14 Moose::Cookbook::Extending::Recipe3 - Providing an alternate base object class
21 extends 'Moose::Object';
23 before 'new' => sub { warn "Making a new " . $_[0] };
27 package MyApp::UseMyBase;
31 Moose::Exporter->setup_import_methods( also => 'Moose' );
35 return Moose->init_meta( @_, base_class => 'MyApp::Base' );
40 A common extension is to provide an alternate base class. One way to
41 do that is to make a C<MyApp::base> and add C<S<extends
42 'MyApp::Base'>> to every class in your application. That's pretty
43 tedious. Instead, you can create a Moose-alike module that sets the
44 base object class to C<MyApp::Base> for you.
46 Then, instead of writing C<S<use Moose>> you can write C<S<use
49 In this particular example, our base class issues some debugging
50 output every time a new object is created, but you can think of some
51 more interesting things to do with your own base class.
53 This uses the magic of L<Moose::Exporter>. When we call C<<
54 Moose::Exporter->setup_import_methods( also => 'Moose' ) >> it builds
55 C<import> and C<unimport> methods for you. The C<< also => 'Moose' >>
56 bit says that we want to export everything that Moose does.
58 The C<import> method that gets created will call our C<init_meta>
59 method, passing it C<< for_caller => $caller >> as its
60 arguments. The C<$caller> is set to the class that actually imported
61 us in the first place.
63 See the L<Moose::Exporter> docs for more details on its API.
65 =head1 USING MyApp::UseMyBase
67 To actually use our new base class, we simply use C<MyApp::UseMyBase>
68 I<instead> of C<Moose>. We get all the Moose sugar plus our new base
75 has 'size' => ( is => 'rw' );
81 This is an awful lot of magic for a simple base class. You will often
82 want to combine a metaclass trait with a base class extension, and
83 that's when this technique is useful.
87 Dave Rolsky E<lt>autarch@urth.orgE<gt>
89 =head1 COPYRIGHT AND LICENSE
91 Copyright 2006-2010 by Infinity Interactive, Inc.
93 L<http://www.iinteractive.com>
95 This library is free software; you can redistribute it and/or modify
96 it under the same terms as Perl itself.
103 MyApp::UseMyBase->import;
105 has( 'size' => ( is => 'rw' ) );
108 ok( Foo->isa('MyApp::Base'), 'Foo isa MyApp::Base' );
110 ok( Foo->can('size'), 'Foo has a size method' );
114 sub { $foo = Foo->new( size => 2 ) },
115 qr/^Making a new Foo/,
116 'got expected warning when calling Foo->new'
119 is( $foo->size(), 2, '$foo->size is 2' );