pm</code> provides declarative sugar</li>
9b195048 839 <li>Turns on <code>strict</code> and <code>warnings</code></li>
b751d33f 840 <li>Creates metaclasses for your class: <code>Person-&gt;meta</code></li>
841 <li>Moose classes automatically inherit from <code>Moose::Object</code></li>
842 </ul>
843</div>
844
845<div class="slide">
846 <h1>What <code>Moose::Object</code> Provides</h1>
847
848 <ul>
849 <li>Constructor - <code>new()</code></li>
850 <li>Calls your <code>BUILDARGS()</code> and/or <code>BUILD()</code></li>
851 <li>Calls your <code>DEMOLISH</code> during object destruction</li>
852 </ul>
853</div>
854
855<div class="slide">
856 <h1>extends</h1>
857
858 <ul>
859 <li><code>extends</code> is sugar for declaring parent classes</li>
860 </ul>
861
862 <pre><code>package Employee;
863use Moose;
864<span class="highlight">extends 'Person';</span></code></pre>
865</div>
866
867<div class="slide">
868 <h1>extends</h1>
869
870 <ul>
871 <li>Each call to <code>extends</code> <strong>resets</strong> your parents</li>
872 </ul>
873
874 <h2 class="wrong">WRONG</h2>
875
9b195048 876 <pre><code>package EvilEmployee;
b751d33f 877use Moose;
878extends 'Person';
879extends 'Thief';</pre></code>
880
881 <h2 class="right">RIGHT</h2>
882
9b195048 883 <pre><code>package EvilEmployee;
b751d33f 884use Moose;
885extends 'Person', 'Thief';</pre></code>
886</div>
887
888<div class="slide">
889 <h1>Extending un-Moose-y Parents</h1>
890
891 <pre><code>package My::LWP;
892use Moose;
893extends 'LWP';</pre></code>
894
895 <ul>
896 <li>No <code>Moose::Object</code>, so ...
897 <ul>
898 <li>No attribute-handling <code>new()</code></li>
899 <li>No <code>BUILDARGS()</code> or <code>BUILD()</code></li>
900 <li>No <code>DEMOLISH()</code></li>
901 </ul>
902 </li>
903 <li>But see <code>MooseX::NonMoose</code> for a workaround</li>
904 </ul>
905</div>
906
907<div class="slide">
9b195048 908 <h1><code>overrides</code> and <code>super</code></h1>
909
910 <ul>
911 <li><code>overrides</code> is another method modifier</li>
912 <li>An alternative to Perl's <code>SUPER::</code></li>
913 </ul>
914</div>
915
916<div class="slide">
917 <h1><code>overrides</code> and <code>super</code></h1>
918
919 <pre><code>package Employee;
920use Moose;
921
922<span class="incremental current">extends 'Person';</span>
923
924<span class="incremental">overrides</span> work =&gt; sub {
925 my $self = shift;
926
927 die "Pay me first" unless $self-&gt;got_paid;
928 <span class="incremental">super();</span>
929}<span class="incremental">;</span></code></pre>
930
931<div class="slide">
932 <h1>Caveat <code>super</code></h1>
933
934 <ul>
935 <li>Mostly like <code>$self-&gt;SUPER::work(@_)</code></li>
936 <li><strong>But</strong> cannot change <code>@_</code>!</li>
937 <li>Binds the parent's method at compile time</li>
938 </ul>
939</div>
940
941<div class="slide">
942 <h1>Attributes (Part 1)</h1>
943
944 <ul>
945 <li><code>has 'foo'</code></li>
946 <li>Use <code>is =&gt; 'ro'</code> or <code>is =&gt; 'rw'</code></li>
947 <li>Attributes without "is" have no accessors</li>
948 </ul>
949</div>
950
951<div class="slide">
952 <h1>Read-write attributes</h1>
953
954 <pre><code>package Person;
955use Moose;
956
957has 'first_name' =&gt; ( <span class="highlight">is =&gt; 'rw'</span> );
958
959my $person =
960 Person-&gt;new( first_name =&gt; 'Dave' );
961
962$person-&gt;first_name('Stevan');
963print $person-&gt;first_name; # Stevan</code></pre>
964
965</div>
966
967<div class="slide">
968 <h1>Read-only attributes</h1>
969
970 <pre><code>package Person;
971use Moose;
972
973has 'first_name' =&gt; ( <span class="highlight">is =&gt; 'ro'</span> );
974
975my $person =
976 Person-&gt;new( first_name =&gt; 'Dave' );
977
978$person-&gt;first_name('Stevan');
979print $person-&gt;first_name; # Dave</code></pre>
980
981</div>
982
983<div class="slide">
984 <h1>There is More to Come</h1>
985
986 <ul>
987 <li>Attributes have a <em>lot</em> of features</li>
988 </ul>
989</div>
990
991<div class="slide">
b751d33f 992 <h1>Cleaning Up Moose Droppings</h1>
993
994 <pre><code>package Person;
995use Moose;
996
997# true
998Person->can('extends');</code></pre>
999
1000 <ul>
1001 <li>Not very hygienic</li>
1002 </ul>
1003</div>
1004
1005<div class="slide">
1006 <h1>Cleaning Up Moose Droppings</h1>
1007
1008 <pre><code>package Person;
1009use Moose;
1010
1011...
1012
1013no Moose;
1014
1015# false
1016Person->can('extends');</code></pre>
1017</div>
1018
1019<div class="slide">
1020 <h1>No Moose</h1>
1021
1022 <ul>
1023 <li><code>no Moose</code> at the end of a package is a best practice</li>
1024 <li>Just do it</li>
1025 </ul>
1026</div>
1027
1028<div class="slide">
1029 <h1>Immutability</h1>
1030
1031 <ul>
1032 <li><span style="font-family: URW Chancery L; font-size: 140%">Stevan's Incantation of Fleet-Footedness</span></li>
1033 </ul>
1034
1035 <pre><code>package Person;
1036use Moose;
1037
1038<span class="highlight">__PACKAGE__->meta->make_immutable;</span></code></pre>
1039</div>
1040
9b195048 1041<div class="slide">
1042 <h1>What <code>make_immutable</code> does</h1>
1043
1044 <ul>
1045 <li>Magic</li>
1046 <li>Uses <code>eval</code> to "inline" a constructor</li>
1047 <li>Memoizes a lot of meta-information</li>
1048 <li>Makes loading your class slower</li>
1049 <li>Makes object creation <em>much</em> faster</li>
1050 </ul>
1051</div>
1052
1053<div class="slide">
1054 <h1>When to Immutabilize?</h1>
1055
1056 <ul>
1057 <li><em>Almost</em> always</li>
1058 <li>Startup time vs execution time</li>
1059 </ul>
1060</div>
1061
b751d33f 1062</body>
1063</html>
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