7 eval 'use Test::Warn 0.11;';
9 diag 'Test::Warn 0.11+ is required for this test';
19 Moose::Cookbook::Extending::Recipe3 - Providing an alternate base object class
26 extends 'Moose::Object';
28 before 'new' => sub { warn "Making a new " . $_[0] };
32 package MyApp::UseMyBase;
36 Moose::Exporter->setup_import_methods( also => 'Moose' );
40 Moose->init_meta( @_, base_class => 'MyApp::Base' );
45 A common extension is to provide an alternate base class. One way to
46 do that is to make a C<MyApp::base> and add C<S<extends
47 'MyApp::Base'>> to every class in your application. That's pretty
48 tedious. Instead, you can create a Moose-alike module that sets the
49 base object class to C<MyApp::Base> for you.
51 Then, instead of writing C<S<use Moose>> you can write C<S<use
54 In this particular example, our base class issues some debugging
55 output every time a new object is created, but you can think of some
56 more interesting things to do with your own base class.
58 This uses the magic of L<Moose::Exporter>. When we call C<<
59 Moose::Exporter->setup_import_methods( also => 'Moose' ) >> it builds
60 C<import> and C<unimport> methods for you. The C<< also => 'Moose' >>
61 bit says that we want to export everything that Moose does.
63 The C<import> method that gets created will call our C<init_meta>
64 method, passing it C<< for_caller => $caller >> as its
65 arguments. The C<$caller> is set to the class that actually imported
66 us in the first place.
68 See the L<Moose::Exporter> docs for more details on its API.
70 =head1 USING MyApp::UseMyBase
72 To actually use our new base class, we simply use C<MyApp::UseMyBase>
73 I<instead> of C<Moose>. We get all the Moose sugar plus our new base
80 has 'size' => ( is => 'rw' );
86 This is an awful lot of magic for a simple base class. You will often
87 want to combine a metaclass trait with a base class extension, and
88 that's when this technique is useful.
92 Dave Rolsky E<lt>autarch@urth.orgE<gt>
94 =head1 COPYRIGHT AND LICENSE
96 Copyright 2006-2009 by Infinity Interactive, Inc.
98 L<http://www.iinteractive.com>
100 This library is free software; you can redistribute it and/or modify
101 it under the same terms as Perl itself.
108 MyApp::UseMyBase->import;
110 has( 'size' => ( is => 'rw' ) );
113 ok( Foo->isa('MyApp::Base'), 'Foo isa MyApp::Base' );
115 ok( Foo->can('size'), 'Foo has a size method' );
119 sub { $foo = Foo->new( size => 2 ) },
121 'got expected warning when calling Foo->new'
124 is( $foo->size(), 2, '$foo->size is 2' );