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  <h2>Introduction to Moose</h2>
</div>
</div>

<div class="presentation">

<div class="slide">
  <h1>Introduction to Moose</h1>
  <h2>YAPC 2009</h2>
</div>

<div class="slide">
  <h1>Moose Summed Up</h1>

  <ul>
    <li><strong>Declarative</strong> OO sugar</li>
    <li>Introspectable</li>
    <li>Extensible</li>
  </ul>
</div>

<div class="slide fake-slide0">
  <h1>Part 0: Moose Concepts</h1>
</div>

<div class="slide">
  <h1>Moose background</h1>

  <ul>
    <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">
  <h1>Classes</h1>

  <ul>
    <li>
      Classes have ...
      <ul>
        <li>Attributes</li>
        <li>Methods</li>
        <li>Superclasses</li>
        <li>Method modifiers</li>
        <li>Constructor and destructor</li>
        <li>One metaclass object</li>
      </ul>
    </li>
    <li>Classes do roles</li>
  </ul>
</div>

<div class="slide">
  <h1>Class Example</h1>

  <pre><code>package Person;
<span class="highlight">use Moose;</span></code></pre>

  <ul>
    <li>Poof, a Moose-based class!</li>
  </ul>
</div>

<div class="slide">
  <h1>Attributes</h1>

  <ul>
    <li>Aka property, slot, field, member variable</li>
    <li>A piece of data owned by an object</li>
  </ul>
</div>

<div class="slide">
  <h1>Attributes</h1>

  <ul>
    <li>
      Attributes have ...
      <ul>
        <li>Access-control (read-only vs read-write)</li>
        <li>An optional type</li>
        <li>Accessor methods</li>
        <li>Delegation methods</li>
        <li>Optional default value</li>
        <li>Many more features</li>
      </ul>
    </li>
    <li>Stored in the object, but don't worry about that</li>
  </ul>
</div>

<div class="slide">
  <h1>Attribute Example</h1>

  <pre><code>package Person;
use Moose;

<span class="highlight">has 'first_name' =&gt; ( is =&gt; 'rw' );</span></code></pre>

</div>

<div class="slide">
  <h1>Methods</h1>

  <ul>
    <li>Nothing fancy here, just Perl subroutines</li>
  </ul>

  <pre><code>package Person;
use Moose;

<span class="highlight">sub greet { ... }</span></code></pre>
</div>

<div class="slide">
  <h1>Roles</h1>

  <ul>
    <li>Classes <strong>do</strong> (or consume) roles</li>
    <li>Similar to mixins and Java interfaces</li>
  </ul>
</div>

<div class="slide">
  <h1>Roles</h1>

  <ul>
    <li>Like classes, can have attributes, methods, do roles</li>
    <li>Roles can require methods</li>
    <li>Roles are composed (flattened) into classes</li>
  </ul>
</div>

<div class="slide">
  <h1>Role Example</h1>

<pre><code>package HasPermissions;
<span class="highlight">use Moose::Role;</span>

has is_admin =&gt; ( is =&gt; 'rw' );</code></pre>
</div>

<div class="slide">
  <h1>Role Example</h1>

  <p>
    And then ...
  </p>
  
<pre><code>package Person;
use Moose;

<span class="highlight">with 'HasPermissions';</span></code></pre>
</div>

<div class="slide">
  <h1>Method Modifiers</h1>

  <ul>
    <li>AKA advice</li>
    <li>&quot;<strong>Before</strong> foo(), do this first&quot;</li>
    <li>&quot;Do this <strong>after</strong> foo()</li>
    <li>&quot;Put this code <strong>around</strong> foo()&quot;</li>
  </ul>
</div>

<div class="slide">
  <h1>Before &amp; After</h1>

<pre><code>before 'foo'
    =&gt; sub { warn 'About to call foo()' };

after  'foo'
    =&gt; sub { warn 'Leaving foo()' };</code></pre>

</div>

<div class="slide">
  <h1>Around</h1>

<pre><code>around 'foo' =&gt; sub {
    my $real_foo = shift;
    my $self     = shift;

    warn 'Just before foo()';
    my @return =
        $self-&gt;$real_foo( @_, bar =&gt; 42 );

    return ( @return, 'modify return values' );
};</code></pre>
</div>

<div class="slide">
  <h1>Type Constraints</h1>

  <ul>
    <li>NOT A FULL-BLOWN TYPE SYSTEM!</li>
    <li>But still darn useful</li>
    <li>Constrain attribute values</li>
    <li>Coerce from other types</li>
  </ul>
</div>

<div class="slide">
  <h1>Type Constraint Example</h1>

<pre><code>package Person;
use Moose;

has 'weight' =&gt; ( is =&gt; 'ro', <span class="highlight">isa =&gt; 'Int'</span> );

# kaboom
Person-&gt;new( weight =&gt; 'fat' );</code></pre>
</div>

<div class="slide">
  <h1>Delegation</h1>

  <ul>
    <li>Attributes can define delegations</li>
    <li>Lets you hide some implementation details</li>
    <li>Fewer objects to chase around</li>
  </ul>
</div>

<div class="slide">
  <h1>Delegation</h1>

<pre><code>package Person;
use Moose;

has 'blog_uri' =&gt; (
    is      =&gt; 'rw',
    isa     =&gt; 'URI',
    <span class="highlight">handles =&gt; { 'blog_hostname' =&gt; 'host' },</span>
);

<span class="highlight">$person->blog_hostname;</span>
# really calls $person->blog_uri->host
</div>

<div class="slide">
  <h1>Constructors</h1>

  <ul>
    <li>Moose creates <code>new()</code> for you</li>
    <li>Provide an optional <code>BUILDARGS()</code> and <code>BUILD()</code></li>
  </ul>
</div>

<div class="slide">
  <h1>Destructors</h1>

  <ul>
    <li>Provide an optional <code>DEMOLISH()</code></li>
  </ul>
</div>

<div class="slide">
  <h1>Moose Meta-API</h1>

  <ul>
    <li>Answers questions like ...
      <ul>
        <li>What methods does this class have?</li>
        <li>What are its parents?</li>
        <li>What attributes does it have (including inherited attributes)?</li>
        <li>What roles does it do?</li>
        <li>Much, much, more</li>
      </ul>
    </li>
  </ul>
</div>

<div class="slide">
  <h1>Moose Meta-API</h1>

  <ul>
    <li>Not just for introspection ...
      <ul>
        <li>Add methods, attributes, roles, etc</li>
        <li>Extend and alter core features</li>
      </ul>
    </li>
  </ul>
</div>

<div class="slide">
  <h1>Why Moose?</h1>

  <ul>
    <li>A quick bit of propoganda ...</li>
  </ul>
</div>

<div class="slide">
  <h1>With Moose</h1>

  <pre><code>package Person;
use Moose;

has last_name =&gt; (
    is  =&gt; 'rw',
    isa =&gt; 'Str',
);</code></pre>
</div>

<div class="slide">
    <h1>Without Moose</h1>

    <pre class="small"><code>package Person;
use strict;
use warnings;
use Carp 'confess';

sub new {
    my $class = shift;
    my %args  = @_;
    my $self  = {};

    if (exists $args{last_name}) {
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
            if ref($args{last_name});
        $self-&gt;{last_nane} = $args{last_name};
    }

    return bless $self, $class;
}

sub last_name {
    my $self = shift;

    if (@_) {
        my $value = shift;
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $value&quot;
            if ref($value);
        $self-&gt;{last_name} = $value;
    }

    return $self-&gt;{last_name};
}</code></pre>

</div>

<div class="slide">
    <h1>Side by side</h1>

    <table class="side-by-side">
        <tr>
          <td>
            <pre><code>package Person;
use Moose;

has last_name =&gt; (
    is  =&gt; 'rw',
    isa =&gt; 'Str',
);</code></pre>
            </td>
            <td>
                <pre class="small"><code>package Person;
use strict;
use warnings;
use Carp 'confess';

sub new {
    my $class = shift;
    my %args  = @_;
    my $self  = {};

    if (exists $args{last_name}) {
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
            if ref($args{last_name});
        $self-&gt;{last_nane} = $args{last_name};
    }

    return bless $self, $class;
}

sub last_name {
    my $self = shift;

    if (@_) {
        my $value = shift;
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $value&quot;
            if ref($value);
        $self-&gt;{last_name} = $value;
    }

    return $self-&gt;{last_name};
}</code></pre>
            </td>
        </tr>
    </table>

</div>

<div class="slide">
    <h1>Side by side</h1>

    <table class="side-by-side">
        <tr>
            <td>
                <pre><code><span class="match-moose">package Person;</span>
use Moose;

has last_name =&gt; (
    is  =&gt; 'rw',
    isa =&gt; 'Str',
);</code></pre>
            </td>
            <td>
                <pre class="small"><code><span class="match-unsweet">package Person;</span>
use strict;
use warnings;
use Carp 'confess';

sub new {
    my $class = shift;
    my %args  = @_;
    my $self  = {};

    if (exists $args{last_name}) {
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
            if ref($args{last_name});
        $self-&gt;{last_nane} = $args{last_name};
    }

    return bless $self, $class;
}

sub last_name {
    my $self = shift;

    if (@_) {
        my $value = shift;
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $value&quot;
            if ref($value);
        $self-&gt;{last_name} = $value;
    }

    return $self-&gt;{last_name};
}</code></pre>
            </td>
        </tr>
    </table>
</div>

<div class="slide">
    <h1>Side by side</h1>

    <table class="side-by-side">
        <tr>
            <td>
                <pre><code>package Person;
<span class="match-moose">use Moose;</span>

has last_name =&gt; (
    is  =&gt; 'rw',
    isa =&gt; 'Str',
);</code></pre>
            </td>
            <td>
                <pre class="small"><code>package Person;
<span class="match-unsweet">use strict;
use warnings;
use Carp 'confess';

sub new {
    my $class = shift;
    my %args  = @_;
    my $self  = {};</span>

    if (exists $args{last_name}) {
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
            if ref($args{last_name});
        $self-&gt;{last_nane} = $args{last_name};
    }

    <span class="match-unsweet">return bless $self, $class;
}</span>

sub last_name {
    my $self = shift;

    if (@_) {
        my $value = shift;
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $value&quot;
            if ref($value);
        $self-&gt;{last_name} = $value;
    }

    return $self-&gt;{last_name};
}</code></pre>
            </td>
        </tr>
    </table>
</div>

<div class="slide">
    <h1>Side by side</h1>

    <table class="side-by-side">
        <tr>
            <td>
                <pre><code>package Person;
use Moose;

<span class="match-moose">has last_name =&gt; (</span>
    is  =&gt; 'rw',
    isa =&gt; 'Str',
<span class="match-moose">);</span></code></pre>
            </td>
            <td>
                <pre class="small"><code>package Person;
use strict;
use warnings;
use Carp 'confess';

sub new {
    my $class = shift;
    my %args  = @_;
    my $self  = {};

    <span class="match-unsweet">if (exists $args{last_name}) {</span>
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
            if ref($args{last_name});
        <span class="match-unsweet">$self-&gt;{last_nane} = $args{last_name};
    }</span>

    return bless $self, $class;
}

sub last_name {
    my $self = shift;

    if (@_) {
        my $value = shift;
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $value&quot;
            if ref($value);
        $self-&gt;{last_name} = $value;
    }

    return $self-&gt;{last_name};
}</code></pre>
            </td>
        </tr>
    </table>
</div>

<div class="slide">
    <h1>Side by side</h1>

    <table class="side-by-side">
        <tr>
            <td>
                <pre><code>package Person;
use Moose;

has last_name =&gt; (
    <span class="match-moose">is  =&gt; 'rw',</span>
    isa =&gt; 'Str',
);</code></pre>
            </td>
            <td>
                <pre class="small"><code>package Person;
use strict;
use warnings;
use Carp 'confess';

sub new {
    my $class = shift;
    my %args  = @_;
    my $self  = {};

    if (exists $args{last_name}) {
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
            if ref($args{last_name});
        $self-&gt;{last_nane} = $args{last_name};
    }

    return bless $self, $class;
}

<span class="match-unsweet">sub last_name {
    my $self = shift;

    if (@_) {
        my $value = shift;</span>
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $value&quot;
            if ref($value);
        <span class="match-unsweet">$self-&gt;{last_name} = $value;
    }

    return $self-&gt;{last_name};
}</span></code></pre>
            </td>
        </tr>
    </table>
</div>

<div class="slide">
    <h1>Side by side</h1>

    <table class="side-by-side">
        <tr>
            <td>
                <pre><code>package Person;
use Moose;

has last_name =&gt; (
    is  =&gt; 'rw',
    <span class="match-moose">isa =&gt; 'Str',</span>
);</code></pre>
            </td>
            <td>
                <pre class="small"><code>package Person;
use strict;
use warnings;
use Carp 'confess';

sub new {
    my $class = shift;
    my %args  = @_;
    my $self  = {};

    if (exists $args{last_name}) {
        <span class="match-unsweet">confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
            if ref($args{last_name});</span>
        $self-&gt;{last_nane} = $args{last_name};
    }

    return bless $self, $class;
}

sub last_name {
    my $self = shift;

    if (@_) {
        my $value = shift;
        <span class="match-unsweet">confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $value&quot;
            if ref($value);</span>
        $self-&gt;{last_name} = $value;
    }

    return $self-&gt;{last_name};
}</code></pre>
            </td>
        </tr>
    </table>
</div>

<div class="slide">
    <h1>Side by side</h1>

    <table class="side-by-side">
        <tr class="incremental">
            <td>5 lines</td>
            <td>21 lines</td>
        </tr>
        <tr class="incremental">
            <td>92 characters</td>
            <td>741 characters</td>
        </tr>
        <tr>
            <td>
                <pre><code>package Person;
use Moose;

has last_name =&gt; (
    is  =&gt; 'rw',
    isa =&gt; 'Str',
);</code></pre>
            </td>
            <td>
                <pre class="small"><code>package Person;
use strict;
use warnings;
use Carp 'confess';

sub new {
    my $class = shift;
    my %args  = @_;
    my $self  = {};

    if (exists $args{last_name}) {
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
            if ref($args{last_name});
        $self-&gt;{last_nane} = $args{last_name};
    }

    return bless $self, $class;
}

sub last_name {
    my $self = shift;

    if (@_) {
        my $value = shift;
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $value&quot;
            if ref($value);
        $self-&gt;{last_name} = $value;
    }

    return $self-&gt;{last_name};
}</code></pre>
            </td>
        </tr>
    </table>
</div>

<div class="slide">
    <h1>Typo?</h1>

    <pre class="small"><code>sub new {
    my $class = shift;
    my %args  = @_;
    my $self  = {};

    if (exists $args{last_name}) {
        confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
                . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
            if ref($args{last_name});
        $self-&gt;{last_nane} = $args{last_name};
    }

    return bless $self, $class;
}</code></pre>
</div>

<div class="slide">
    <h1>Typo?</h1>

    <pre class="small"><code>if (exists $args{last_name}) {
    confess &quot;Attribute (last_name) does not pass the type constraint because: &quot;
            . &quot;Validation failed for 'Str' with value $args{last_name}&quot;
        if ref($args{last_name});
    $self-&gt;{last_nane} = $args{last_name};
}</code></pre>
</div>

<div class="slide">
    <h1>Typo?</h1>

    <code>$self-&gt;{last_nane} = $args{last_name};</code>
</div>

<div class="slide">
    <h1>Typo?</h1>
    <code>$self-&gt;{last_na<span class="highlight">n</span>e}</code>
</div>

<div class="slide">
    <h1>Why Moose?</h1>

    <pre><code>package Person;
use Moose;

has last_name =&gt; (
    is  =&gt; 'rw',
    isa =&gt; 'Str',
);</code></pre>
</div>

<div class="slide fake-slide0">
  <h1>Part 1: Moose Classes</h1>
</div>

<div class="slide">
  <h1>Moose Classes</h1>

  <ul>
    <li>Moose classes are Perl packages which <code>use Moose</code></li>
  </ul>
</div>

<div class="slide">
  <h1>Moose.pm and Your Class</h1>

  <pre><code>package Person;
use Moose;</code></pre>

  <ul>
    <li><code>Moose.pm</code> provides declarative sugar</li>
    <li>Turns on <code>strict</code> and <code>warnings</code></li>
    <li>Creates metaclasses for your class: <code>Person-&gt;meta</code></li>
    <li>Moose classes automatically inherit from <code>Moose::Object</code></li>
  </ul>
</div>

<div class="slide">
  <h1>What <code>Moose::Object</code> Provides</h1>

  <ul>
    <li>Constructor - <code>new()</code></li>
    <li>Calls your <code>BUILDARGS()</code> and/or <code>BUILD()</code></li>
    <li>Calls your <code>DEMOLISH</code> during object destruction</li>
  </ul>
</div>

<div class="slide">
  <h1>extends</h1>

  <ul>
    <li><code>extends</code> is sugar for declaring parent classes</li>
  </ul>

  <pre><code>package Employee;
use Moose;
<span class="highlight">extends 'Person';</span></code></pre>
</div>

<div class="slide">
  <h1>extends</h1>

  <ul>
    <li>Each call to <code>extends</code> <strong>resets</strong> your parents</li>
  </ul>

  <h2 class="wrong">WRONG</h2>

  <pre><code>package EvilEmployee;
use Moose;
extends 'Person';
extends 'Thief';</pre></code>

  <h2 class="right">RIGHT</h2>

  <pre><code>package EvilEmployee;
use Moose;
extends 'Person', 'Thief';</pre></code>
</div>

<div class="slide">
  <h1>Extending un-Moose-y Parents</h1>

  <pre><code>package My::LWP;
use Moose;
extends 'LWP';</pre></code>

  <ul>
    <li>No <code>Moose::Object</code>, so ...
      <ul>
        <li>No attribute-handling <code>new()</code></li>
        <li>No <code>BUILDARGS()</code> or <code>BUILD()</code></li>
        <li>No <code>DEMOLISH()</code></li>
      </ul>
    </li>
    <li>But see <code>MooseX::NonMoose</code> for a workaround</li>
  </ul>
</div>  

<div class="slide">
  <h1><code>overrides</code> and <code>super</code></h1>

  <ul>
    <li><code>overrides</code> is another method modifier</li>
    <li>An alternative to Perl's <code>SUPER::</code></li>
  </ul>
</div>

<div class="slide">
  <h1><code>overrides</code> and <code>super</code></h1>

  <pre><code>package Employee;
use Moose;

<span class="incremental current">extends 'Person';</span>

<span class="incremental">overrides</span> work =&gt; sub {
    my $self = shift;

    die "Pay me first" unless $self-&gt;got_paid;
    <span class="incremental">super();</span>
}<span class="incremental">;</span></code></pre>

<div class="slide">
  <h1>Caveat <code>super</code></h1>

  <ul>
    <li>Mostly like <code>$self-&gt;SUPER::work(@_)</code></li>
    <li><strong>But</strong> cannot change <code>@_</code>!</li>
    <li>Binds the parent's method at compile time</li>
  </ul>
</div>

<div class="slide">
  <h1>Attributes (Part 1)</h1>

  <ul>
    <li><code>has 'foo'</code></li>
    <li>Use <code>is =&gt; 'ro'</code> or <code>is =&gt; 'rw'</code></li>
    <li>Attributes without "is" have no accessors</li>
  </ul>
</div>

<div class="slide">
  <h1>Read-write attributes</h1>

  <pre><code>package Person;
use Moose;

has 'first_name' =&gt; ( <span class="highlight">is =&gt; 'rw'</span> );

my $person =
    Person-&gt;new( first_name =&gt; 'Dave' );

$person-&gt;first_name('Stevan');
print $person-&gt;first_name; # Stevan</code></pre>

</div>

<div class="slide">
  <h1>Read-only attributes</h1>

  <pre><code>package Person;
use Moose;

has 'first_name' =&gt; ( <span class="highlight">is =&gt; 'ro'</span> );

my $person =
    Person-&gt;new( first_name =&gt; 'Dave' );

$person-&gt;first_name('Stevan');
print $person-&gt;first_name; # Dave</code></pre>

</div>

<div class="slide">
  <h1>There is More to Come</h1>

  <ul>
    <li>Attributes have a <em>lot</em> of features</li>
  </ul>
</div>

<div class="slide">
  <h1>Cleaning Up Moose Droppings</h1>

  <pre><code>package Person;
use Moose;

# true
Person->can('extends');</code></pre>

  <ul>
    <li>Not very hygienic</li>
  </ul>
</div>

<div class="slide">
  <h1>Cleaning Up Moose Droppings</h1>

  <pre><code>package Person;
use Moose;

...

no Moose;

# false
Person->can('extends');</code></pre>
</div>

<div class="slide">
  <h1>No Moose</h1>

  <ul>
    <li><code>no Moose</code> at the end of a package is a best practice</li>
    <li>Just do it</li>
  </ul>
</div>

<div class="slide">
  <h1>Immutability</h1>

  <ul>
    <li><span style="font-family: URW Chancery L; font-size: 140%">Stevan's Incantation of Fleet-Footedness</span></li>
  </ul>

  <pre><code>package Person;
use Moose;

<span class="highlight">__PACKAGE__->meta->make_immutable;</span></code></pre>
</div>

<div class="slide">
  <h1>What <code>make_immutable</code> does</h1>

  <ul>
    <li>Magic</li>
    <li>Uses <code>eval</code> to "inline" a constructor</li>
    <li>Memoizes a lot of meta-information</li>
    <li>Makes loading your class slower</li>
    <li>Makes object creation <em>much</em> faster</li>
  </ul>
</div>

<div class="slide">
  <h1>When to Immutabilize?</h1>

  <ul>
    <li><em>Almost</em> always</li>
    <li>Startup time vs execution time</li>
  </ul>
</div>

<div class="slide">
  <h1>Exercises</h1>

  <pre>$ cd exercises
$ perl bin/prove -lv t/00-prereq.t

Missing anything? Install it. (see tarballs/)

# perl bin/prove -lv t/01-classes.t

Iterate til this passes all its tests

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