A类是否可以保留B类的依赖关系，因为类A在调用方法后实例化了B类

Question

I have a class I call my Dispatcher and when its dispatch() method is run it instantiates the requested controller.

My AbstractController has a constructor like

public function __construct(RequestInterface $request, ResponseInterface $response, ViewFactory $viewFactory, ServiceFactory $serviceFactory)

As you can see my controllers have 4 dependencies.

At the moment when I instantiate my Dispatcher I inject the ViewFactory and ServiceFactory into its constructor and then when I run the dispatch() method I supply the Request and Response objects as arguments and I can then inject all four dependencies into my controller.

Would it be better to just supply all the controllers dependencies when calling the dispatch() method or supply them all in the constructor of the Dispatcher and then run a dispatch() method with no arguments or is there a better way overall?

Answer 1

You have 4 dependencies you want to inject in a new controller instance, 2 have a request/response life cycle and 2 have a longer life cycle (process?), before invoking some method on it. I would separate the creation of the controller from the invoking by creating a controller factory.

The controller factory would instantiate a controller using a method that receives only the request and reponse objects as parameters. The factory would be aware of the life cycle of the two longer lifed dependencies, perhaps share the same life cycle. The factory's user is then free to invoke any method they would like on the (abstract) controller returned. This is more flexible than the delegation pattern you propose. You could of course still use delegation, but then I would probably still have the Dispatcher only do dispatching and leave object creation to a factory.

Of course, there is no right answer with these kind of questions. It all depends on a lot of factors (requirements, size of codebase, the project, etc). Hope this helps though. Good luck!