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<title>Introduction to Moose</title>
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+ <br /><span xmlns:dc="http://purl.org/dc/elements/1.1/" href="http://purl.org/dc/dcmitype/Text" property="dc:title" rel="dc:type">Intro to Moose Class</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>.
+ </div>
+
<h2>Introduction to Moose</h2>
</div>
</div>
</ul>
</div>
-<div class="slide fake-slide0">
- <h1>Part 0: Moose Concepts</h1>
-</div>
-
<div class="slide">
- <h1>Moose background</h1>
+ <h1>Moose Background</h1>
<ul>
+ <li>Created by Stevan Little, first released in 2006</li>
<li>Moose builds on Perl 5's native OO</li>
<li>Borrows ideas from other languages, notably Perl 6</li>
<li>Provides semantics for common operations</li>
</ul>
</div>
+<div class="slide fake-slide0">
+ <h1>Part 0: Moose Concepts</h1>
+</div>
+
<div class="slide">
<h1>Classes</h1>
<pre><code>package Person;
use Moose;
-<span class="highlight">has 'first_name' => ( is => 'rw' );</span></code></pre>
+<span class="highlight">has first_name => ( is => 'rw' );</span></code></pre>
</div>
<pre><code>package Person;
use Moose;
-has 'weight' => ( is => 'ro', <span class="highlight">isa => 'Int'</span> );
+has weight => (
+ is => 'ro',
+ <span class="highlight">isa => 'Int'</span>,
+);
# kaboom
Person->new( weight => 'fat' );</code></pre>
<pre><code>package Person;
use Moose;
-has 'blog_uri' => (
+has blog_uri => (
is => 'rw',
isa => 'URI',
<span class="highlight">handles => { 'blog_hostname' => 'host' },</span>
);
<span class="highlight">$person->blog_hostname;</span>
-# really calls $person->blog_uri->host
+# really calls $person->blog_uri->host</code></pre>
</div>
<div class="slide">
<pre><code>package EvilEmployee;
use Moose;
extends 'Person';
-extends 'Thief';</pre></code>
+extends 'Thief';</code></pre>
<h2 class="right">RIGHT</h2>
<pre><code>package EvilEmployee;
use Moose;
-extends 'Person', 'Thief';</pre></code>
+extends 'Person', 'Thief';</code></pre>
</div>
<div class="slide">
<pre><code>package My::LWP;
use Moose;
-extends 'LWP';</pre></code>
+extends 'LWP';</code></pre>
<ul>
<li>No <code>Moose::Object</code>, so ...
<pre><code>package Employee;
use Moose;
-<span class="incremental current">extends 'Person';</span>
+<span class="current">extends 'Person';</span>
<span class="incremental">overrides</span> work => sub {
my $self = shift;
die "Pay me first" unless $self->got_paid;
<span class="incremental">super();</span>
}<span class="incremental">;</span></code></pre>
+</div>
<div class="slide">
<h1>Caveat <code>super</code></h1>
<pre><code>package Person;
use Moose;
-has 'first_name' => ( <span class="highlight">is => 'rw'</span> );
+has first_name => ( <span class="highlight">is => 'rw'</span> );
my $person =
Person->new( first_name => 'Dave' );
<pre><code>package Person;
use Moose;
-has 'first_name' => ( <span class="highlight">is => 'ro'</span> );
+has first_name => ( <span class="highlight">is => 'ro'</span> );
my $person =
Person->new( first_name => 'Dave' );
</div>
<div class="slide">
+ <h1>Classes Summary</h1>
+
+ <ul>
+ <li><code>use Moose</code></li>
+ <li><code>Class->meta</code></li>
+ <li><code>Moose::Object</code> base class</li>
+ <li><code>extends</code>, <code>overrides</code>, and <code>super</code></li>
+ <li>Simple attributes: <code>has</code>, <code>is => 'ro'</code>, & <code>is => 'rw'</code></li>
+ <li><code>no Moose</code></li>
+ <li><code>__PACKAGE__->meta->make_immutable</code></li>
+ </ul>
+</div>
+
+<div class="slide">
<h1>Exercises</h1>
<pre>$ cd exercises
# perl bin/prove -lv t/01-classes.t
-Iterate til this passes all its tests
+Iterate til this passes all its tests</pre>
+</div>
+
+<div class="slide fake-slide0">
+ <h1>Part 2: Roles</h1>
+</div>
+
+<div class="slide">
+ <h1>Just What Is a Role?</h1>
+
+ <ul>
+ <li>Mixin? Interface? Trait?</li>
+ <li>Yes ... and more!</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Roles Can Have State <strong>and</strong> Behavior</h1>
+
+ <pre><code>package HasPermissions;
+use Moose::Role;
+
+<span class="current"># state
+has access_level => ( is => 'rw' );</span>
+
+<span class="incremental"># behavior
+sub can_access {
+ my $self = shift;
+ my $required = shift;
+
+ return $self->access_level >= $required;
+}</span></code></pre>
+
+</div>
+
+<div class="slide">
+ <h1>Roles Can Define Interfaces</h1>
+
+ <pre><code>package Printable;
+use Moose::Role;
+
+requires 'as_string';</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Roles Can Do All Three</h1>
+
+ <pre><code>package Printable;
+use Moose::Role;
+
+requires 'as_string';
+
+has has_been_printed => ( is => 'rw' );
+
+sub print {
+ my $self = shift;
+ print $self->as_string;
+ $self->has_been_printed(1);
+}</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Classes Consume Roles</h1>
+
+ <pre><code>package Person;
+use Moose;
+
+with 'HasPermissions';</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Classes Consume Roles</h1>
+
+<pre><code>my $person = Person->new(
+ first_name => 'Kenichi',
+ last_name => 'Asai',
+ access_level => 42,
+);
+
+print $person->full_name
+ . ' has '
+ . $person->can_access(42)
+ ? 'great power'
+ : 'little power';</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Roles in Practice</h1>
+
+ <ul>
+ <li>Consuming a role =~ inlining the role</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>In Other Words ...</h1>
+
+<pre><code>package Person;
+use Moose;
+
+<span class="highlight">with 'Printable';</span></code></pre>
+</div>
+
+<div class="slide">
+ <h1>In Other Words ...</h1>
+
+<pre><code>package Person;
+use Moose;
+
+<span class="delete">with 'Printable';</span>
+
+<span class="highlight">has has_been_printed => ( is => 'rw' );
+
+sub print {
+ my $self = shift;
+ print $self->as_string;
+ $self->has_been_printed(1);
+}</span></code></pre>
+</div>
+
+<div class="slide">
+ <h1>Except</h1>
+
+ <ul>
+ <li>Role consumption is introspectable</li>
+ </ul>
+
+ <pre><code>if ( Person->does('Printable') ) { ... }
+
+# or ...
+
+if ( Person->meta->does('Printable') ) { ... }</code></pre>
+
+</div>
+
+<div class="slide">
+ <h1>These Names Are the Same</h1>
+
+ <ul>
+ <li>What if a role and class define the same method?</li>
+ <li>A class's <em>local</em> methods win over the role's</li>
+ <li>The role's methods win over the class's <em>inherited</em> methods</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Conflicts Between Roles</h1>
+
+ <ul>
+ <li>Two roles with a method of the same name</li>
+ <li>Generates a compile-time error when consumed by a class</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Conflict Example</h1>
+
+ <pre><code>package IsFragile;
+use Moose::Role;
+
+sub break { ... }
+
+package CanBreakdance;
+use Moose::Role;
+
+sub break { ... }</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Conflict Example</h1>
+
+ <pre><code>package FragileDancer;
+use Moose;
+
+<span class="highlight">with 'IsFragile', 'CanBreakdance';</span></code></pre>
+
+ <ul>
+ <li>Only one <code>with</code>!</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Conflict Resolution</h1>
+
+ <ul>
+ <li>The consuming class must resolve the conflict by implementing th emethod</li>
+ <li>Can use some combination of method exclusion and aliasing</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Method Aliasing</h1>
+
+ <pre><code>package FragileDancer;
+use Moose;
+
+<span class="highlight">with 'IsFragile' =>
+ { alias =>
+ { break => 'break_bone' } },
+ 'CanBreakdance' =>
+ { alias =>
+ { break => 'break_it_down' } };</span></code></pre>
+
+ <ul>
+ <li>Renames the roles' methods</li>
+ <li>Still conflicts, need to <code>exclude</code> as well</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Method Exclusion</h1>
+
+ <pre><code>package FragileDancer;
+use Moose;
+
+<span class="highlight">with 'IsFragile' =>
+ { alias =>
+ { break => 'break_bone' },
+ exclude => 'break' },
+ 'CanBreakdance' =>
+ { alias =>
+ { break => 'break_dance' },
+ exclude => 'break' };</span></code></pre>
+</div>
+
+<div class="slide">
+ <h1>And then ...</h1>
+
+ <pre><code>package FragileDancer;
+use Moose;
+sub break {
+ my $self = shift;
+
+ $self->break_dance;
+ if ( rand(1) < 0.5 ) {
+ $self->break_bone;
+ }
+}</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Still Full of Fail</h1>
+
+ <ul>
+ <li>Roles are also about semantics!</li>
+ <li>We've fulfilled the letter and lost the spirit</li>
+ <li>Roles have a <em>meaning</em></li>
+ <li>Think twice before blindly aliasing and excluding methods!</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Hot Role-on-Role Action</h1>
+
+ <pre><code>package Comparable;
+use Moose::Role;
+
+requires 'compare';</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Hot Role-on-Role Action</h1>
+
+ <pre><code>package TestsEquality;
+use Moose::Role;
+
+with 'Comparable';
+
+sub is_equal {
+ my $self = shift;
+ return $self->compare(@_) == 0;
+}</code></pre>
+</div>
+
+<div class="slide">
+ <h1>And then ...</h1>
+
+ <pre><code>package Integer;
+use Moose;
+
+with 'TestsEquality';
+
+# Satisfies the Comparable role
+sub compare { ... }
+
+Integer->does('TestsEquality'); # true
+Integer->does('Comparable'); # also true!</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Name Conflicts Between Roles</h1>
+
+ <pre><code>package HasSubProcess;
+use Moose::Role;
+
+<span class="highlight">sub execute { ... }</span>
+
+package Killer;
+use Moose::Role;
+
+with 'HasSubProcess';
+
+<span class="highlight">sub execute { ... }</span></code></pre>
+</div>
+
+<div class="slide">
+ <h1>Delayed Conflict</h1>
+
+ <pre><code>package StateOfTexas;
+with 'Killer';</code></pre>
+
+ <ul>
+ <li><code>StateOfTexas</code> must implement its own <code>execute</code></li>
+ <li>But loading the <code>Killer</code> role by itself does not cause an error</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Roles as Interfaces</h1>
+
+ <ul>
+ <li>Roles can <code>require</code> methods of their consumers</li>
+ <li>Compile-time checks</li>
+ <li>Method must exist when the role is consumed</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>The Attribute Gotcha</h1>
+
+<pre><code>package HasSize;
+use Moose::Role;
+
+<span class="current">requires 'size';</span>
+
+package Shirt;
+use Moose;
+
+<span class="incremental">with 'HasSize';
+
+has size => ( is => 'ro' );</span></code></pre>
+</div>
+
+<div class="slide">
+ <h1>The Attribute Gotcha Workaround</h1>
+
+ <pre><code>package HasSize;
+use Moose::Role;
+
+requires 'size';
+
+package Shirt;
+use Moose;
+
+has size => ( is => 'ro' );
+
+with 'HasSize';</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Compile-time Is a Lie</h1>
+
+ <ul>
+ <li>Really, it's <em>package load</em> time</li>
+ <li>That's run-time, but before the "real" run-time</li>
+ <li>Moose does not rewire Perl, it's just sugar!</li>
+ <li>(but <code>MooseX::Declare</code> <em>does</em> rewire Perl)</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Enforcing Roles</h1>
+
+ <pre><code>package Comparison;
+use Moose;
+
+has [ 'left', 'right' ] => (
+ is => 'ro',
+ <span class="highlight">does => 'Comparable',</span>
+);
+</code></pre>
+
+ <ul>
+ <li>A sneak peek at type constraints</li>
+ </ul>
+</div>
+
+
+<div class="slide">
+ <h1>Roles Can Be Applied to Objects</h1>
+
+ <pre><code>use Moose::Util qw( apply_all_roles );
+
+my $fragile_person = Person->new( ... );
+apply_all_roles( $fragile_person, 'IsFragile' );</code></pre>
+
+ <ul>
+ <li>Does not change the <code>Person</code> class</li>
+ <li>Works with non-Moose classes, great for monkey-patching!</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Roles Are Dirty Too</h1>
+
+ <ul>
+ <li>Once again, clean up those Moose droppings</li>
+ </ul>
+
+ <pre><code>package Comparable;
+use Moose::Role;
+
+requires 'compare';
+
+<span class="highlight">no Moose::Role;</span></code></pre>
+
+ <ul>
+ <li>But roles cannot be made immutable</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>The Zen of Roles</h1>
+
+ <ul>
+ <li>Roles represent discrete units of ...
+ <ul>
+ <li>state</li>
+ <li>behavior</li>
+ <li>interface</li>
+ </ul>
+ </li>
+ <li>Roles are shareable between unrelated classes</li>
+ <li>Roles are what a class <em>does</em>, not what it <em>is</em></li>
+ <li>Roles <em>add</em> functionality, inheritance <em>specializes</em></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Abstract Examples</h1>
+
+ <ul>
+ <li>Human <em>@ISA</em> Animal</li>
+ <li>Human <em>does</em> Toolmaker (as <em>does</em> Chimpanzee)</li>
+ <li>Car <em>@ISA</em> Vehicle</li>
+ <li>Car <em>does</em> HasEngine</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Real Examples</h1>
+
+ <ul>
+ <li>Objects representing SQL database components and queries
+ <ul>
+ <li>Schema, Table, Column, ColumnAlias</li>
+ <li>Select, Insert, Update, Delete</li>
+ </ul>
+ </li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Real Examples</h1>
+
+ <ul>
+ <li>Column and ColumnAlias both <em>do</em> ColumnLike</li>
+ <li>ColumnLike things can be used in certain parts of queries</li>
+ <li>All queries <em>do</em> HasWhereClause</li>
+ <li>Select <em>does</em> Comparable and Selectable (for subselects)</li>
+ <li>A where clause requires its components to <em>do</em> Comparable</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Exercises</h1>
+
+ <pre>$ cd exercises
+# perl bin/prove -lv t/02-roles.t
+
+Iterate til this passes all its tests</pre>
+</div>
+
+</div>
</body>
</html>
+
+<!--
+
+Copyright 2009 David Rolsky. All Rights Reserved.
+
+This work is licensed under a Creative Commons Attribution-Share Alike
+3.0 United States License See
+http://creativecommons.org/licenses/by-sa/3.0/us/ for details.
+
+-->
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