Moose::Cookbook::Extending::Recipe1 - Providing an alternate base object class
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; Moose->init_meta( @_, base_class => 'MyApp::Object' ); }
Often you find that you want to share some behavior between all your classes. One way to do that is to make a base class and simply add extends 'MyApp::Base' to every class in your application. However, that can get tedious. Instead, you can simply create your Moose-alike module that sets the base object class to MyApp::Base for you.
extends 'MyApp::Base'
MyApp::Base
Then, instead of writing use Moose you can write use MyApp::UseMyBase.
use Moose
use MyApp::UseMyBase
In this particular example, our base class issues some debugging output every time a new object is created, but you can surely think of some more interesting things to do with your own base class.
This all works because of the magic of Moose::Exporter. When we call Moose::Exporter->setup_import_methods( also => 'Moose' ) it builds an import and unimport method for you. The also => 'Moose' bit says that we want to export everything that Moose does.
Moose::Exporter->setup_import_methods( also => 'Moose' )
import
unimport
also => 'Moose'
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.
init_meta
for_caller => $caller
$caller
See the Moose::Exporter docs for more details on its API.
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.
MyApp::UseMyBase
Moose
package Foo; use MyApp::UseMyBase; has 'size' => ( is => 'rw' ); no MyApp::UseMyBase;
Dave Rolsky <autarch@urth.org>
Copyright 2006-2008 by Infinity Interactive, Inc.
http://www.iinteractive.com
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