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Sunday, 8 February 2015

Design Patterns in Perl - Factory pattern

Factory class

.../EntityFactory.pm
.../Entity/Asset.pm
.../Entity/Datacentre.pm  etc

type ... the entity type, which corresponds to the database table. Function type2source returns the name of the DBIC ResultSource file in the Result directory ($class). $class is used to load the specialized class (according to the $type) at run time, after which the specialized class object is created and returned;

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package AssetManagerApi2::EntityFactory;

use v5.018;
use utf8;
use open    ':encoding(UTF-8)';
use feature 'unicode_strings';

use FindBin qw($Bin);
use lib "$Bin/../lib";

use AssetManagerApi2::Helper::Entity;

=head3 new

IN: class
    hash of input params for the entity object to be created
    and c and entity type info

=cut

sub new {
    my $class = shift;

    my $entity = AssetManagerApi2::Helper::Entity::type2table(shift); 

    my $path  = "AssetManagerApi2/Entity/$entity.pm";
    $class    = "AssetManagerApi2::Entity::$entity";

    require $path;
    return $class->new(@_);
};


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Specialized classes

Specialized classes are Moose-based and are associated with database table rows represented by DBIx::Class ResultSources.
 
The input to the constructor is a  hashref, containing:
  • Catalyst object and the entity type
  • properties of the DBIC object
      
      example :  { c => $c,  type => $type, id => $dbic->id, name => $dbic->name }

The id, the Catalyst object and the entity type are set up first. Then this information is used by the Moose constructor to set up the rest of the properties through the builder methods.

 

Asset.pm


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package AssetManagerApi2::Entity::Asset;

use Moose;
use namespace::autoclean;

use v5.018;
use utf8;
use open    ':encoding(UTF-8)';
use feature 'unicode_strings';

use AssetManagerApi2::Helper::Entity qw(
                                        create_output_structure
                                     );

my $asset_model = 'AssetManagerDB::Asset';

has 'c'          => (is       => 'ro', 
                     isa      => 'AssetManagerApi2',
                     required =>  1,
                    );

has 'dbic'       => (is       => 'ro', 
                     isa      => 'AssetManagerApi2::Schema::AssetManagerDB::Result::Asset',
                     builder  => '_build_dbic',
                    );

has 'type'       => (is       => 'ro', 
                     isa      => 'Str',
                     lazy     =>  1,
                     builder  => '_build_type',
                     );

has 'id'         => (is       => 'ro', 
                     isa      => 'Int',
                     required =>  1,
                    );

has 'name'       => (is  => 'rw', 
                     isa => 'Str',
                     lazy     =>  1,
                     builder => '_build_name',
                     );

has 'datacentre' => (is  => 'rw', 
                     isa => 'HashRef',
                     lazy     =>  1,
                     builder => '_build_datacentre',
                    );

has 'software'   => (is  => 'ro',               
                     isa => "ArrayRef[HashRef]|ArrayRef",
                     lazy     =>  1,
                     builder => '_build_software',
                    );

=head2 MOOSE METHODS

=cut

=head3 BUILDARGS

The instance is associated with the DBIC object.
    1) Retrieve the DBIC object
    2) Set up some of the Asset object properties before
       Moose constructer takes over

=cut

around BUILDARGS => sub {
    my $orig  = shift;
    my $class = shift;

    my $c    = $_[0]->{c};
    my $dbic = $c->model($asset_model)->find({id => $_[0]->{id}});

    my %props = (
                    c           => $c,
                    id          => $_[0]->{id},
                    type        => 'asset',
                    dbic        => $dbic,
                );

    return $class->$orig(%props);
};
                     
sub _build_type { 
    my ($self) = @_;
}

sub _build_dbic {
    my ($self) = @_;
}
 
sub _build_name {
    my ($self) = @_;

    $self->name($self->dbic->name);
}
 
sub _build_datacentre {
    my ($self) = @_;

    my $c = $self->c;
    my $datacentre_dbic = $self->dbic->datacentre;
    my $datacentre = create_output_structure($c, $datacentre_dbic, 'datacentre');

    $self->datacentre($datacentre);
}
 
sub _build_software {
    my ($self) = @_;

    my $c = $self->c;

    my $self_software_dbic = $self->dbic->softwares;

    my @software = ();
    while (my $package = $self_software_dbic->next) {
        my $software = create_output_structure($c, $package, 'software');
        push @software, $software;
    }

    $self->software(\@software);
}

=head2 PRIVATE HELPER METHODS

=cut

=head2 PUBLIC API METHODS

=cut

sub associate_software {
    my ($self, $props) = @_;

    my $c    = $self->c;
    my $dbic = $self->dbic->find_or_create($props);

    create_output_structure($c, $dbic, 'asset_software');
}

__PACKAGE__->meta->make_immutable;

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