John Napiorkowski


Catalyst::ActionSignatures - so you can stop looking at @_


    package MyApp::Controller::Example;

    use Moose;
    use MooseX::MethodAttributes;
    use Catalyst::ActionSignatures;

    extends 'Catalyst::Controller';

    sub test($Req, $Res, Model::A $A, Model::Z $Z) :Local {
        # has $self and $c implicitly
        $Res->body('Look ma, no @_!')

    sub regular_method ($arg1, $arg1) {
      # has $self implicitly



Lets you declare required action dependencies via the method signature.

This subclasses signatures to allow you a more concise approach to creating your controllers. This injects your method signature into the code so you don't need to use @_. You should read signatures to be aware of any limitations.

For actions we automatically inject "$self" and "$c"; for regular methods we inject just "$self".

You should review Catalyst::ActionRole::MethodSignatureDependencyInjection for more on how to construct signatures.

Also Catalyst::ActionSignatures::Rationale may be useful.

Args and Captures

If you specify args and captures in your method signature, you can leave off the associated method attributes (Args($n) and CaptureArgs($n)) IF the method signature is the full specification. In other works instead of:

    sub chain(Model::A $a, Capture $id, $res) :Chained(/) CaptureArgs(1) {
      Test::Most::is $id, 100;
      Test::Most::ok $res->isa('Catalyst::Response');

      sub endchain($res, Arg0 $name) :Chained(chain) Args(1) {
      sub endchain2($res, Arg $first, Arg $last) :Chained(chain) PathPart(endchain) Args(2) {
        $res->body("$first $last");

You can do:

    sub chain(Model::A $a, Capture $id, $res) :Chained(/) {
      Test::Most::is $id, 100;
      Test::Most::ok $res->isa('Catalyst::Response');

      sub endchain($res, Arg0 $name) :Chained(chain)  {
      sub endchain2($res, Arg $first, Arg $last) :Chained(chain) PathPart(endchain)  {
        $res->body("$first $last");

Type Constraints

If you are using a newer Catalyst (greater that 5.90090) you may declare your Args and CaptureArgs typeconstraints via the method signature.

    use Types::Standard qw/Int Str/;

    sub chain(Model::A $a, Capture $id isa Int, $res) :Chained(/) {
      Test::Most::is $id, 100;
      Test::Most::ok $res->isa('Catalyst::Response');

      sub typed0($res, Arg $id) :Chained(chain) PathPart(typed) {

      sub typed1($res, Arg $pid isa Int) :Chained(chain) PathPart(typed) {

NOTE If you declare any type constraints on args or captures, all declared args or captures must have them.

Implicit 'CaptureArgs(0)' and 'Args(0)' in chained actions

If you fail to use an Args or CaptureArgs attributes and you do not declare any captures or args in your chained action method signatures, we automatically add a CaptureArgs(0) attribute. However, since we cannot properly detect the end of a chain, you must still use Args(0) to terminate chains when the last action has no arguments. You may instead use "Chained(link/)" and note the terminal '/' in the chained attribute value to declare a terminal Chain with an implicit Args(0).

    sub another_chain() :Chained(/) { }

      sub another_end($res) :Chained(another_chain/) {

Models and Views

As in the documentation in Catalyst::ActionRole::MethodSignatureDependencyInjection you may declare the required models and views for you action via the method prototype:

    sub myaction(Model::User $user) :Local { ... }

You can also access the default/current model and view:

    sub myaction(Model $current_model) :Local { ... }

You can declare models to be required and conform to a type constraint

    use MyApp::MyTypes 'User';

    sub find_user(Model::User $u isa User requires

Model and View parameters

If your Model or View is a factory that takes parameters, you may supply those from other existing dependencies:

    # like $c->model('ReturnsArg', $id);
    sub from_arg($res, Model::ReturnsArg<Arg $id isa '"Int"'> $model) :Local {
      $res->body("model $model");
      # $id is also available.


Set CATALYST_METHODSIGNATURES_DEBUG to true to get initial debugging output of the generated method signatures and attribute changes. Useful if you are having trouble and want some help to offer a patch!


Catalyst::Action, Catalyst, signatures, Catalyst::ActionRole::MethodSignatureDependencyInjection


John Napiorkowski


Copyright 2015, John Napiorkowski

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