in reply to Re: Python OO v Moose
in thread Python OO v Moose

That's a little more compact than I was hoping for to show to non-Perl people, but I may start using it myself. <quote>Also I'll offer a MooX::Struct example for your class. MooX::Struct is a compact builder for simple classes that mainly consist of attributes (not methods).</quote> I was looking for this just last week, but I wanted one of the attributes to be a unique list, so there was a bit of overhead in writing the accessors. 
has 'name' => ( is => 'rw', isa => 'Str', required => 1 );

has 'members' => (
    is  => 'rw',
    isa => 'HashRef',
    default => sub{ {} },
);

sub add_members {
    my ($self, @members) = @_;  
    $self->members()->{$_}++ for (@members); # no duplicates in list
}

sub list_members {
    my $self = shift;
    return keys %{$self->members()};
}

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I use it to create a group with a name and then add members to the list as I pick them out of a database. When I'm finished in the database, I go through all the groups and dump the members list. How would you do that in MooX::Struct and would it be able to modify the members list after instantiation?

Sometimes I can think of 6 impossible LDAP attributes before breakfast.

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Re^3: Python OO v Moose
by tobyink (Canon) on Feb 07, 2013 at 16:43 UTC

    By default, all attributes in MooX::Struct are read-only, but it's easy to make them read-write...

    use MooX::Struct -rw, Person => [qw( $name @addresses )];

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    For your members example, Moose's native traits would probably be helpful. Moo doesn't currently offer anything similar to this, but there is somebody developing such a beast - I believe it will be on CPAN soonish. I'd probably do something along these lines...

    use v5.14;

package Person {
    use Moose;
    use overload q[""] => sub { $_[0]->name }, fallback => 1;
    
    has name => (
        is       => 'ro',
        isa      => 'Str',
        required => 1,
    );
}

package Club {
    use Moose;
    use overload q[""] => sub { $_[0]->name }, fallback => 1;

    has name => (
        is       => 'ro',
        isa      => 'Str',
        required => 1,
    );

    # This is a private attribute. We want people to only
    # manipulate the member list via add_members, etc.
    has _members => (
        traits   => ['Array'],
        is       => 'ro',
        isa      => 'ArrayRef[Person]',
        init_arg => undef,
        default  => sub { [] },
        handles  => {
            add_members   => 'push',
            has_members   => 'count',
            list_members  => 'elements',
            _uniq_members => 'uniq',
        },
    );
    
    # ensure uniqueness
    after add_members => sub {
        my $self = shift;
        @{ $self->_members } = $self->_uniq_members;
    };
}

my $club = Club->new(name => "The Breakfast Club");

$club->add_members(
    Person->new(name => "Allison"), 
    Person->new(name => "Andy"),
    Person->new(name => "Brian"),
    Person->new(name => "Brian"), # duplicate
);

$club->add_members(
    Person->new(name => "Andy"), # duplicate
    Person->new(name => "Claire"),
    Person->new(name => "John"),
);

say for $club->list_members;

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    package Cow { use Moo; has name => (is => 'lazy', default => sub { 'Mooington' }) } say Cow->new->name
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