Dependency Injection And Controllers In Laravel Framework

Laravel resource controllers provide the CRUD routes to the controller in a single line of code. A resource controller is used to create a controller that handles all the http requests stored by your application. The resource() is a static function like get() method that gives access to multiple routes that we can use in a controller.

Dependency Injection & Controllers

Constructor Injection

The Laravel service container is used to resolve all Laravel controllers. As a result, you are able to type-hint any dependencies your controller may need in its constructor. The declared dependencies will automatically be resolved and injected into the controller instance:

<?php

namespace App\Http\Controllers;

use App\Repositories\UserRepository;

class UserController extends Controller
{
    /**
     * The user repository instance.
     */
    protected $users;

    /**
     * Create a new controller instance.
     *
     * @param  UserRepository  $users
     * @return void
     */
    public function __construct(UserRepository $users)
    {
        $this->users = $users;
    }
}

You may also type-hint any Laravel contract. If the container can resolve it, you can type-hint it. Depending on your application, injecting your dependencies into your controller may provide better testability.

Method Injection

In addition to constructor injection, you may also type-hint dependencies on your controller's methods. A common use-case for method injection is injecting the Illuminate\Http\Request instance into your controller methods:
 

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class UserController extends Controller
{
    /**
     * Store a new user.
     *
     * @param  Request  $request
     * @return Response
     */
    public function store(Request $request)
    {
        $name = $request->name;

        //
    }
}

If your controller method is also expecting input from a route parameter, list your route arguments after your other dependencies. For example, if your route is defined like so:
 

Route::put('user/{id}', 'UserController@update');

You may still type-hint the Illuminate\Http\Request and access your id parameter by defining your controller method as follows:
 

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class UserController extends Controller
{
    /**
     * Update the given user.
     *
     * @param  Request  $request
     * @param  string  $id
     * @return Response
     */
    public function update(Request $request, $id)
    {
        //
    }
}