Question

My experience is mostly limited to PHP, yet as far as I know both Rails and ASP.NET MVC have taken the same path.

The point is that nearly every web framework I’ve ever come across implements controller actions as methods, e.g. create, edit, show, etc. These methods reside in a single class like PostsController, but they hardly ever share state or dependencies, because only one of them gets called during the whole request.

That’s why to me this approach seems quite unreasonable, as the class only acts as some kind of namespace. Seeing examples with large chunks of barely related controller action code composing even larger controller classes doesn’t help either. Yet a lot of frameworks do exactly that, and only a few use a class for each action.

So the question is, why is it so? Perhaps it’s subjective, but I believe that I may have missed an important advantage of this approach.

Answer 1

I would argue that the MVC design pattern in general dictates this approach to building controllers. The main purpose of the controller is to provide the appropriate “wiring” between the associated view and the models it needs to interact with, along with any business logic needed to handle the input from the view. Controllers should just be a thin layer between these other components.
For example, Wikipedia describes the controller as follows:

The controller receives input and
initiates a response by making calls
on model objects. A controller accepts
input from the user and instructs the
model and viewport to perform actions
based on that input.

I do agree that controllers in other, non-web environments do maintain state, but the reason for the lack of state in PHP, for example, is simply that HTTP is a stateless protocol. Using MVC in this environment is inherently going to result in controllers that don’t maintain state.