Paul Seamons
and 1 contributors


AutoRole - Compiletime OR runtime mixin of traits/roles/mixins/your-word-here.

$Id:,v 1.7 2010-07-14 13:25:31 paul Exp $


  use AutoRole Bam => [qw(bar baz bim)];

  use AutoRole
    class   => 'Bam',
    how     => 'autorequire',
    methods => [qw(bar baz bim)];

  use AutoRole
    class   => 'Bam',
    how     => 'compile',
    methods => {
       bar => 1,
       baz => 1,
       bim => 'bim_by_some_other_name',

  use AutoRole
    class   => 'Bam',
    how     => $ENV{'MOD_PERL'} && 'compile', # will default to autorequire if not mod_perl
    method  => 'flimflam',

  use AutoRole
    class   => 'Bam',
    how     => 'autoload', # better if you are using many many mixin methods
    methods => [qw(bar baz bim biz boon bong brim)];

  use AutoRole Bam => [qw(bar baz bim)];
  use AutoRole Bam => autorequire => [qw(bar baz bim)]; # same thing
  use AutoRole Bam => compile     => [qw(bar baz bim)];

  use AutoRole Bam => methods => '*';      # load ALL methods from Bam - at compile time
  use AutoRole Bam => '*';                 # same thing
  use AutoRole 'Bam';                      # same thing
  use AutoRole Bam => {'*' => qr{^bam_}};  # load All methods from Bam that begin with bam_
  use AutoRole Bam => qr{^bam_};           # same thing

  use AutoRole Bam => qr{^(?!bam_)};       # load ALL methods not beginning with bam_


AutoRole is similar to many of the CPAN variants that handle things refered to as Traits, Roles, and Mixins. All of these are fairly similar to each other (in Perl land) though there are subtle nuances. If you use the type how of compile - there is little difference in using AutoRole vs. the CPAN counterparts.

If you use autorequire or autoload however, you save loading the modules until it is necessary to do so. This allows for the creation of "heavy" interfaces with very light frontends. AutoRole allows for only loading extra modules if that role's interface is used.

One more win with roles/mixins/traits is that you can keep your inheritance tree sane (rather than inheriting from a role class).


In many cases the class, how, and method keywords are not needed and the intent can be determined based on the types of parameters. However, you can always pass the parameter names to be specific.


This represents the class you would like to load the roles from.


Can be one of compile, autorequire, or autoload. Default is autorequire if methods are passed, default is compile if no methods are passed or if '*' or qr{} are used for methods.

Option compile will load the module and mix the specified subs/methods in as needed at compile time.

Option autorequire does not load the module at compile time, instead it loads a stub subroutine that will require the module, re-install the real subroutine in place of the stub, and then goto that subroutine (to keep the call stack like it should be).

Option autoload tries to do as little work as possible by only installing an AUTOLOAD subroutine that will load the role methods when called. This is a good option over autorequire if you have a large number of role methods (it gives more of a runtime hit rather than a compiletime hit).

methods or method

Takes an arrayref or hashref of names or a single method name to load. If a hashref is passed, the value may be a different name to alias it to, or an arrayref of names to alias to.

    method => 'foo'

    methods => 'foo'

    methods => ['foo'],

    methods => {foo => 1},

    methods => {foo => 'foo'}

    methods => {foo => 'bar'}           # installs a method called bar rather than foo
    methods => {foo => ['bar', 'baz']}  # installs both bar and baz as rather than foo

You can use the special method name of * to load all of the methods from the sub. The downside to this is it will automatically change to compile time behavior (because it needs to lookup the list of available methods).

    method => '*'

    method => {'*' => 1},

If the methods are specified with a hashref, the value of a * entry may be a regex that will be used to match method names. Note however that this retrieval is only one class deep - so if your role inherits from a base role you will need to load it separately.

    method => {'*' => qr{^debug}} # loads all methods beginning with debug

    methods => {foo => 1,
                '*' => qr{^bar},  # loads foo and any other method beginning with bar

If you use * and other aliases at the same time, the other aliases win.

Since it is a common thing to do - you may also pass simply a qr{} and it will work like {'*' => qr{}}.

    methods => qr{^debug}     # load all methods beginning with debug

    methods => qr{^(?!debug)} # load all methods not beginning with debug

If the how option is compile and no method or methods are passed, it will default to '*'. However if no methods are passed on autorequire or autoload, it will die.


Missing class name

Occurs when the class paramter name is used but no class name follows.

Missing how type

Occurs when the how type is used but no type follows.

How type $how is invalid

Type can only be compile or autorequire.

Method name conflict - ${pkg}::$dest already exists

Occurs if you try and use a method name from a role that is already defined as a method in your class. You can work around this by using the alias feature of the method parameter.

Missing list of methods to load

Occurs if you fail to pass a list of methods during autorequire or autoload. Note that if you don't pass a list under how type compile it will default to '*'.


Paul Seamons


This module may be distributed under the same terms as Perl itself.