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John Napiorkowski

NAME

Catalyst::Plugin::InjectionHelpers - Enhance Catalyst Component Injection

SYNOPSIS

Use the plugin in your application class:

    package MyApp;
    use Catalyst 'InjectionHelpers';

    MyApp->inject_components(
      'Model::SingletonA' => {
        from_class=>'MyApp::Singleton', 
        adaptor=>'Application', 
        roles=>['MyApp::Role::Foo'],
        method=>'new',
      },
      'Model::SingletonB' => {
        from_class=>'MyApp::Singleton', 
        adaptor=>'Application', 
        method=>sub {
          my ($adaptor_instance, $from_class, $app, %args) = @_;
          return $class->new(aaa=>$args{arg});
        },
      },
    );

    MyApp->config(
      'Model::SingletonA' => { aaa=>100 },
      'Model::SingletonB' => { arg=>300 },
    );

    MyApp->setup;

Alternatively you can use the 'config' only approach which may be useful if you have configuration file overlays that change how injections work on a per environment basis:

    package MyApp;
    use Catalyst 'InjectionHelpers';

    MyApp->config(
      'Model::SingletonA' => {
        -inject => {
          from_class=>'MyApp::Singleton', 
          adaptor=>'Application', 
          roles=>['MyApp::Role::Foo'],
          method=>'new',
        },
        aaa => 100,
      },
      'Model::SingletonB' => {
        -inject => {
          from_class=>'MyApp::Singleton', 
          adaptor=>'Application', 
          method=>sub {
            my ($adaptor_instance, $from_class, $app, %args) = @_;
            return $class->new(aaa=>$args{arg});
        },
        arg => 300,
      },
    );

    MyApp->setup;

DESCRIPTION

This plugin enhances the build in component injection features of Catalyst (since v5.90090) to make it easy to bring non Catalyst::Component classes into your application. You may consider using this for what you often used Catalyst::Model::Adaptor in the past for (although there is no reason to stop using that if you are doing so, its not a 'broken' approach, but for the very simple cases this might suffice and allow you to reduce the number of nearly empty 'boilerplate' classes in your application.

You should be familiar with how component injection works in newer versions of Catalyst (v5.90090+).

USAGE

    MyApp->inject_components($model_name => \%args);

Where $model_name is the name of the component as it is in your Catalyst application (ie 'Model::User', 'View::HTML', 'Controller::Static') and %args are key /values as described below:

from_class

This is the full namespace of the class you are adapting to use as a Catalyst component. Example 'MyApp::Class'.

from_code

This is a codereference that generates your component instance. Used when you don't have a class you wish to adapt (handy for prototyping or small components).

    MyApp->inject_components(
      'Model::Foo' => {
        from_code => sub {
          my ($adaptor_instance, $coderef, $app, %args) = @_;
          return $XX;
        },
        adaptor => 'Factory',
      },
    );

The second arguement is a reference to the orginal 'from_code' coderef (useful for when you need to do recursion.)

If you use this you should not define the 'method' key or the 'roles' key (below).

roles

A list of Moose::Roless that will be composed into the 'from_class' prior to creating an instance of that class.

method

Either a string or a coderef. If left empty this defaults to 'new'.

The name of the method used to create the adapted class instance. Generally this is 'new'. If you have complex instantiation requirements you may instead use a coderef. If so, your coderef will receive four arguments. The first is the adaptor instance. The second is the name of the from_class. The third is either the application or context, depending on the type adaptor. The forth is a hash of arguments which merges the global configuration for the named component along with any arguments passed in the request for the component (this only makes sense for non application scoped models, btw).

Example:

    MyApp->inject_components(
      'Model::Foo' => {
        from_class => 'Foo',
        method => sub {
          my ($adaptor_instance, $from_class, $app_or_ctx, %args) = @_;
        },
        adaptor => 'Factory',
      },
    );

Argument details:

$adaptor_instance

Reference to the adaptor object. Useful if you made your own adaptor and wish to access methods and attributes from it. See Catalyst::ModelRole::InjectionHelpers and the specific adaptor for more information.

$from_class

The name of the class you set in the 'from_class' parameter.

$app_or_ctx

Either your application class or a reference to the current context, depending on how the adaptore is scoped (PerRequest and Factory get $ctx).

%args

A Hash of the configuration parameters from your application configuration. If the adaptor is context/request scoped, also combines any arguments included in the call for the component. for example:

    package MyApp;

    use Catalyst;

    MyApp->inject_components( 'Model::Foo' => { from_class=>"Foo", adaptor=>'Factory' });
    MyApp->config( 'Model::Foo' => { aaa => 111 } )
    MyApp->setup;

If in an action you say:

    my $model = $c->model('Foo', bbb=>222);

Then %args would be:

    (aaa=>111, bbb=>222);

adaptor

The adaptor used to bring your 'from_class' into Catalyst. Out of the box there are three adaptors (described in detail below): Application, Factory and PerRequest. The default is Application. You may create your own adaptors; if you do so you should use the full namespace as the value (MyApp::Adaptors::MySpecialAdaptor).

ADAPTORS

Out of the box this plugin comes with the following three adaptors. All canonical adaptors are under the namespace 'Catalyst::Model::InjectionHelpers'.

Application

Model is application scoped. This means you get one instance shared for the entire lifecycle of the application.

Factory

Model is scoped to the request. Each call to $c->model($model_name) returns a new instance of the model. You may pass additional parameters in the model call, which are merged to the global parameters defined in configuration and used as part of the object initialization.

PerRequest

Model is scoped to the request. The first time in a request that you call for the model, a new model is created. After that, all calls to the model return the original instance, until the request is completed, after which the instance is destroyed when the request goes out of scope.

The first time you call this model you may pass additional parameters, which get merged with the global configuration and used to initialize the model.

PerSession.

Scoped to a session. Requires the Session plugin. See Catalyst::Model::InjectionHelpers::PerSession for more.

Creating your own adaptor

Your new adaptor should consume the role Catalyst::ModelRole::InjectionHelpers and provide a method ACCEPT_CONTEXT which must return the component you wish to inject. Please review the existing adaptors and that role for insights.

transform_args

A coderef that you can use to transform configuration arguments into something more suitable for your class. For example, the configuration args is typically a hash, but your object class may require some positional arguments.

    MyApp->inject_components(
      'Model::Foo' => {
        from_class = 'Foo',
        transform_args => sub {
          my ($adaptor_instance, $coderef, $app, %args) = @_;
          my $path = delete $args{path},
          return ($path, %args);
        },
      },
    );

Should return the args as they as used by the initialization method of the 'from_class'.

Use 'transform_args' when you just need to tweak how your object uses arguments and use 'from_code' when you need more control on what kind of object is returned (in other words choose the smallest hammer for the job).

CONFIGURATION

This plugin defines the following possible configuration. As per Catalyst standards, these configuration keys fall under the 'Plugin::InjectionHelpers' namespace in the configuration hash.

adaptor_namespace

Default namespace to look for adaptors. Defaults to Catalyst::Model::InjectionHelpers

default_adaptor

The default adaptor to use, should you not set one. Defaults to 'Application'.

PRIOR ART

You may wish to review other similar approach on CPAN:

Catalyst::Model::Adaptor.

AUTHOR

John Napiorkowski email:jjnapiork@cpan.org

SEE ALSO

Catalyst, Catalyst::Model::InjectionHelpers::Application, Catalyst::Model::InjectionHelpers::Factory, Catalyst::Model::InjectionHelpers::PerRequest Catalyst::ModelRole::InjectionHelpers

COPYRIGHT & LICENSE

Copyright 2016, John Napiorkowski email:jjnapiork@cpan.org

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