---
name: "Moose::Cookbook::Extending::Debugging_BaseClassRole"
section: "3pm"
platform: "linux"
package: "perl-moose"
version: "2.4001-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/Moose::Cookbook::Extending::Debugging_BaseClassRole"
---

# Moose::Cookbook::Extending::Debugging\_BaseClassRole(3pm)

Providing a role for the base object class

## NAME

Moose::Cookbook::Extending::Debugging\_BaseClassRole - Providing a role for the base object class

## VERSION

version 2.4001

## 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;
  sub BUILD {}
  after BUILD => 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.

```
  sub BUILD {}
  after BUILD => sub {
      ...
  };
```

Due to the way role composition currently works, if the class that a role is composed into contains a `"BUILD"` method, then that will override the `"BUILD"` method in any roles it composes, which is typically not what you want. Using a method modifier on `"BUILD"` avoids this issue, since method modifiers compose together rather than being overridden. Method modifiers require that a method exists in order to wrap, however, so we also provide a stub method to wrap if no `"BUILD"` method exists in the class.

## AUTHORS

- •

  Stevan Little \<stevan@cpan.org\>

- •

  Dave Rolsky \<autarch@urth.org\>

- •

  Jesse Luehrs \<doy@cpan.org\>

- •

  Shawn M Moore \<sartak@cpan.org\>

- •

  יובל קוג'מן (Yuval Kogman) \<nothingmuch@woobling.org\>

- •

  Karen Etheridge \<ether@cpan.org\>

- •

  Florian Ragwitz \<rafl@debian.org\>

- •

  Hans Dieter Pearcey \<hdp@cpan.org\>

- •

  Chris Prather \<chris@prather.org\>

- •

  Matt S Trout \<mstrout@cpan.org\>

## COPYRIGHT AND LICENSE

This software is copyright (c) 2006 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.