@@ -284,10 +297,10 @@ use Moose;
has blog_uri => (
is => 'rw',
isa => 'URI',
- handles => { 'blog_hostname' => 'host' },
+ handles => { 'blog_host' => 'host' },
);
-$person->blog_hostname;
+$person->blog_host;
# really calls $person->blog_uri->host
@@ -341,7 +354,7 @@ has blog_uri => (
@@ -1313,13 +1440,13 @@ use Moose;
use Moose;
with 'IsFragile' =>
- { alias =>
+ { -alias =>
{ break => 'break_bone' },
- exclude => 'break' },
+ -excludes => 'break' },
'CanBreakdance' =>
- { alias =>
- { break => 'break_dance' },
- exclude => 'break' };
+ { -alias =>
+ { break => 'break_it_down' },
+ -excludes => 'break' };
@@ -1331,7 +1458,7 @@ use Moose;
sub break {
my $self = shift;
- $self->break_dance;
+ $self->break_it_down;
if ( rand(1) < 0.5 ) {
$self->break_bone;
}
@@ -1431,7 +1558,7 @@ with 'Killer';
package HasSize;
use Moose::Role;
-requires 'size';
+requires 'size';
package Shirt;
use Moose;
@@ -1492,7 +1619,8 @@ has [ 'left', 'right' ] => (
use Moose::Util qw( apply_all_roles );
my $fragile_person = Person->new( ... );
-apply_all_roles( $fragile_person, 'IsFragile' );
+apply_all_roles( $fragile_person,
+ 'IsFragile' );
- Does not change the
Person class
@@ -1573,14 +1701,2096 @@ requires 'compare';
+
Roles Summary
+
+
+ - Roles can define an interface with
requires
+ - Roles can have state (attributes) and behavior (methods)
+ - Roles can mix interface, state, & behavior
+ - Roles are composed (flattened) into classes
+ - Roles can do other roles
+ - Roles can be used as a type in APIs (must do Comparable)
+
+
+
Questions?
+
+
+
Exercises
-
$ cd exercises
+ # cd exercises
# perl bin/prove -lv t/02-roles.t
Iterate til this passes all its tests
+
+
Part 3: Basic Attributes
+
+
+
+
Attributes Are Huge
+
+
+ - Moose's biggest feature
+ - The target of many MooseX modules
+
+
+
Quick Review
+
+
+ - Declared with
has
+ - Read-only or read-write
+
+
+
package Shirt;
+use Moose;
+
+has 'color' => ( is => 'ro' );
+has 'is_ripped' => ( is => 'rw' );
+
+
Required-ness
+
+
+ - Required means "must be passed to the constructor"
+ - But can be
undef
+
+
+
Required-ness
+
+
package Person;
+use Moose;
+
+has first_name => (
+ is => 'ro',
+ required => 1,
+);
+
+Person->new( first_name => undef ); # ok
+Person->new(); # kaboom
+
+
Default and Builder
+
+
+ - Attributes can have defaults
+ - Simple non-reference scalars (number, string)
+ - Subroutine reference
+ - A builder method
+
+
+
Default
+
+
+ - Can be a non-reference scalar (including
undef)
+
+
+
package Person;
+use Moose;
+
+has bank => (
+ is => 'rw',
+ default => 'Spire FCU',
+);
+
+
Default
+
+
+ - Can be a subroutine reference
+
+
+
package Person;
+use Moose;
+
+has bank => (
+ is => 'rw',
+ default =>
+ sub { Bank->new(
+ name => 'Spire FCU' ) },
+);
+
+
Subroutine Reference Default
+
+
+ - Called as a method on the object
+ - Called anew for each object
+
+
+
Why No Other Reference Types?
+
+
package Person;
+use Moose;
+
+has bank => (
+ is => 'rw',
+ default => Bank->new(
+ name => 'Spire FCU' ),
+);
+
+
+ - Now every person shares the same Bank object!
+
+
+
Defaulting to an Empty Reference
+
+
package Person;
+use Moose;
+
+has packages => (
+ is => 'rw',
+ default => sub { [] },
+);
+
+
What if I Want to Share?
+
+
package Person;
+use Moose;
+
+my $highlander_bank =
+ Bank->new(
+ name => 'Clan MacLeod Trust' );
+
+has bank => (
+ is => 'rw',
+ default => sub { $highlander_bank },
+);
+
+
Builder
+
+
+ - A method name
+ - When called, this method returns the default value
+
+
+
Builder
+
+
package Person;
+use Moose;
+
+has bank => (
+ is => 'rw',
+ builder => '_build_bank',
+);
+
+sub _build_bank {
+ my $self = shift;
+ return Bank->new(
+ name => 'Spire FCU' );
+}
+
+
Default vs Builder
+
+
+ - Use default for simple scalars
+ - Use default to return empty references
+ - Use default for very trivial subroutine references
+ - Use builder for everything else
+
+
+
Builder Bonuses
+
+
+ - Can be overridden and method modified, because it's called by name
+ - Roles can require a builder
+
+
+
Role Requires Builder
+
+
package HasBank;
+use Moose::Role;
+
+requires '_build_bank';
+
+has bank => (
+ is => 'ro',
+ builder => '_build_bank',
+);
+
+
Lazy, Good for Nothin' Attributes
+
+
+ - Normally, defaults are generated during object construction
+ - This can be expensive
+ - We want to default to
$self->size * 2, but attribute initialization order is unpredictable
+ - Use lazy attributes!
+
+
+
The Power of Dynamic Defaults
+
+
package Person;
+use Moose;
+
+has shoe_size => (
+ is => 'ro',
+ required => 'ro',
+);
+
+
The Power of Dynamic Defaults
+
+
has shoes => (
+ is => 'ro',
+ lazy => 1,
+ builder => '_build_shoes',
+);
+
+sub _build_shoes {
+ my $self = shift;
+
+ return Shoes->new(
+ size => $self->shoe_size );
+}
+
+
Lazy is Good
+
+
+ - Lazy defaults are executed when the attribute is read
+ - Can see other object attributes
+ - Still need to watch out for circular laziness
+
+
+
Clearer and Predicate
+
+
+ - Attributes can have a value, including
undef, or not
+ - Can clear the value with a clearer method
+ - Can check for the existence of a value with a predicate method
+ - By default, these methods are not created
+
+
+
Clearer and Predicate
+
+
package Person;
+use Moose;
+
+has account => (
+ is => 'ro',
+ lazy => 1,
+ builder => '_build_account',
+ clearer => '_clear_account',
+ predicate => 'has_account',
+);
+
+
Clearer and Lazy Defaults
+
+
+ - Lazy defaults are good for computed attributes
+ - Clear the attribute when the source data changes
+ - Recalculated at next access
+
+
+
Renaming constructor arguments
+
+
+ - By default, constructor names = attribute names
+ - Use
init_arg to change this
+ - Set
init_arg => undef to make it unconstructable
+
+
+
Some init_arg examples
+
+
package Person;
+use Moose;
+
+has shoe_size => (
+ is => 'ro',
+ init_arg => 'foot_size',
+);
+
+Person->new( shoe_size => 13 );
+
+my $person =
+ Person->new( foot_size => 13 );
+print $person->shoe_size;
+
+
Some init_arg examples
+
+
package Person;
+use Moose;
+
+has shoes => (
+ is => 'ro',
+ init_arg => undef,
+);
+
+Person->new( shoes => Shoes->new );
+
+
Why Set init_arg => undef?
+
+
+ - Use this with a lazy default for attributes-as-cache
+ - Compute the value as needed
+ - Ensure that it is always generated correctly (not set by constructor)
+ - Use triggers or method modifiers (coming soon) to clear the value
+
+
+
Attribute Inheritance
+
+
+ - By default, subclasses inherit attribute as-is
+ - Can change some attribute parameters in subclasses
+
+ - default
+ - builder
+ - required
+ - lazy
+ - others we've not yet covered
+
+
+
+
+
Attribute Inheritance Example
+
+
package Employee;
+use Moose;
+
+extends 'Person';
+
+has '+first_name' => (
+ default => 'Joe',
+);
+
+
Attribute Inheritance Warning
+
+
+ - An attribute is a contract about a class's API
+ - Don't break that contract in a subclass
+ - Especially important in the context of types
+
+
+
Changing Accessor Names
+
+
package Person;
+use Moose;
+
+has first_name => (
+ accessor => 'first_name',
+);
+
+
+ - The long-hand version of
is => 'rw'
+
+
+
Changing Accessor Names
+
+
package Person;
+use Moose;
+
+has first_name => (
+ reader => 'first_name',
+ writer => undef,
+);
+
+
+ - The long-hand version of
is => 'ro'
+
+
+
Changing Accessor Names
+
+
package Person;
+use Moose;
+
+has first_name => (
+ reader => 'get_first_name',
+ writer => 'set_first_name',
+);
+
+
Changing Accessor Names
+
+
package Person;
+use Moose;
+
+has first_name => (
+ is => 'rw',
+ writer => '_first_name',
+);
+
+
+ - Can also mix-and-match
is and explicit names
+
+
+
ETOOMUCHTYPING
+
+
+ MooseX::FollowPBP
get_foo and set_fooMooseX::SemiAffordanceAccessor
foo and set_foo
+
+
ETOOMUCHTYPING
+
+
package Person;
+use Moose;
+use MooseX::SemiAffordanceAccessor;
+
+has first_name => (
+ is => 'rw',
+);
+
+
+ - Creates
first_name and set_first_name
+
+
+
Basic Attributes Summary
+
+
+ - Attributes can be
required
+ - Attributes can have a
default or builder
+ - Attributes with a default or builder can be
lazy
+ - Attributes can have a
clearer and/or predicate
+
+
+
Basic Attributes Summary
+
+
+ - An attribute's constructor name can be changed with
init_arg
+ - A subclass can alter its parents' attributes
+ - Attribute accessor names can be changed
+
+
+
Questions?
+
+
+
+
Exercises
+
+
# cd exercises
+# perl bin/prove -lv \
+ t/03-basic-attributes.t
+
+Iterate til this passes all its tests
+
+
Part 4: Method Modifiers
+
+
+
+
What is a Method Modifier
+
+
+ - Apply to an existing method
+ - ... that comes from a parent class, the current class, or a role
+ - Roles can provide modifiers that are applied at composition time
+
+
+
What Are Method Modifiers For?
+
+
+ - "Inject" behavior
+ - Add behavior to generated methods (accessors, delegations)
+ - Added from a role, can modify existing behavior
+
+
+
Before and After
+
+
+ - Simplest modifiers -
before and after
+ - Guess when they run!
+
+
+
Uses for before
+
+
+
+
package Person;
+use Moose;
+
+before work => sub {
+ my $self = shift;
+ die 'I have no job!'
+ unless $self->has_title;
+};
+
+
Uses for before
+
+
+
+
package Person;
+use Moose;
+
+before work => sub {
+ my $self = shift;
+ return unless $DEBUG;
+
+ warn "Called work on ",
+ $self->full_name,
+ "with the arguments: [@_]\n";
+};
+
+
Uses for after
+
+
+ - Also works for logging/debugging
+ - Post-X side-effects (recording audit info)
+
+
+
package Person;
+use Moose;
+
+after work => sub {
+ my $self = shift;
+ $self->work_count(
+ $self->work_count + 1 );
+};
+
+
Other Uses
+
+
+ - Modifiers are useful for adding behavior to generated methods
+
+
+
More Modifier Examples
+
+
has password => (
+ is => 'rw',
+ clearer => 'clear_password',
+);
+has hashed_password => (
+ is => 'ro',
+ builder => '_build_hashed_password',
+ clearer => '_clear_hashed_password',
+);
+after clear_password => sub {
+ my $self = shift;
+ $self->_clear_hashed_password;
+};
+
+
before and after Limitations
+
+
+ - Cannot alter method parameters
+ - Cannot alter return value
+ - But can throw an exception
+
+
+
The around Modifier
+
+
+ - The big gun
+ - Can alter parameters and/or return values
+ - Can skip calling the wrapped method entirely
+
+
+
The power of around
+
+
around insert => sub {
+ my $orig = shift;
+ my $self = shift;
+
+ $self->_validate_insert(@_);
+
+ my $new_user =
+ $self->$orig(
+ $self->_munge_insert(@_) );
+
+ $new_user->_assign_uri;
+ return $new_user;
+};
+
+
Modifier Order
+
+
+ - Before runs in order from last to first
+ - After runs in order from first to last
+ - Around runs in order from last to first
+
+
+
Modifier Order Illustrated
+
+
+before 2
+ before 1
+ around 2
+ around 1
+ wrapped method
+ around 1
+ around 2
+ after 1
+after 2
+
+
+
Modifiers in Roles
+
+
+ - Roles can use these modifiers
+ - Very powerful!
+
+
+
Modifiers in Roles
+
+
package IsUnreliable;
+use Moose::Role;
+
+requires 'run';
+
+around run => sub {
+ my $orig = shift;
+ my $self = shift;
+
+ return if rand(1) < 0.5;
+
+ return $self->$orig(@_);
+};
+
+
Augment and Inner
+
+
+ - Inverted
super
+ - From least- to most-specific
+ - Like Mason's autohandler feature
+ - Grandparent to parent to child
+ - Not allowed in roles
+
+
+
Augment and Inner
+
+
package Document;
+
+sub xml { '<doc>' . inner() . '</doc>' }
+
+package Report;
+extends 'Document';
+augment xml =>
+ sub { title() . inner() . summary() };
+
+package TPSReport;
+extends 'Report';
+augment xml =>
+ sub { tps_xml() . inner() };
+
+
Augment and Inner
+
+
+ - When we call
$tps->xml ...
+
+ Document->xmlReport->xmlTPSReport->xml
+
+
+
+
Augment and Inner Usage
+
+
+ - Call
inner() to "fill in the blank"
+ - Requires designing for subclassing
+ - Call
inner() in the terminal class, just in case
+
+
+
Method Modifiers Summary
+
+
+ - Use
before and after for ...
+
+ - logging
+ - pre- or post-validation
+ - to add behavior to generated methods
+
+
+ - These two modifiers cannot change parameters or return values
+
+
+
Method Modifiers Summary
+
+
+ - Use
around to ...
+
+ - alter parameters passed to the original method
+ - alter the return value of the original method
+ - not call the original method at all (or call a different method)
+
+
+
+
+
Method Modifiers Summary
+
+
+ - When using modifiers in a role, require the modified method
+ - Use
augment and inner to invert the normal subclassing flow ...
+
+ - Least- to most-specific (parents to children)
+ - Build in "insertability" (stick more stuff in the "middle")
+
+
+ - Always call
inner in the most specific subclass to allow for future extension
+
+
+
Questions?
+
+
+
+
Exercises
+
+
# cd exercises
+# perl bin/prove -lv \
+ t/04-method-modifiers.t
+
+Iterate til this passes all its tests
+
+
Part 5: Types
+
+
+
+
A Type System for Perl
+
+
+ - Sort of ...
+ - Variables are not typed
+ - Attributes can have types
+ - MooseX modules let you define method signatures
+
+
+
Components of a Moose Type
+
+
+ - A type is a name and a constraint
+ - Types have a hierarchy
+ - Constraints are cumulative from parents
+ - Types can have associated coercions
+
+
+
Built-in Type Hierarchy
+
+
+Any
+Item
+ Bool
+ Maybe[`a]
+ Undef
+ Defined
+ Value
+ Str
+ Num
+ Int
+ ClassName
+
+
+
Built-in Type Hierarchy
+
+
+(Item)
+ (Defined)
+ (Value)
+ Ref
+ ScalarRef
+ ArrayRef[`a]
+ HashRef[`a]
+ CodeRef
+ RegexpRef
+ GlobRef
+ FileHandle
+ Object
+
+
+
Bool
+
+
True
+
1
+924.1
+'true'
+{}
+
+
False
+
0
+0.0
+'0'
+undef
+
+
+ - Like Perl's
if ($foo)
+
+
+
Value (and subtypes)
+
+
+ Value is true when ! ref $thingValue and Str are effectively the same, but Str is more expressiveNum is true when a $scalar looks like a number- An overloaded object which numifies does not pass the
Num constraint!
+ - Perl 5's overloading is hopelessly broken
+
+
+
ClassName and RoleName
+
+
+ - A string with a package name
+ - The package must already be loaded
+
+
+
Parameterizable Types
+
+
+ - What does
ArrayRef[`a] mean?
+ s/`a/Int/ (or Str or ...)- When you use it you can write ...
+
+ ArrayRef (== ArrayRef[Item])ArrayRef[Str]ArrayRef[MyTypeName]ArrayRef[HashRef[Maybe[Int]]]
+
+
+
+
Maybe[`a]
+
+
+ - Maybe means either the named type or
undef
+ Maybe[Int] accepts integers or undef
+
+
Type Union
+
+
+ - This or that (or that or ...)
+ Int | ArrayRef[Int]- But use a coercion instead when possible
+ - Or use a
role_type, duck_type, or anything not a union
+ - A union is often a code smell
+
+
+
Making Your Own Types
+
+
use Moose::Util::TypeConstraints;
+
+subtype 'PositiveInt',
+ as 'Int',
+ where { $_ > 0 },
+ message
+ { "The value you provided ($_)"
+ . " was not a positive int." };
+
+has size => (
+ is => 'ro',
+ isa => 'PositiveInt',
+);
+
+
Automatic Types
+
+
+ - Moose creates a type for every Moose class and role
+ - Unknown names are assumed to be classes
+
+
+
Automatic Types
+
+
package Employee;
+use Moose;
+
+has manager => (
+ is => 'rw',
+ isa => 'Employee',
+);
+
+has start_date => (
+ is => 'ro',
+ isa => 'DateTime',
+);
+
+
Subtype Shortcuts - class_type
+
+
use Moose::Util::TypeConstraints;
+class_type 'DateTime';
+
+
+
+
subtype 'DateTime',
+ as 'Object',
+ where { $_->isa('DateTime') },
+ message { ... };
+
+
Subtype Shortcuts - role_type
+
+
use Moose::Util::TypeConstraints;
+role_type 'Printable';
+
+
+
+
subtype 'Printable',
+ as 'Object',
+ where
+ { Moose::Util::does_role(
+ $_, 'Printable' ) },
+ message { ... };
+
+
Subtype Shortcuts - duck_type
+
+
use Moose::Util::TypeConstraints;
+duck_type Car => qw( run break_down );
+
+
+
+
subtype 'Car',
+ as 'Object',
+ where { all { $_->can($_) }
+ qw( run break_down ) },
+ message { ... };
+
+
Subtype Shortcuts - enum
+
+
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 { ... };
+
+
Anonymous Subtypes
+
+
package Person;
+
+my $posint =
+ subtype as 'Int', where { $_ > 0 };
+
+has size => (
+ is => 'ro',
+ isa => $posint,
+);
+
+
+ - Shortcuts have anonymous forms as well
+
+
+
Coercions
+
+
use Moose::Util::TypeConstraints;
+
+subtype 'UCStr',
+ as 'Str',
+ where { ! /[a-z]/ };
+
+
Coercions
+
+
coerce 'UCStr',
+ from 'Str',
+ via { uc };
+
+has shouty_name => (
+ is => 'ro',
+ isa => 'UCStr',
+ coerce => 1,
+);
+
+
Coercion Examples
+
+
subtype 'My::DateTime',
+ as class_type 'DateTime';
+
+coerce 'My::DateTime',
+ from 'HashRef',
+ via { DateTime->new( %{$_} ) };
+
+coerce 'My::DateTime',
+ from 'Int',
+ via { DateTime->from_epoch(
+ epoch => $_ ) };
+
+
+ - Use coercion to inflate a value
+
+
+
Coercion Examples
+
+
coerce 'ArrayRef[Int]',
+ from 'Int',
+ via { [ $_ ] };
+
+
+ - Instead of union -
Int | ArrayRef[Int]
+
+
+
Using Types with Attributes
+
+
package Person;
+
+has height => (
+ is => 'rw',
+ isa => 'Num',
+);
+
+has favorite_numbers => (
+ is => 'rw',
+ isa => 'ArrayRef[Int]',
+ coerce => 1,
+);
+
+
More Droppings
+
+
+ Moose::Util::TypeConstraints also needs cleanup
+
+
package Person;
+
+use Moose;
+use Moose::Util::TypeConstraints;
+
+subtype ...;
+
+no Moose;
+no Moose::Util::TypeConstraints;
+
+
Typed Methods (Low-tech)
+
+
package Person;
+use MooseX::Params::Validate qw( validated_list );
+
+sub work {
+ my $self = shift;
+ my ( $tasks, $can_rest ) =
+ validated_list(
+ \@_,
+ tasks =>
+ { isa => 'ArrayRef[Task]',
+ coerce => 1 },
+ can_rest =>
+ { isa => 'Bool',
+ default => 0 },
+ );
+ ...
+}
+
+
Typed Methods (High-tech)
+
+
package Person;
+
+use MooseX::Method::Signatures;
+
+method work ( ArrayRef[Task] :$tasks,
+ Bool :$can_rest = 0 ) {
+ my $self = shift;
+
+ ...
+}
+
+
Digression: The Type Registry
+
+
+ - Types are actually
Moose::Meta::TypeConstraints objects
+ - Stored in an interpreter-global registry mapping names to objects
+
+
+
Danger!
+
+
+ - Coercions are attached to type objects
+ - Therefore also global
+ - Name conflicts between modules!
+ - Coercion conflicts between modules!
+
+
+
Namespace Fix
+
+
+ - Use some sort of pseudo-namespacing scheme
+ - Never coerce directly to a class name, or to built-in types
+
+
+
Namespace Fix
+
+
use Moose::Util::TypeConstraints;
+subtype 'MyApp::Type::DateTime',
+ as 'DateTime';
+
+coerce 'MyApp::Type::DateTime',
+ from 'HashRef',
+ via { DateTime->new( %{$_} ) }
+
+has creation_date => (
+ is => 'ro',
+ isa => 'MyApp::Type::DateTime',
+ coerce => 1,
+);
+
+
Namespace Fix
+
+
subtype 'MyApp::Type::ArrayOfInt',
+ as 'ArrayRef[Int]';
+
+coerce 'MyApp::Type::ArrayOfInt',
+ from 'Int',
+ via { [ $_ ] };
+
+
Namespace Fix Pros and Cons
+
+
+ - Relatively simple
+ - Already built into Moose
+ - Conflates type and module namespaces
+ - Type names are strings, so typos are easy to make and may be hard to find
+
+
+
MooseX::Types
+
+
package MyApp::Types;
+
+use MooseX::Types
+ -declare => [ qw( ArrayOfInt ) ];
+use MooseX::Types::Moose
+ qw( ArrayRef Int );
+
+subtype ArrayOfInt,
+ as ArrayRef[Int];
+
+coerce ArrayOfInt
+ from Int,
+ via { [ $_ ] };
+
+
MooseX::Types
+
+
package MyApp::Account;
+
+use MyApp::Types qw( ArrayOfInt );
+
+has transaction_history => (
+ is => 'rw',
+ isa => ArrayOfInt,
+);
+
+
MooseX::Types
+
+
+ - Type names are exported functions, catches typos early
+ - Types must be pre-declared
+ - Types are stored with namespaces internally, but you use short names
+ - Import existing Moose types as functions from
MooseX::Types::Moose
+ - Still need string names for things like
ArrayRef['Email::Address']
+
+
+
MooseX::Types Pros and Cons
+
+
+ - Catches typos at compile time
+ - Automatic namespacing
+ - One more thing to install and learn
+ - Every name is typed twice (declared and then defined)
+ - Still stuck with strings when referring to class or role names
+ - Coercion gotcha from earlier still applies to types exported from
MooseX::Types::Moose
+
+
+
Recommendation
+
+
+ - Use
MooseX::Types
+ - Compile time error catching and automatic namespacing are huge wins
+ - Docs from
Moose::Util::TypeConstraints are 98% compatible with MooseX::Types anyway
+ - A function exported by a type library works wherever a type name would
+
+
+
Questions?
+
+
+
+
Exercises
+
+
# cd exercises
+# perl bin/prove -lv t/05-types.t
+
+Iterate til this passes all its tests
+
+
Part 6: Advanced Attributes
+
+
+
+
Weak References
+
+
+ - A weak reference lets you avoid circular references
+ - Weak references do not increase the reference count
+
+
+
Circular Reference Illustrated
+
+
my $foo = {};
+my $bar = { foo => $foo };
+$foo->{bar} = $bar;
+
+
+ - Neither
$foo nor $bar go out of scope
+ (until the program exits)
+
+
+
Weakening Circular References
+
+
use Scalar::Util qw( weaken );
+
+my $foo = {};
+my $bar = { foo => $foo };
+$foo->{bar} = $bar;
+weaken $foo->{bar}
+
+
+ - When
$bar goes out of scope, $foo->{bar} becomes undef
+
+
+
Circular References in Attributes
+
+
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);
+
+
The Fix
+
+
package Person;
+use Moose;
+
+has name => ( is => 'ro' );
+has friend => ( is => 'rw',
+ weak_ref => 1 );
+
+my $alice = Person->new( name => 'Alice' );
+my $bob = Person->new( name => 'Bob' );
+$bob->friend($alice);
+$alice->friend($bob);
+
+
Under the Hood
+
+
+ - A
weak_ref attribute calls weaken ...
+
+ - during object construction
+ - when the attribute is set via a writer
+
+
+
+
+
Triggers
+
+
+ - A code reference run after an attribute is set
+ - Like an
after modifier, but makes intentions clearer
+
+
+
Gross
+
+
after salary_level => {
+ my $self = shift;
+ return unless @_;
+ $self->clear_salary;
+};
+
+
Use a Trigger Instead
+
+
Cleaner
+
+
has salary_level => (
+ is => 'rw',
+ trigger =>
+ sub { $_[0]->clear_salary },
+);
+
+
Delegation
+
+
+ - Attributes can be objects
+ - Delegation transparently calls methods on those objects
+
+
+
Delegation Examples
+
+
package Person;
+
+has lungs => (
+ is => 'ro',
+ isa => 'Lungs',
+ handles => [ 'inhale', 'exhale' ],
+);
+
+
+ - Creates
$person->inhale and ->exhale methods
+ - Internally calls
$person->lungs->inhale
+
+
+
Why Delegation?
+
+
+ - Reduce the number of classes exposed
+ - Re-arrange class internals -
+ turn a method into an attribute with delegation
+ - Provide convenenience methods
+
+
+
Moose's handles Parameter
+
+
+ - Accepts many arguments ...
+
+ - Array reference - list of methods to delegate as-is
+ - Hash reference - map of method names
+ - Regex - delegates all matching methods
+ - Role name - delegates all methods in the role
+ - Sub reference - does something complicated ;)
+
+
+
+
+
Array Reference
+
+
+ - 1-to-1 mapping
+ - Takes each method name and creates a simple delegation from the delegating class to the delegatee attribute
+
+
+
Hash Reference
+
+
+ - Mapping of names in the delegating class to the delegatee class
+
+
+
package Person;
+use Moose;
+has account => (
+ is => 'ro',
+ isa => 'BankAccount',
+ handles => {
+ receive_money => 'deposit',
+ give_money => 'withdraw',
+ },
+);
+
+
Hash Reference Detailed
+
+
handles => {
+ receive_money => 'deposit',
+ give_money => 'withdraw',
+ },
+
+
+ $person->receive_money = $person->account->deposit$person->give_money = $person->account->withdraw
+
+
Regex
+
+
package Person;
+use Moose;
+
+has name => (
+ is => 'ro',
+ isa => 'Name',
+ handles => qr/.*/,
+);
+
+
+ - Creates a delegation for every method in the Name class
+ - Excludes
meta and methods inherited from Moose::Object
+
+
+
Role Name
+
+
package Auditor;
+use Moose::Role;
+sub record_change { ... }
+sub change_history { ... }
+
+package Account;
+use Moose;
+
+has history => (
+ is => 'ro',
+ does => 'Auditor',
+ handles => 'Auditor',
+);
+
+
Role Name Detailed
+
+
+ - Account gets delegate methods for each method in the
Auditor role
+
+ - record_history
+ - change_history
+
+
+
+
+
Native Delegation
+
+
+ - Delegate to unblessed Perl types
+ - Scalar, array or hash ref, etc
+ - Treat Perl types as objects
+ - Still uses
handles
+ - Pretend that native Perl types have methods
+
+
+
Native Delegation - Array(Ref)
+
+
+ - Methods include:
+
+ pushshiftelements - returns all elementscountis_empty- quite a few more
+
+
+
+
+
Native Delegation - Array(Ref)
+
+
package Person;
+use Moose;
+has _favorite_numbers => (
+ traits => [ 'Array' ],
+ is => 'ro',
+ isa => 'ArrayRef[Int]',
+ default => sub { [] },
+ init_arg => undef,
+ handles =>
+ { favorite_numbers => 'elements',
+ add_favorite_number => 'push',
+ },
+);
+
+
Native Delegation - Array(Ref)
+
+
my $person = Person->new();
+
+$person->add_favorite_number(7);
+$person->add_favorite_number(42);
+
+print "$_\n"
+ for $person->favorite_numbers;
+
+# 7
+# 42
+
+
Native Delegation
+
+
+ - Native types are ...
+
+ - Number -
add, mul, ...
+ - String -
append, chop, ...
+ - Counter -
inc, dec, ...
+ - Bool -
set, toggle, ...
+ - Hash -
get, set, ...
+ - Array - already saw it
+ - Code -
execute and execute_method
+
+
+
+
+
Curried Delegation
+
+
+ - A delegation with some preset arguments
+ - Works with object or Native delegation
+
+
+
Curried Delegation
+
+
package Person;
+use Moose;
+has account => (
+ is => 'ro',
+ isa => 'BankAccount',
+ handles => {
+ receive_100 =>
+ [ 'deposit', 100 ]
+ give_100 =>
+ [ 'withdraw', 100 ]
+ },
+);
+
+
Curried Delegation
+
+
$person->receive_100;
+# really is
+$person->account->deposit(100);
+
+
Traits and Metaclasses
+
+
+ - The ultimate in customization
+ - Per attribute metaclasses
+ - Per attribute roles applied to the attribute metaclass
+ - Change the meta-level behavior
+
+
+
Traits and Metaclasses
+
+
+ - The default metaclass is
Moose::Meta::Attribute
+ - Controls accessor generation, defaults, delegation, etc.
+ - Adding a role to this metaclass (or replacing it) allows for infinite customization
+
+
+
Traits and Metaclasses
+
+
+ - Can add/alter/remove an attribute parameter (from
has)
+ - Can change behavior of created attribute
+
+
+
Simple Trait Example
+
+
package Person;
+use Moose;
+use MooseX::LabeledAttributes;
+
+has ssn => (
+ traits => [ 'Labeled' ],
+ is => 'ro',
+ isa => 'Str',
+ label => 'Social Security Number',
+);
+print Person->meta
+ ->get_attribute('ssn')->label;
+
+
Simple Metaclass Example
+
+
package Person;
+use Moose;
+use MooseX::LabeledAttributes;
+
+has ssn => (
+ metaclass =>
+ 'MooseX::Meta::Attribute::Labeled',
+ is => 'ro',
+ isa => 'Str',
+ label => 'Social Security Number',
+);
+print Person->meta
+ ->get_attribute('ssn')->label;
+
+
Traits vs Metaclass
+
+
+ - Can apply any mix of traits to an attribute
+ - But just one metaclass
+ - Traits (aka roles) can cooperate
+ - Metaclasses require you to pick just one
+
+
+
Advanced Attributes Summary
+
+
+ - Use
weak_ref to avoid circular references
+ - Use trigger to do an action post-attribute write
+ - Use delegations to hide "internal" objects
+ - Traits and metaclasses let you extend Moose's core attribute features
+
+
+
Questions?
+
+
+
+
Exercises
+
+
# cd exercises
+# perl bin/prove -lv \
+ t/06-advanced-attributes.t
+
+Iterate til this passes all its tests
+
+
Part 7: Introspection
+
+
+
+
Part 8: A Brief Tour of MooseX
+
+
+
+
Notable MX Modules on CPAN
+
+
+ - Not comprehensive
+ - 152 MooseX distributions on CPAN as of 02/02/2010
+ - Some of them are crap
+
+
+
Already Mentioned Several
+
+
+ MooseX::NonMoose - best solution for subclassing non-Moose parentsMooseX::Declare - real Perl 5 OOMooseX::FollowPBP and MooseX::SemiAffordanceAccessorMooseX::Params::Validate and MooseX::Method::SignaturesMooseX::Types
+
+
MooseX::Declare
+
+
use MooseX::Declare;
+use 5.10.0; # for say
+
+class Person {
+ has greeting =>
+ ( is => 'ro', isa => 'Str' );
+
+ method speak {
+ say $self->greeting;
+ }
+}
+
+
MooseX::Declare
+
+
+ - Still experimental-ish, but seeing more and more use
+ - Not a source filter!
+ - Hooks into the Perl parser rather than filtering all your code
+ - But not supported by
PPI, perltidy, etc. (yet?)
+
+
+
MooseX::StrictConstructor
+
+
+ - By default, unknown constructor arguments are ignored
+ - MX::StrictConstructor turns these into an error
+
+
+
MooseX::StrictConstructor
+
+
package Person;
+
+use Moose;
+use MooseX::StrictConstructor;
+
+has name => ( is => 'ro' );
+
+Person->new
+ ( nane => 'Ringo Shiina' ); # kaboom
+
+
MooseX::Traits
+
+
+ - Combines object construction and role application
+ - Makes it easy to create one-off customized objects
+
+
+
MooseX::Traits
+
+
package MyApp::Thingy;
+use Moose;
+
+with 'MooseX::Traits';
+
+my $thing =
+ MyApp::Thingy->new_with_traits
+ ( traits => [ 'Foo', 'Bar' ],
+ size => 42 );
+
+
MooseX::Getopt
+
+
+ - Makes command-line interface programs easy!
+ - Construct an object from CLI arguments
+
+
+
MooseX::Getopt
+
+
package App::CLI;
+use Moose;
+
+with 'MooseX::Getopt';
+
+has file =>
+ ( is => 'ro', required => 1 );
+has filters =>
+ ( is => 'ro', isa => 'ArrayRef[Str]' );
+
+sub run { ... }
+
+
MooseX::Getopt
+
+
+ - Then call it like this:
+
+
+
#!/usr/bin/perl
+
+use App::CLI;
+
+App::CLI->new_with_options()->run();
+
+
$ myapp-cli \
+ --file foo \
+ --filters compress \
+ --filters sanitize
+
+
MooseX::Clone
+
+
package Person;
+
+use Moose;
+with 'MooseX::Clone';
+
+my $person = Person->new;
+my $clone = $person->clone;
+
+
MooseX::NonMoose
+
+
+ - Highly recommended for subclassing non-Moose parents
+ - Gets all the little annoying details right
+
+
+
MooseX::Role::Parameterized
+
+
package HasCollection;
+use MooseX::Role::Parameterized;
+parameter type => ( isa => 'Str',
+ default => 'Item' );
+role {
+ my $p = shift;
+
+ my $type =
+ 'ArrayRef[' . $p->type() . ']';
+ has collection =>
+ ( is => 'ro',
+ isa => $type );
+};
+
+
MooseX::Role::Parameterized
+
+
package Person;
+
+use Moose;
+with HasCollection => { type => 'Int' };
+
+
Questions?
+
+
+
+
Part 9: Writing Moose Extensions
+
+
+
+
The End
+
+
+
+
- 
+