Application Services

Application Services are the middleware between the outside world and the Domain logic. The purpose of such a mechanism is to transform commands from the outside world into meaningful Domain instructions.

Let's consider the User signs up to our platform use case. Starting with an outside-in approach: from the delivery mechanism, we need to compose the input request for our Domain operation. Using a framework like Symfony as the delivery mechanism, the code would look something like this:

class SignUpController extends Controller
{
    public function signUpAction(Request $request)
    {
        $signUpService = new SignUpUserService(
            $this->get('user_repository')
        );

        try {
            $response = $signUpService->execute(new SignUpUserRequest(
                $request->request->get('email'),
                $request->request->get('password')
            ));
        } catch (UserAlreadyExistsException $e) {
            return...