Question

I am learning Symfony2, and part of the documentation on controllers states that the methods on the controller object are actually the controllers, whereas the object is more of a controller container.

Which part specifically is referred to as the controller(s)? I’m new to MVC and OOP, so I’m just trying to make sure I have it right.

Answer 1

the page describes actually a convention endorsed by Symfony2 creators.

in some MVC frameworks (esp. in Java) controllers are implemented by one-class-per-controller convention, e.g.:

class ListContactsController {
    public function start() {
      // query db...
      return ...;
    }
}

class AddContactController {
    public function start($name, $details) {
      // insert into db...
      return ...;
    }
}

note that every controller-class has one method start() that defines what the controller actually does

in other MVC frameworks (like Symfony2 or cake-php) controllers are implemented by one-method-per-controller convention, grouped together for convenience, e.g.:

class ContactsController {
    public function list() {
      // query db...
      return ...;
    }

    public function add($name, $details) {
      // insert into db...
      return ...;
    }
}

here the convention assumes every controller is implemented as a method rather than a separate class with a particular method like start()

EDIT: another way of thinking about this difference is this:

• one-class-per-controller assumes there is one controller instance (might hold internal state) and when user interacts with the view, view is communicating with that controller instance via callbacks i.e. methods in controller’s class.
• one-method-per-controller assumes any state is contained within parameters that are passed to methods, and when user interacts with the view, view is communicating with separate controllers/actions. those controllers are seen as independent concepts.