Dependency Injection Container Plugin for CakePHP 3

This plugin adds the ability to configure object instances and their dependencies before they are used, and to store them into a container class to easy access.

It uses the clean and flexible Ray.Di Library which is a PHP dependency injection framework in the style of "Google Guice".

Ray.Di also allows you to program using AOP, that is, decorating the configured instances so some logic can be run before or after any of their methods.

Installation

You can install this plugin into your CakePHP application using composer.

composer require lorenzo/piping-bag=dev-master

Configuration

You will need to add the following line to your application's bootstrap.php file:

Plugin::load('PipingBag', ['bootstrap' => true]);

For getting injection in your controllers to work you need to to replace the following line in your config/bootstrap.php:

DispatcherFactory::add('ControllerFactory');

With the following:

DispatcherFactory::add('PipingBag\Routing\Filter\ControllerFactoryFilter');

Additionally, you can configure the modules to be used and caching options in your config/app.php file.

'PipingBag' => [
    'modules' => ['MyWebModule', 'AnotherModule', 'APlugin.SuperModule'],
    'cacheConfig' => 'default'
]

Modules can also be returned as instances in the configuration array:

'PipingBag' => [
    'modules' => [new App\Di\Module\MyWebModule()],
    'cacheConfig' => 'default'
]

Finally, if you wish to tune your modules before they are registered, you can use a callable function:

'PipingBag' => [
    'modules' => function () {
        return [new MyWebModule()];
    },
    'cacheConfig' => 'default'
]

What is a Module anyway?

Modules are classes that describe how instances and their dependencies should be constructed, they provide a natural way of grouping configurations. An example module looks like this:

// in app/src/Di/Module/MyModule.php

namespace App\Di\Module;

use Ray\Di\AbstractModule;
class MyModule extends AbstractModule
{
    public function configure()
    {
        $this->bind('MovieApp\FinderInterface')->to('MovieApp\Finder');
        $this->bind('MovieApp\HttpClientInterface')->to('Guzzle\HttpClient');
        $this->install(new OtherModule()); // Modules can install other modules
    }
}

Modules are, by convention, placed in your src/Di/Module folder. Read more about creating modules and how to bind instances to names in the Official Ray.Di Docs.

Usage

After creating and passing the modules in the configuration, you can get instance of any class and have their dependencies resolved following the rules created in the modules:

use PipingBag\Di\PipingBag;

$httpClient = PipingBag::get('MovieApp\HttpClientInterface');

Injecting Dependencies in Controllers

Ray.Di is able to inject instances to your controllers based on annotations:

// in src/Controller/ArticlesController.php

use App\Controller\AppController;
use MovieApp\HttpClientInterface;
use Ray\Di\Di\Inject; // This is important

class ArticlesController extends AppController
{

    /**
     * @Inject
     */
    public function setHttpClient(HttpClientInterface $connection)
    {
        $this->httpClient = $connection;
    }
}

As soon as the controller is created, all methods having the @Inject annotation will get instances of the hinted class passed. This works for constructors as well.

Injecting Dependencies in Controller Actions

It is also possible to inject dependencies directly in the controller actions. When doing this, add the type-hinted dependency to the end of the arguments and set the default value to null, it is also required to annotate the method using @Assisted

// in src/Controller/ArticlesController.php

use App\Controller\AppController;
use MovieApp\HttpClientInterface;
use PipingBag\Annotation\Assisted; // This is important

class ArticlesController extends AppController
{

    /**
     * @Assisted
     */
    public function edit($id, HttpClientInterface $connection = null)
    {
        $article = $this->Articles->get($id)
        $connection->post(...);
    }
}

Injecting Dependencies in Shells

Shells are also able to receive dependencies via the @Inject annotation. But first, you need to change the cake console executable to use PipingBag. Open your bin/cake.php file and make it look like this:

    // bin/cake.php
    ...
    exit(PipingBag\Console\ShellDispatcher::run($argv)); // Changed namespace of ShellDispatcher

Then you can apply annotations to your shells:

use Cake\Console\Shell;
use Ray\Di\Di\Inject; // This is important

class MyShell extends Shell
{
    /**
     * @Inject
     */
    public function setHttpClient(HttpClientInterface $connection)
    {
        $this->httpClient = $connection;
    }

}