Playing with Laravel Lumen: simple RESTful trait.

RestControllerTrait.php

<?php namespace App\Http\Controllers;

use Illuminate\Http\Request;

trait RestControllerTrait
{
	public function index()
    {
        $m = self::MODEL;
        return $this->listResponse($m::all());
    }

    public function show($id)
    {
        $m = self::MODEL;
    	if($data = $m::find($id))
        {
            return $this->showResponse($data);
        }
        return $this->notFoundResponse();
    }

    public function store(Request $request)
    {
        $m = self::MODEL;
        try
        {
            $v = \Validator::make($request->all(), $this->validationRules);

            if($v->fails())
            {
                throw new \Exception("ValidationException");
            }
            $data = $m::create(\Request::all());
            return $this->createdResponse($data);
        }catch(\Exception $ex)
        {
            $data = ['form_validations' => $v->errors(), 'exception' => $ex->getMessage()];
            return $this->clientErrorResponse($data);
        }
        
    }

    public function update($id)
    {
    	$m = self::MODEL;

        if(!$data = $m::find($id))
        {
            return $this->notFoundResponse();   
        }

        try
        {
            $v = \Validator::make(\Request::all(), $this->validationRules);

            if($v->fails())
            {
                throw new \Exception("ValidationException");
            }
            $data->fill(\Request::all());
            $data->save();
            return $this->showResponse($data);
        }catch(\Exception $ex)
        {
            $data = ['form_validations' => $v->errors(), 'exception' => $ex->getMessage()];
            return $this->clientErrorResponse($data);
        }
    }

    public function destroy($id)
    {
        $m = self::MODEL;
    	if(!$data = $m::find($id))
        {
            return $this->notFoundResponse();   
        }
        $data->delete();
        return $this->deletedResponse();
    }

    protected function createdResponse($data)
    {
        $response = [
        'code' => 201,
        'status' => 'succcess',
        'data' => $data
        ];
        return response()->json($response, $response['code']);
    }

    protected function showResponse($data)
    {
        $response = [
        'code' => 200,
        'status' => 'succcess',
        'data' => $data
        ];
        return response()->json($response, $response['code']);
    }

    protected function listResponse($data)
    {
        $response = [
        'code' => 200,
        'status' => 'succcess',
        'data' => $data
        ];
        return response()->json($response, $response['code']);
    }

    protected function notFoundResponse()
    {
        $response = [
        'code' => 404,
        'status' => 'error',
        'data' => 'Resource Not Found',
        'message' => 'Not Found'
        ];
        return response()->json($response, $response['code']);
    }

    protected function deletedResponse()
    {
        $response = [
        'code' => 204,
        'status' => 'success',
        'data' => [],
        'message' => 'Resource deleted'
        ];
        return response()->json($response, $response['code']);
    }

    protected function clientErrorResponse($data)
    {
        $response = [
        'code' => 422,
        'status' => 'error',
        'data' => $data,
        'message' => 'Unprocessable entity'
        ];
        return response()->json($response, $response['code']);
    }

}

routes.php

<?php

/*
|--------------------------------------------------------------------------
| Application Routes
|--------------------------------------------------------------------------
|
| Here is where you can register all of the routes for an application.
| It's a breeze. Simply tell Laravel the URIs it should respond to
| and give it the controller to call when that URI is requested.
|
*/

function rest($path, $controller)
{
	global $app;
	
	$app->get($path, $controller.'@index');
	$app->get($path.'/{id}', $controller.'@show');
	$app->post($path, $controller.'@store');
	$app->put($path.'/{id}', $controller.'@update');
	$app->delete($path.'/{id}', $controller.'@destroy');
}

rest('/user', 'App\Http\Controllers\UserController');

$app->get('/', function() use ($app) {
    return $app->welcome();
});

UserController.php

<?php namespace App\Http\Controllers;

use Laravel\Lumen\Routing\Controller as BaseController;

class UserController extends BaseController
{
    use RestControllerTrait;

    const MODEL = 'App\Models\User';

    protected $validationRules = ['username' => 'required', 'name' => 'required', 'password' => 'required'];
}

@meness look at this solution.

You can use "exists" validation rule instead of :
if (!$data = $model::find($id)) { return $this->notFoundResponse(); }