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Moose::Cookbook::Extending::Recipe3(3) User Contributed Perl Documentation Moose::Cookbook::Extending::Recipe3(3) NAME
Moose::Cookbook::Extending::Recipe3 - Providing an alternate base object class VERSION
version 2.0205 SYNOPSIS
package MyApp::Base; use Moose; extends 'Moose::Object'; before 'new' => sub { warn "Making a new " . $_[0] }; no Moose; package MyApp::UseMyBase; use Moose (); use Moose::Exporter; Moose::Exporter->setup_import_methods( also => 'Moose' ); sub init_meta { shift; return Moose->init_meta( @_, base_class => 'MyApp::Base' ); } DESCRIPTION
A common extension is to provide an alternate base class. One way to do that is to make a "MyApp::base" and add "extends 'MyApp::Base'" to every class in your application. That's pretty tedious. Instead, you can create a Moose-alike module that sets the base object class to "MyApp::Base" for you. Then, instead of writing "use Moose" you can write "use MyApp::UseMyBase". In this particular example, our base class issues some debugging output every time a new object is created, but you can think of some more interesting things to do with your own base class. This uses the magic of Moose::Exporter. When we call "Moose::Exporter->setup_import_methods( also => 'Moose' )" it builds "import" and "unimport" methods for you. The "also => 'Moose'" bit says that we want to export everything that Moose does. The "import" method that gets created will call our "init_meta" method, passing it "for_caller => $caller" as its arguments. The $caller is set to the class that actually imported us in the first place. See the Moose::Exporter docs for more details on its API. USING MyApp::UseMyBase To actually use our new base class, we simply use "MyApp::UseMyBase" instead of "Moose". We get all the Moose sugar plus our new base class. package Foo; use MyApp::UseMyBase; has 'size' => ( is => 'rw' ); no MyApp::UseMyBase; CONCLUSION
This is an awful lot of magic for a simple base class. You will often want to combine a metaclass trait with a base class extension, and that's when this technique is useful. AUTHOR
Stevan Little <stevan@iinteractive.com> COPYRIGHT AND LICENSE
This software is copyright (c) 2011 by Infinity Interactive, Inc.. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself. perl v5.12.5 2011-09-06 Moose::Cookbook::Extending::Recipe3(3)