Moose talk at FOSDEM 2011 (Perl devroom)

Moose A postmodern metaclass-based object system for Perl 5

Moose Sawyer X * blogs.perl.org/users/sawyer_x * search.cpan.org/~xsawyerx/ * search.metacpan.org/#/author/XSAWYERX * github.com/xsawyerx

Objects in Perl 5 (a short intro)
A blessed hashref
Manual new() method
No real attributes
bless {}, __PACKAGE__; sub new { my ( $class, @args ) = @_; my $self = { @args }; # params bless $self, $class; return $self; } sub name { my ( $self, $name ) = @_; $name and $self->{'name'} = $name; return $self->{'name'}; }

Why would you want to use Moose? Moose package Person; use strict; use warnings; use Carp qw( confess ); use DateTime; use DateTime::Format::Natural; sub new { my $class = shift; my %p = ref $_[0] ? %{ $_[0] } : @_; exists $p{name} or confess 'name is a required attribute'; $class->_validate_name( $p{name} ); exists $p{birth_date} or confess 'birth_date is a required attribute'; $p{birth_date} = $class->_coerce_birth_date( $p{birth_date} ); $class->_validate_birth_date( $p{birth_date} ); $p{shirt_size} = 'l' unless exists $p{shirt_size}: $class->_validate_shirt_size( $p{shirt_size} ); return bless %p, $class; } sub _validate_name { shift; my $name = shift; local $Carp::CarpLevel = $Carp::CarpLevel + 1; defined $name or confess 'name must be a string'; } Plain old Perl 5 package User; use Email::Valid; use Moose; use Moose::Util::TypeConstraints; extends 'Person'; subtype 'Email' => as 'Str' => where { Email::Valid->address($_) } => message { "$_ is not a valid email address" }; has email_address => ( is => 'rw', isa => 'Email', required => 1, );

Get it?

Defining an object in Moose
use strict
use warnings
An object!
new() method
A pon-.. err.. a moose!
package User; use Moose; 1; You get:

Full-Affordance accessors
' ro ' is also available for read-only attributes!
You can set the getter or setter manually via reader / writer
I'll show more attribute options later on
has name => ( is => 'rw', );

An attribute with type constraint
Lots of types: Str , Int , ArrayRef , HashRef , CodeRef , Regexp
You can combine: ArrayRef[Str] , HashRef[ArrayRef[Int]]
They have inheritance: Int is a Num
Roll your own using subtype
package User; use Moose; has name => ( is => 'rw', isa => 'Str', ); 1;

Methods are the same as before sub method { my $self = shift; ... $self->more(); }

Inheritance is as easy as...
Multiple inheritance is also possible, extends accepts an array
package Punk; use Moose; extends 'Person'; 1; package Child; use Moose; extends qw/ Father Mother /; 1;

Roles are even easier!
Multiple roles are recommend! with accepts an array too
package Punk; use Moose; extends 'Person'; with 'Piercings'; 1; package Punk; use Moose; extends 'Person'; with qw/ Piercings Tattoos /; 1;

More hooks than a coat rack! package User::WinterAware; use Moose; extends 'User'; before leaving => sub { my $self = shift; $self->cold and $self->take_jacket; }; 1;
before
after

More hooks than a coat rack! package User::Secure; use Moose; extends 'User'; around login => sub { my $orig = shift; my $self = shift; $self->security_check and $self->$orig(@_); }; 1;
before
after
around
inner
augment

Back to attributes options... has set => ( is => 'rw', isa => 'Set::Object', default => sub { Set::Object->new }, required => 1, lazy => 1, predicate => 'has_set', clearer => 'clear_set', builder => 'build_set', );

Attribute options default => 'kitteh', # string default => 3, # number default => sub { {} }, # HashRef default => sub { [] }, # ArrayRef default => sub { Object->new }, # an Object etc. etc. (if you need a more elaborate sub, use builder ) default

Attribute options required => 1, # required required => 0, # not required required

Attribute options lazy => 1, # make it lazy Class will not create the slot for this attribute unless it absolutely has to. That is defined by whether it is accessed at all. Wasn't accessed? You don't pay the penalty! :) lazy = good lazy

Attribute options builder => 'build_it', # subroutine name sub build_it { my $self = shift; # not a problem! return Some::Object->new( $self->more_opts, ); } # and, obviously... after build_it => sub { “they will come” }; (a builder sets the value of the attribute) builder

Attribute options clearer => 'clear_it', # subroutine name # you don't need to create the subroutine sub time_machine { my $self = shift; $self->clear_it; # 'it' never happened :) } (a clearer clears the value, as if it never existed) (does not go back to default) clearer

Attribute options predicate => 'has_it', # subroutine name # you don't need to create the subroutine sub try_to_do_it { my $self = shift; $self->has_it && $self->do_it(); } (a predicate checks an attribute value exists) (even false values) (which is good!) predicate

Attribute options lazy_build => 1, # <3 # the same as: lazy => 1, builder => '_build_it', # private clearer => 'clear_it', predicate => 'has_it', ( lazy_build is recommended) lazy_build

Moose
It's beautiful
It's clean
It's stable
It's here to stay
Check it out!
A ton more options
More control
Roles / Traits <3
Extensions OMGZ!
MooseX::SimpleConfig
MooseX::Getopt
MooseX::Declare
MooseX::Types
... sub { goto CPAN; }

Thank you!

Moose talk at FOSDEM 2011 (Perl devroom)

by xSawyer on Feb 08, 2011

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