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Moose::Cookbook::Extending::Recipe2.3pm

NAME

Moose::Cookbook::Extending::Recipe2 - Providing a role for the base object class

SYNOPSIS

   package MooseX::Debugging;
 
   use Moose::Exporter;
 
   Moose::Exporter->setup_import_methods(
       base_class_roles => ['MooseX::Debugging::Role::Object'],
   );
 
   package MooseX::Debugging::Role::Object;
 
   use Moose::Role;
 
   after 'BUILDALL' => sub {
       my $self = shift;
 
       warn "Made a new " . ( ref $self ) . " object\n";
   };
 
 

DESCRIPTION

In this example, we provide a role for the base object class that adds some simple debugging output. Every time an object is created, it spits out a warning saying what type of object it was.

Obviously, a real debugging role would do something more interesting, but this recipe is all about how we apply that role.

In this case, with the combination of Moose::Exporter and Moose::Util::MetaRole, we ensure that when a module does "use MooseX::Debugging", it automatically gets the debugging role applied to its base object class.

There are a few pieces of code worth looking at more closely.

   Moose::Exporter->setup_import_methods(
       base_class_roles => ['MooseX::Debugging::Role::Object'],
   );
 
 

This creates an "import" method in the "MooseX::Debugging" package. Since we are not actually exporting anything, we do not pass "setup_import_methods" any parameters related to exports, but we need to have an "import" method to ensure that our "init_meta" method is called. The "init_meta" is created by "setup_import_methods" for us, since we passed the "base_class_roles" parameter. The generated "init_meta" will in turn call Moose::Util::MetaRole::apply_base_class_roles.

AUTHOR

Dave Rolsky <autarch@urth.org>

COPYRIGHT AND LICENSE

Copyright 2009 by Infinity Interactive, Inc.

<http://www.iinteractive.com>

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.