Cocoa MVC implementation

I'm not very experienced with Cocoa but I am with MVC and coding in general. I come from an ActionScript background, so I'm very familiar with PureMVC.

I understand the fundamentals of Cocoas version of MVC. All works fine with very tiny appli开发者_Python百科cations. But how do I have to setup my architecture for larger applications? How should I manage my model objects and the communications between all the parts? How do I pass my instances between them. Is it a good idea to use Singletons which map my instances?

For now I used the Objective C PureMVC implementation. For those who know PureMVC: Instead of using Mediator subclasses, I've created ViewController subclasses which implement the IMediator Protocol, because in my opinion Mediators and ViewControllers are almost the same and I do not lose all the ViewController stuff.

But I definitely want to go an Apple approved and well-established way for future projects. Can anyone give my some good architecture approaches?

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Refer some projects from Apple developer site.
Model-View-Controller