<div class="slide">
<h1>Introduction to Moose</h1>
- <h2>YAPC 2009</h2>
+ <h2>OSCON 2009</h2>
+ <h2><a href="git://git.moose.perl.org/moose-presentations.git"><tt>git://git.moose.perl.org/moose-presentations.git</tt></a></h2>
</div>
<div class="slide">
<h1>Why Moose?</h1>
<ul>
- <li>A quick bit of propoganda ...</li>
+ <li>A quick bit of propaganda ...</li>
</ul>
</div>
</div>
<div class="slide">
+ <h1>BUILDARGS</h1>
+
+ <ul>
+ <li>Takes <code>@_</code>, returns a hash reference of attribute names/value</li>
+ <li>Accepts a hash or hashref; throws otherwise</li>
+ <li>Provide your own for other cases</li>
+ <li><strong>Always</strong> call <code>$class->SUPER::BUILDARGS(@_)</code> as a fallback!</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>BUILDARGS Example</h1>
+
+ <pre><code>package Person;
+use Moose;
+
+sub BUILDARGS {
+ my $class = shift;
+
+ if ( @_ == 1 && ! ref $_[0] ) {
+ <span class="highlight">return { ssn => $_[0] };</span>
+ }
+
+ <span class="highlight">return $class->SUPER::BUILDARGS(@_)</span>;
+}
+
+<span class="highlight">Person->new('123-45-6789')</span></code></pre>
+</div>
+
+<div class="slide">
+ <h1>BUILD</h1>
+
+ <ul>
+ <li>Called after object is created, before <code>new</code> returns</li>
+ <li>Chance to do more complex validation, set complex attributes</li>
+ <li>Called in reverse inheritance order, parents to children</li>
+ <li>Return value is ignored</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>BUILD Example</h1>
+
+ <pre><code>package Person;
+use Moose;
+
+sub BUILD {
+ my $self = shift;
+
+ if ( $self->country_of_residence
+ eq 'USA' ) {
+ die 'All US residents'
+ . ' must have an SSN'
+ unless $self->has_ssn;
+ }
+}</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Object Construction a la Moose</h1>
+
+ <pre><code>Person->new(@_)</code></pre>
+
+ <ol>
+ <li>Calls <code>Person->BUILDARGS(@_)</code> to turn <code>@_</code> into a hashref</li>
+ <li>Blesses a reference</li>
+ <li>Populates attributes based on the hashref from #1</li>
+ <li>Calls <code>$new_object->BUILDALL($constructor_args)</code>
+ <br />... which calls all <code>BUILD</code> methods</li>
+ <li>Returns the object</li>
+ </ol>
+</div>
+
+<div class="slide">
+ <h1>The Object is Opaque</h1>
+
+ <ul>
+ <li>Technically it's a hash reference</li>
+ <li><span class="wrong">If you <em>ever</em> treat it as one <strong>you are doing it wrong!</strong></span></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>DEMOLISH</h1>
+
+ <ul>
+ <li>Like <code>DESTROY</code>, but Moose makes sure all <code>DEMOLISH</code> methods in a hierarchy are called</li>
+ <li>Called in normal inheritance order, children to parents</li>
+ </ul>
+</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>
+ <h2 class="wrong">Wrong</h2>
<pre><code>package EvilEmployee;
use Moose;
extends 'Person';
extends 'Thief';</code></pre>
- <h2 class="right">RIGHT</h2>
+ <h2 class="right">Right</h2>
<pre><code>package EvilEmployee;
use Moose;
</div>
<div class="slide">
- <h1><code>overrides</code> and <code>super</code></h1>
+ <h1><code>override</code> and <code>super</code></h1>
<ul>
- <li><code>overrides</code> is another method modifier</li>
+ <li><code>override</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>
+ <h1><code>override</code> and <code>super</code></h1>
<pre><code>package Employee;
use Moose;
<span class="current incremental">extends 'Person';</span>
-<span class="incremental">overrides</span> work => sub {
+<span class="incremental">override</span> work => sub {
my $self = shift;
die "Pay me first" unless $self->got_paid;
</div>
<div class="slide">
- <h1>Attributes (Part 1)</h1>
+ <h1>Minimal Attributes</h1>
<ul>
<li><code>has 'foo'</code></li>
<ul>
<li><code>no Moose</code> at the end of a package is a best practice</li>
+ <li>Or <code>namespace::clean</code> at the top</li>
<li>Just do it</li>
</ul>
</div>
<li><code>use Moose</code></li>
<li><code>Class->meta</code></li>
<li><code>Moose::Object</code> base class</li>
- <li><code>extends</code>, <code>overrides</code>, and <code>super</code></li>
+ <li><code>extends</code>, <code>override</code>, and <code>super</code></li>
<li>Simple attributes: <code>has</code>, <code>is => 'ro'</code>, & <code>is => 'rw'</code></li>
<li><code>no Moose</code></li>
<li><code>__PACKAGE__->meta->make_immutable</code></li>
<h1>Exercises</h1>
<pre># cd exercises
-$ perl bin/prove -lv t/00-prereq.t
-Missing anything? Install it. (see tarballs/)
+# perl bin/prove -lv t/00-prereq.t
+
+# perl install-moose (if needed)
# perl bin/prove -lv t/01-classes.t
<h1>Conflict Resolution</h1>
<ul>
- <li>The consuming class must resolve the conflict by implementing th emethod</li>
+ <li>The consuming class must resolve the conflict by implementing the method</li>
<li>Can use some combination of method exclusion and aliasing</li>
</ul>
</div>
my $self = shift;
return Shoes->new(
- size => <span class="highlight">$_[0]->shoe_size</span> );
+ size => <span class="highlight">$self->shoe_size</span> );
}</code></pre>
</div>
use Moose;
has first_name => (
- <span class="highlight">reader</span> => 'first_name',
- <span class="highlight">writer</span> => 'first_name',
+ <span class="highlight">accessor</span> => 'first_name',
);</code></pre>
<ul>
has first_name => (
<span class="highlight">reader</span> => 'get_first_name',
- <span class="highlight">writer</span> => 'set_first_name,
+ <span class="highlight">writer</span> => 'set_first_name',
);</code></pre>
</div>
);</code></pre>
<ul>
- <li>Can also mix-and-match</li>
+ <li>Can also mix-and-match <code>is</code> and explicit names</li>
</ul>
</div>
<h1>What is a Method Modifier</h1>
<ul>
- <li>"Iinject" behavior</li>
+ <li>"Inject" behavior</li>
<li>Add behavior to generated methods (accessors, delegations)</li>
<li>Provide roles which modify existing behavior</li>
</ul>
package Report;
extends 'Document';
-<span class="highlight">augment xml</span> => { title() . <span class="highlight">inner()</span> . summary() };
+<span class="highlight">augment xml</span> =>
+ sub { title() . <span class="highlight">inner()</span> . summary() };
package TPSReport;
extends 'Report';
-<span class="highlight">augment xml</span> => { tps_xml() . <span class="highlight">inner()</span> };</code></pre>
+<span class="highlight">augment xml</span> =>
+ sub { tps_xml() . <span class="highlight">inner()</span> };</code></pre>
</div>
<div class="slide">
</div>
<div class="slide">
+ <h1>Method Modifiers Summary</h1>
+
+ <ul>
+ <li>Use <code>before</code> and <code>after</code> for ...
+ <ul>
+ <li>logging</li>
+ <li>pre- or post-validation</li>
+ <li>to add behavior to generated methods</li>
+ </ul>
+ </li>
+ <li>These two modifiers cannot change parameters or return values</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Method Modifiers Summary</h1>
+
+ <ul>
+ <li>Use <code>around</code> to ...
+ <ul>
+ <li>alter parameters passed to the original method</li>
+ <li>alter the return value of the original method</li>
+ <li>not call the original method at all (or call a <em>different</em> method)</li>
+ </ul>
+ </li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Method Modifiers Summary</h1>
+
+ <ul>
+ <li>When using modifiers in a role, require the modified method</li>
+ <li>Use <code>augment</code> and <code>inner</code> to invert the normal subclassing flow ...
+ <ul>
+ <li>Least- to most-specific (parents to children)</li>
+ <li>Build in "insertability" (stick more stuff in the "middle")</li>
+ </ul>
+ </li>
+ <li>Always call <code>inner</code> in the most specific subclass to allow for future extension</li>
+ </ul>
+</div>
+
+<div class="slide">
<h1>Questions?</h1>
</div>
Iterate til this passes all its tests</pre>
</div>
+<div class="slide fake-slide0">
+ <h1>Part 5: Types</h1>
+</div>
+
+<div class="slide">
+ <h1>A Type System for Perl</h1>
+
+ <ul>
+ <li>Sort of ...</li>
+ <li><em>Variables</em> are not typed</li>
+ <li>Attributes can have types</li>
+ <li>MooseX modules let you define method signatures</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Components of a Moose Type</h1>
+
+ <ul>
+ <li>A type is a name and a constraint</li>
+ <li>Types have a hierarchy</li>
+ <li>Constraints are cumulative from parents</li>
+ <li>Types can have associated coercions</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Built-in Type Hierarchy</h1>
+
+ <pre>
+Any
+Item
+ Bool
+ Maybe[`a]
+ Undef
+ Defined
+ Value
+ Num
+ Int
+ Str
+ ClassName
+ RoleName
+</pre>
+</div>
+
+<div class="slide">
+ <h1>Built-in Type Hierarchy</h1>
+
+<pre>
+(Item)
+ (Defined)
+ Ref
+ ScalarRef
+ ArrayRef[`a]
+ HashRef[`a]
+ CodeRef
+ RegexpRef
+ GlobRef
+ FileHandle
+ Object
+</pre>
+</div>
+
+<div class="slide">
+ <h1>Bool</h1>
+
+ <h2>True</h2>
+ <pre><code>1
+924.1
+'true'
+{}</code></pre>
+
+ <h2>False</h2>
+ <pre><code>0
+0.0
+'0'
+undef</code></pre>
+
+ <ul>
+ <li>Like Perl's <code>if ($foo)</code></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Value (and subtypes)</h1>
+
+ <ul>
+ <li><code>Value</code> is true when <code>! ref $thing</code></li>
+ <li><code>Value</code> and <code>Str</code> are effectively the same, but <code>Str</code> is more expressive</li>
+ <li>An overloaded object which numifies does not pass the <code>Num</code> constraint!</li>
+ <li>Perl 5's overloading is hopelessly broken</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>ClassName and RoleName</h1>
+
+ <ul>
+ <li>A string with a package name</li>
+ <li>The package <strong>must already be loaded</strong></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Parameterizable Types</h1>
+
+ <ul>
+ <li>What does <code>ArrayRef[`a]</code> mean?</li>
+ <li><code>s/`a/Int/</code> (or <code>Str</code> or ...)</li>
+ <li>When you use it you can write ...
+ <ul>
+ <li><code>ArrayRef</code> (== <code>ArrayRef[Item]</code>)</li>
+ <li><code>ArrayRef[Str]</code></li>
+ <li><code>ArrayRef[MyTypeName]</code></li>
+ <li><code>ArrayRef[HashRef[Maybe[Int]]]</code></li>
+ </ul>
+ </li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Maybe[`a]</h1>
+
+ <ul>
+ <li>Maybe means either the named type or <code>undef</code></li>
+ <li><code>Maybe[Int]</code> accepts integers or <code>undef</code></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Type Union</h1>
+
+ <ul>
+ <li>This or that (or that or ...)</li>
+ <li><code>Int | ArrayRef[Int]</code></li>
+ <li>But use a coercion instead when possible</li>
+ <li>Or use a <code>role_type</code>, <code>duck_type</code>, or anything not a union</li>
+ <li>A union is often a code smell</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Making Your Own Types</h1>
+
+ <pre><code>use Moose::Util::TypeConstraints;
+
+<span class="incremental current">subtype 'PositiveInt',</span>
+ <span class="incremental">as 'Int',</span>
+ <span class="incremental">where { $_ > 0 },</span>
+ <span class="incremental">message { "The value you provided ($_)"
+ . " was not a positive number." };</span>
+
+has size => (
+ is => 'ro',
+ <span class="incremental">isa => 'PositiveInt',</span>
+);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Automatic Types</h1>
+
+ <ul>
+ <li>Moose creates a type for every Moose class and role</li>
+ <li>Unknown names are assumed to be classes</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Automatic Types</h1>
+
+ <pre><code>package Employee;
+use Moose;
+
+has manager => (
+ is => 'rw',
+ <span class="highlight">isa => 'Employee',</span>
+);
+
+has start_date => (
+ is => 'ro',
+ <span class="highlight">isa => 'DateTime',</span>
+);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Subtype Shortcuts - <code>class_type</code></h1>
+
+ <pre><code>use Moose::Util::TypeConstraints;
+class_type 'DateTime';
+
+subtype 'DateTime',
+ as 'Object',
+ where { $_->isa('DateTime') },
+ message { ... };</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Subtype Shortcuts - <code>role_type</code></h1>
+
+ <pre><code>use Moose::Util::TypeConstraints;
+role_type 'Printable';
+
+subtype 'Printable',
+ as 'Object',
+ where
+ { Moose::Util::does_role(
+ $_, 'Printable' ) },
+ message { ... };</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Subtype Shortcuts - <code>duck_type</code></h1>
+
+ <pre><code>use Moose::Util::TypeConstraints;
+duck_type Car => qw( run break_down );
+
+subtype 'Car',
+ as 'Object',
+ where { all { $_->can($_) }
+ qw( run break_down ) },
+ message { ... };</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Subtype Shortcuts - <code>enum</code></h1>
+
+ <pre><code>use Moose::Util::TypeConstraints;
+enum Color => qw( red blue green ) );
+
+my %ok = map { $_ => 1 } qw( red blue green );
+subtype 'Color'
+ as 'Str',
+ where { $ok{$_} },
+ message { ... };</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Anonymous Subtypes</h1>
+
+ <pre><code>package Person;
+
+<span class="highlight">my $posint =
+ subtype as 'Int', where { $_ > 0 };</span>
+
+has size => (
+ is => 'ro',
+ <span class="highlight">isa => $posint,</span>
+);</code></pre>
+
+ <ul>
+ <li>Shortcuts have anonymous forms as well</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Coercions</h1>
+
+ <pre><code>use Moose::Util::TypeConstraints;
+
+subtype 'UCStr',
+ as 'Str',
+ where { ! /[a-z]/ };
+
+<span class="incremental current">coerce 'UCStr',</span>
+ <span class="incremental">from 'Str',</span>
+ <span class="incremental">via { uc };</span>
+
+has shouty_name => (
+ is => 'ro',
+ isa => 'UCStr',
+ <span class="incremental">coerce => 1,</span>
+);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Coercion Examples</h1>
+
+ <pre><code>subtype 'My::DateTime',
+ as class_type 'DateTime';
+
+coerce 'My::DateTime',
+ from 'HashRef',
+ via { DateTime->new( %{$_} ) };
+
+coerce 'My::DateTime',
+ from 'Int',
+ via { DateTime->from_epoch(
+ epoch => $_ ) };</code></pre>
+
+ <ul>
+ <li>Use coercion to inflate a value</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Coercion Examples</h1>
+
+ <pre><code>coerce 'ArrayRef[Int]',
+ from 'Int',
+ via { [ $_ ] };</code></pre>
+
+ <ul>
+ <li>Coerce instead of a union like <code style="white-space: nowrap">Int | ArrayRef[Int]</code></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Using Types with Attributes</h1>
+
+ <pre><code>package Person;
+
+use Moose::Util::TypeConstraints;
+
+has height => (
+ is => 'rw',
+ <span class="highlight">isa => 'Num',</span>
+);
+
+has favorite_numbers => (
+ is => 'rw',
+ <span class="highlight">isa => 'ArrayRef[Int]',
+ coerce => 1,</span>
+);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>More Droppings</h1>
+
+ <ul>
+ <li><code>Moose::Util::TypeConstraint</code> also needs cleanup</li>
+ </ul>
+
+ <pre><code>package Person;
+
+use Moose;
+use Moose::Util::TypeConstraints;
+
+subtype ...;
+
+no Moose;
+<span class="highlight">no Moose::Util::TypeConstraints;</span></code></pre>
+</div>
+
+<div class="slide">
+ <h1>Typed Methods (Low-tech)</h1>
+
+ <pre class="medium"><code>package Person;
+<span class="highlight">use MooseX::Params::Validate qw( validated_list );</span>
+
+sub work {
+ my $self = shift;
+ <span class="highlight">my ( $tasks, $can_rest ) =
+ validated_list(
+ \@_,
+ tasks =>
+ { isa => 'ArrayRef[Task]',
+ coerce =>1 },
+ can_rest =>
+ { isa => 'Bool',
+ default => 0 },
+ );</span>
+
+ ...
+}</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Typed Methods (High-tech)</h1>
+
+ <pre class="medium"><code>package Person;
+
+<span class="highlight">use MooseX::Method::Signatures;</span>
+
+<span class="highlight">method work ( ArrayRef[Task] :$tasks,
+ Bool :$can_rest = 0 )</span> {
+ my $self = shift;
+
+ ...
+}</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Digression: The Type Registry</h1>
+
+ <ul>
+ <li>Types are actually <code>Moose::Meta::TypeConstraint</code> <em>objects</em></li>
+ <li>Stored in an interpreter-global registry mapping names to objects</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Danger!</h1>
+
+ <ul>
+ <li>Coercions are attached to type objects</li>
+ <li>Therefore also global</li>
+ <li>Name conflicts between modules!</li>
+ <li>Coercion conflicts between modules!</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Namespace Fix</h1>
+
+ <ul>
+ <li>Use some sort of pseudo-namespacing scheme</li>
+ <li>Never coerce directly to a class name, or <em>to</em> built-in types</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Namespace Fix</h1>
+
+ <pre><code>use Moose::Util::TypeConstraints;
+
+subtype <span class="highlight">'MyApp::Type::DateTime',</span>
+ as 'DateTime';
+
+<span class="highlight">coerce 'MyApp::Type::DateTime',</span>
+ from 'HashRef',
+ via { DateTime->new( %{$_} ) }
+
+has creation_date => (
+ is => 'ro',
+ <span class="highlight">isa => 'MyApp::Type::DateTime',</span>
+ coerce => 1,
+);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Namespace Fix</h1>
+
+ <pre><code>subtype 'MyApp::Type::ArrayOfInt',
+ as 'ArrayRef[Int]';
+
+coerce 'MyApp::Type::ArrayOfInt',
+ from 'Int',
+ via { [ $_ ] };</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Namespace Fix Pros and Cons</h1>
+
+ <ul>
+ <li><span class="right">Relatively simple</span></li>
+ <li><span class="right">Already built into Moose</span></li>
+ <li><span class="wrong">Conflates type and module namespaces</span></li>
+ <li><span class="wrong">Type names are strings, so typos are easy to make and may be hard to find</span></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>MooseX::Types</h1>
+
+ <pre><code>package MyApp::Types;
+
+use MooseX::Types
+ <span class="highlight">-declare => [ qw( ArrayOfInt ) ]</span>;
+use MooseX::Types::Moose
+ qw( ArrayRef Int );
+
+subtype <span class="highlight">ArrayOfInt</span>,
+ as ArrayRef[Int];
+
+coerce <span class="highlight">ArrayOfInt</span>
+ from Int,
+ via { [ $_ ] };</code></pre>
+</div>
+
+<div class="slide">
+ <h1>MooseX::Types</h1>
+
+ <pre><code>package MyApp::Account;
+
+use MyApp::Types qw( ArrayOfInt );
+
+has transaction_history => (
+ is => 'rw',
+ isa => ArrayOfInt,
+);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>MooseX::Types</h1>
+
+ <ul>
+ <li>Type names are exported functions, catches typos early</li>
+ <li>Types must be pre-declared</li>
+ <li>Types are stored with namespaces internally, but externally are short</li>
+ <li>Import existing Moose types as functions from <code>MooseX::Types::Moose</code></li>
+ <li>Still need string names for things like <code>ArrayRef['Email::Address']</code></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>MooseX::Types Pros and Cons</h1>
+
+ <ul>
+ <li><span class="right">Catches typos at compile time</span></li>
+ <li><span class="right">Automatic namespacing</span></li>
+ <li><span class="wrong">One more thing to install and learn</span></li>
+ <li><span class="wrong">Every name gets types twice (declared and then defined)</span></li>
+ <li><span class="wrong">Still stuck with strings when referring to class or role names</span></li>
+ <li><span class="wrong">Coercion gotcha from earlier still applies to types exported from <code>MooseX::Types::Moose</code></span></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Recommendation</h1>
+
+ <ul>
+ <li>Use <code>MooseX::Types</code></li>
+ <li>Compile time error catching and automatic namespacing are huge wins</li>
+ <li>Docs from <code>Moose::Util::TypeConstraints</code> are 98% compatible with <code>MooseX::Types</code> anyway</li>
+ <li>A function exported by a type library works wherever a type name would</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Questions?</h1>
+</div>
+
+<div class="slide">
+ <h1>Exercises</h1>
+
+ <pre># cd exercises
+# perl bin/prove -lv t/05-types.t
+
+Iterate til this passes all its tests</pre>
+</div>
+
+<div class="slide fake-slide0">
+ <h1>Part 6: Advanced Attributes</h1>
+</div>
+
+<div class="slide">
+ <h1>Weak References</h1>
+
+ <ul>
+ <li>A weak reference lets you avoid circular references</li>
+ <li>Weak references do not increase the reference count</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Circular Reference Illustrated</h1>
+
+ <pre><code>my $foo = {};
+my $bar = { foo => $foo };
+$foo->{bar} = $bar;</code></pre>
+
+ <ul>
+ <li>Neither <code>$foo</code> nor <code>$bar</code> go out of scope<br />
+ (until the program exits)</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Weakening Circular References</h1>
+
+ <pre><code>use Scalar::Util qw( weaken );
+
+my $foo = {};
+my $bar = { foo => $foo };
+$foo->{bar} = $bar;
+weaken $foo->{bar}</code></pre>
+
+ <ul>
+ <li>When <code>$bar</code> goes out of scope, <code>$foo->{bar}</code> becomes <code>undef</code></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Circular References in Attributes</h1>
+
+ <pre><code>package Person;
+use Moose;
+
+has name => ( is => 'ro' );
+has friend => ( is => 'rw' );
+
+my $alice = Person->new( name => 'Alice' );
+my $bob = Person->new( name => 'Bob' );
+$bob->friend($alice);
+$alice->friend($bob);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>The Fix</h1>
+
+ <pre><code>package Person;
+use Moose;
+
+has name => ( is => 'ro' );
+has friend => ( is => 'rw', <span class="highlight">weak_ref => 1</span> );
+
+my $alice = Person->new( name => 'Alice' );
+my $bob = Person->new( name => 'Bob' );
+$bob->friend($alice);
+$alice->friend($bob);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Under the Hood</h1>
+
+ <ul>
+ <li>A <code>weak_ref</code> attribute calls <code>weaken</code> ...
+ <ul>
+ <li>during object construction</li>
+ <li>when the attribute is set via a writer</li>
+ </ul>
+ </li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Triggers</h1>
+
+ <ul>
+ <li>A code reference run after an attribute is <em>set</em></li>
+ <li>Like an <code>after</code> modifier, but makes intentions clearer</li>
+ </ul>
+
+ <h2 class="wrong">Gross</h2>
+
+ <pre><code>after salary_level => {
+ my $self = shift;
+ return unless @_;
+ $self->clear_salary;
+};</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Use a Trigger Instead</h1>
+
+ <h2 class="right">Cleaner</h2>
+
+ <pre><code>has salary_level => (
+ is => 'rw',
+ trigger => sub { $_[0]->clear_salary },
+);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Delegation</h1>
+
+ <ul>
+ <li>Attributes can be objects</li>
+ <li>Delegation transparently calls methods on those objects</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Delegation Examples</h1>
+
+ <pre><code>package Person;
+
+has lungs => (
+ is => 'ro',
+ isa => 'Lungs',
+ <span class="highlight">handles => [ 'inhale', 'exhale' ],</span>
+);</code></pre>
+
+ <ul>
+ <li>Creates <code>$person->inhale</code> and <code>->exhale</code> methods</li>
+ <li>Internally calls <code>$person->lungs->inhale</code></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Why Delegation?</h1>
+
+ <ul>
+ <li>Reduce the number of classes exposed</li>
+ <li>Re-arrange class internals -<br />
+ turn a method into an attribute with delegation</li>
+ <li>Provide convenenience methods</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Moose's <code>handles</code> Parameter</h1>
+
+ <ul>
+ <li>Accepts many arguments ...
+ <ul>
+ <li>Array reference - list of methods to delegate as-is</li>
+ <li>Hash reference - map of method names</li>
+ <li>Regex - delegates all matching methods</li>
+ <li>Role name - delegates all methods in the role</li>
+ <li>Sub reference - does something complicated ;)</li>
+ </ul>
+ </li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Array Reference</h1>
+
+ <ul>
+ <li>Takes each method name and creates a simple delegation from the delegating class to the delegatee attribute</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Hash Reference</h1>
+
+ <ul>
+ <li>Mapping of names in the delegating class to the delegatee class</li>
+ </ul>
+
+ <pre><code>package Person;
+use Moose;
+
+has account => (
+ is => 'ro',
+ isa => 'BankAccount',
+ <span class="highlight">handles => {
+ receive_money => 'deposit',
+ give_money => 'withdraw',
+ },</span>
+);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Hash Reference Detailed</h1>
+
+ <pre><code> handles => {
+ receive_money => 'deposit',
+ give_money => 'withdraw',
+ },</code></pre>
+
+ <ul>
+ <li><code>$person->receive_money</code> = <code>$person->account->deposit</code></li>
+ <li><code>$person->give_money</code> = <code>$person->account->withdraw</code></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Regex</h1>
+
+ <pre><code>package Person;
+use Moose;
+
+has name => (
+ is => 'ro',
+ isa => 'Name',
+ handles => qr/.*/,
+);</code></pre>
+
+ <ul>
+ <li>Creates a delegation for every method in the Name class</li>
+ <li>Excludes <code>meta</code> and methods inherited from <code>Moose::Object</code></li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Role Name</h1>
+
+ <pre><code>package Auditor;
+use Moose::Role;
+
+sub record_change { ... }
+sub change_history { ... }
+
+package Account;
+use Moose;
+
+has history => (
+ is => 'ro',
+ does => 'Auditor',
+ <span class="highlight">handles => 'Auditor',</span>
+);</code></pre>
+</div>
+
+<div class="slide">
+ <h1>Role Name Detailed</h1>
+
+ <ul>
+ <li>Account gets delegate methods for each method in the <code>Auditor</code> role
+ <ul>
+ <li>record_history</li>
+ <li>change_history</li>
+ </ul>
+ </li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Traits and Metaclasses</h1>
+
+ <ul>
+ <li>The ultimate in customization</li>
+ <li>Per attribute metaclasses</li>
+ <li>Per attribute roles applied to the attribute metaclass</li>
+ <li>Change the meta-level behavior</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Traits and Metaclasses</h1>
+
+ <ul>
+ <li>The default metaclass is <code>Moose::Meta::Attribute</code></li>
+ <li>Controls accessor generation, defaults, delegation, etc.</li>
+ <li>Adding a role to this metaclass (or replacing it) allows for infinite customization</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Traits and Metaclasses</h1>
+
+ <ul>
+ <li>Can add/alter/remove attribute parameter (from <code>has</code>)</li>
+ <li>Can change behavior of created attribute</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Simple Trait Example</h1>
+
+ <pre><code>package Person;
+use Moose;
+use MooseX::LabeledAttributes;
+
+has ssn => (
+ <span class="highlight">traits => [ 'Labeled' ],</span>
+ is => 'ro',
+ isa => 'Str',
+ <span class="highlight">label => 'Social Security Number',</span>
+);
+
+print <span class="highlight">Person->meta
+ ->get_attribute('ssn')->label;</span></code></pre>
+</div>
+
+<div class="slide">
+ <h1>Simple Metaclass Example</h1>
+
+ <pre><code>package Person;
+use Moose;
+use MooseX::LabeledAttributes;
+
+has ssn => (
+ <span class="highlight">metaclass =>
+ 'MooseX::Meta::Attribute::Labeled',</span>
+ is => 'ro',
+ isa => 'Str',
+ <span class="highlight">label => 'Social Security Number',</span>
+);
+
+print <span class="highlight">Person->meta
+ ->get_attribute('ssn')->label;</span></code></pre>
+</div>
+
+<div class="slide">
+ <h1>Traits vs Metaclass</h1>
+
+ <ul>
+ <li>Can apply any mix of traits to an attribute</li>
+ <li>But just one metaclass</li>
+ <li>Traits (aka roles) can cooperate</li>
+ <li>Metaclasses require you to pick just one</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Advanced Attributes Summary</h1>
+
+ <ul>
+ <li>Use <code>weak_ref</code> to avoid circular references</li>
+ <li>Use trigger to do an action post-attribute write</li>
+ <li>Use delegations to hide "internal" objects</li>
+ <li>Traits and metaclasses let you extend Moose's core attribute features</li>
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Questions?</h1>
+</div>
+
+<div class="slide">
+ <h1>Exercises</h1>
+
+ <pre># cd exercises
+# perl bin/prove -lv t/06-advanced-attributes.t
+
+Iterate til this passes all its tests</pre>
+</div>
+
+<div class="slide fake-slide0">
+ <h1>Part 7: Introspection</h1>
+</div>
+
+<div class="slide fake-slide0">
+ <h1>Part 8: A Tour of MooseX</h1>
+</div>
+
+<div class="slide fake-slide0">
+ <h1>Part 9: Writing Moose Extensions</h1>
+</div>
+
+<div class="slide fake-slide0">
+ <h1>The End</h1>
+</div>
+
+<div class="slide">
+ <h1>More Information</h1>
+
+ <ul>
+ <li><a href="http://moose.perl.org/">http://moose.perl.org/</a></li>
+ <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>
+ <li><a href="irc://irc.perl.org/#moose">irc://irc.perl.org/#moose</a></li>
+ <li>mailing list - <a href="mailto:moose@perl.org">moose@perl.org</a></li>
+ <li>Slides and exercises are in Moose's git repo:
+ <br />
+ <span style="white-space: nowrap">git://jules.scsys.co.uk/gitmo/moose-presentations</span></li>
+ </ul>
+</div>
+
</div>
</body>
</html>
projects / gitmo/moose-presentations.git / blobdiff