Moose(X) create my own Collection

ragnaev has asked for the wisdom of the Perl Monks concerning the following question:

Hi PerlMonks, I am a beginner in Moose(X) trying to create a collection of some predefined my types.

use MooseX::Declare

class MyCollection {
  has 'items' => (
    is => 'rw',
    isa => 'HashRef[Object]',
    traits => ['Hash'],
    defaults => sub { {} }
  )

    some..methods
}

use MooseX::Declare;

class Child {
  has 'name' => (
    is => 'rw',
    isa => 'Str'  
  );

  some..methods 
}

use MooseX::Declare;
use MyCollection

class Parent {

  has 'children => (
    is => 'rw',
    isa => 'MyCollection'
  )

  some..methods
}
[download]

So I would like to have in class Parent->children the Collection of child. How to specify that 'children' => isa 'MyCollection[Child]' I try to do so but with no luck. Got and error. Then I try to create a subtype look like

subtype 'MyChildrenCollection' 
=> as 'Collection', 
where => { $_->isa('Child') }
[download]

and use in

has 'children' => (is => 'rw', 'isa' => 'MyChildrenCollection'
[download]

but again no luck. Please dear PerlMontks give me your advice Thanks in advance

Comment on Moose(X) create my own Collection Select or Download Code

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Re: Moose(X) create my own Collection by tobyink (Canon) on Jan 19, 2012 at 09:38 UTC
You don't want to define MyCollection as a class. Define it as a parameterised role instead. IIRC, there is some MooseX::Declare syntactic sugar for parameterised roles, but I can't remember exactly how it goes, and it's undocumented. package MyCollection; use MooseX::Role::Parameterized; parameter type => ( isa => 'ClassName', required => 1, ); parameter attr => ( isa => 'Str', required => 1, ); role { my $p = shift; my ($type, $attr) = ($p->type, $p->attr); has $attr => ( is => 'rw', isa => "HashRef[$type]", traits => ['Hash'], defaults => sub { {} } ); method "summon_$attr" => sub { my $self = shift; foreach my $item (values %{ $self->$attr }) { $item->summon if $item->does('Summonable'); } }; }; # and we'll use MooseX::Declare syntax for the rest... role Summonable { requires 'name'; method summon { say "Come here, ", $self->name; } } class Child with Summonable { has name => ( is => 'ro', isa => 'Str' ); } class Parent { with MyCollection => { type => 'Child', attr => 'children' }; } my $me = Parent->new; $me->children->{isabel} = Child->new(name => 'Isabel'); $me->children->{elliott} = Child->new(name => 'Elliott'); $me->summon_children; [download] The above is untested, and probably has some syntax errors lurking somewhere, but it should give you an idea of how it can be done.	[reply] [d/l]

Replies are listed 'Best First'.

Re: Moose(X) create my own Collection
by tobyink (Canon) on Jan 19, 2012 at 09:38 UTC

You don't want to define MyCollection as a class. Define it as a parameterised role instead. IIRC, there is some MooseX::Declare syntactic sugar for parameterised roles, but I can't remember exactly how it goes, and it's undocumented.

package MyCollection;
use MooseX::Role::Parameterized;

parameter type => (
  isa      => 'ClassName',
  required => 1,
);

parameter attr => (
  isa      => 'Str',
  required => 1,
);

role {
  my $p = shift;
  my ($type, $attr) = ($p->type, $p->attr);

  has $attr => (
    is => 'rw',
    isa => "HashRef[$type]",
    traits => ['Hash'],
    defaults => sub { {} }
    );

  method "summon_$attr" => sub {
    my $self = shift;
    foreach my $item (values %{ $self->$attr }) {
      $item->summon if $item->does('Summonable');
    }
  };
};

# and we'll use MooseX::Declare syntax for the rest...

role Summonable {
  requires 'name';
  method summon {
    say "Come here, ", $self->name;
  }
}

class Child with Summonable {
  has name => ( is => 'ro', isa => 'Str' );
}

class Parent {
  with MyCollection => { type => 'Child', attr => 'children' };
}

my $me = Parent->new;
$me->children->{isabel} = Child->new(name => 'Isabel');
$me->children->{elliott} = Child->new(name => 'Elliott');
$me->summon_children;
[download]

The above is untested, and probably has some syntax errors lurking somewhere, but it should give you an idea of how it can be done.

[reply]
[d/l]