How mvc pattern is implemented in iOS user interface? (view-based XCode temlpate)

I'm new to iphone development. There's a lot of books on this topic available. But most of the beginner's guides are mostly concerned with Interface Builder usage and lack the information about existing built in XCode code templates or something that could help me in understanding MVC implementation in code. I found that it is possible to write working iOS program without ViewController at all. Well, it seems to me like that after working with the sample code called ViewTransitions.

So, the question is - why is that possible to avoid ViewController implementation in a program that has an interface with a button? If the answer is going to be too long, could you please recommend k开发者_运维技巧ind of tutorial or manual covering this topic.

Thanks in advance.

@user697562's answer is essentially correct: in the case of ViewTransitions, the role of the controller is played by the app delegate. The app does next to nothing -- it just switches betweeen two views to demonstrate several possible transition effects -- so a UIViewController isn't really needed there.

Notice that there's also nothing in ViewTransitions that you could really call a model object. If you're looking for a strong example of MVC, ViewTransitions isn't the best project to look at. Other sample projects, such as TheElements, give a better demonstration of MVC in action.

There is a concept called delegation. A concept which helps maintain MVC. It helps to keep the model separate from controllers. For eg: - UITableView/UICollectionView , which knows how to display the data and other ui stuff. But it does not know which cell to display or what data to display at a particular index. And this is where delegation and the delegate object comes into place. UICollectionView handles all the view part whereas all the non view part is handled by the delgate object, which gives the required data for the view. This way a delegate(usually a separate view controller) acts as a data source and UICollectionView as a ui renderer.

in ViewTransitions, there IS an App Delegate, which is kind of your sole "controller". Even ViewTransitions has:

transition.delegate = self;    

IOS is a bit different from some frameworks in that you aren't as "in control" of what is going on. It often uses a delegation model where you set your code as the delegate, but it (IOS) is in control. Still, you can write in MVC style, it's just your "C" isn't fully in charge.