A question about dependence and MVC on Cocoa

I'm a newbie in Cocoa developer, beside this I know well a lot of patterns. So far until now I understand that MVC have in mind avoid dependences between model, view and control. Well, I gave a look in some examples of controller and I found a behavior开发者_Go百科 that apparently do not agree with that goal. Normally, in theses examples, I found a controller creating a instance of model, in other words, the controller is explicitly dependent of the model. For me a solution could be the use of factory pattern to avoid dependence between controller and model.

What you think about it? How you solve that problem?

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In Cocoa, the controller's role is to mediate between the model and the view. There should be a wall between model and view, so you can swap out either one without the other noticing; the controller straddles this wall, and so knows about both.

So, yes, controllers generally do know about both the model and the view. In the Cocoa world, this is normal.

I have never found a good use for “dependency injection” (a.k.a. hiding controller code in model/view code files) or the factory pattern (objects that exist solely to make other objects). Classes should be self-contained; categories to extend them should be rare. And classes, at least in Cocoa, should be capable of making their own instances.