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Dexter Tad-y > Class-LazyFactory-0.02 > Class::LazyFactory



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Module Version: 0.02   Source  


Class::LazyFactory - Base class factory for lazy-loaded concrete classes


    # factory class 
    package MyHello::Factory;
    use strict;
    use base qw/Class::LazyFactory/;

        namespace   => 'MyHello::Impl',
        constructor => 'new',

    # the base class
    package MyHello::Impl::Abstract;
    use strict;
    use Carp;

    sub new { my $class = shift; return bless({ },$class); }
    sub get_greeting { croak "Unimplemented" }

    # concrete class #1
    package MyHello::Impl::English;
    use strict;
    use base qw/MyHello::Impl::Abstract/;

    sub get_greeting { "hello world" }

    my $greeting = MyHello::Factory->new( "English" );
    print $greeting->get_greeting();


Class::LazyFactory is a base class for factory classes. Concrete classes are lazy loaded, i.e. dynamically require()d, and instances of the concrete classes are constructed.

By using a factory method design pattern, one can provide a consistent interface for constructing a family of classes, without knowing the actual concrete classes in advance.


Class::LazyFactory should be used as the base class for your factory objects. For example:

    package MyHello::Factory;
    use strict;
    use base qw/Class::LazyFactory/;

        namespace   => 'MyHello::Impl',
        constructor => 'new',

MyHello::Factory becomes your factory for constructing objects under the namespace of MyHello::Impl. Concrete classes need not be registered in advance in order to be instantiated. Concrete classes will only be loaded upon first construction.


FACTORY_CLASS->initialize_factory( %params )

This should be called in the factory class inheriting from Class::LazyFactory.

Parameters are as follows:

    namespace       => optional, use of a namespace is strongly recommended.
                       This is the prefix used when resolving the 
                       fully-qualified namespace of the concrete class.
    constructor     => optional, defaults to 'new'.
                       This is the class method that is called when 
                       instantiating a concrete class.
FACTORY_CLASS->new( $concrete_class_name, @params )

Returns an instance of a concrete class. The fully-qualified class name of the concrete class is resolved by concatenating the namespace prefix (see initialize_factory) and $concrete_class_name.

@params is passed to the concrete class constructor.


Factory Design Patterns - Abstract Factory, Factory Method

DBI, DBI::DBD - This module was heavily inspired by DBI; DBI reflects the factory design pattern and that drivers are dynamically loaded from the given DSN string.



Dexter Tad-y, <>


Copyright (C) 2009 by Dexter Tad-y

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.8 or, at your option, any later version of Perl 5 you may have available.

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