10. View
• UIView coordinate
• View’s location and size expressed in two ways
• Frame is in superview’s coordinate system
• Bounds is in local coordinate system
Model objects encapsulate the data specific to an application and define the logic and computation that manipulate and process that data. For example, a model object might represent a character in a game or a contact in an address book.
Model = What your application is
Controller = How your model is presented to the user
A view object is an object in an application that users can see. A view object knows how to draw itself and can respond to user actions.
A controller object acts as an intermediary between one or more of an application’s view objects and one or more of its model objects. Controller objects are thus a conduit through which view objects learn about changes in model objects and vice versa.
UIView objects are where the real magic begins to happen. They are attached to the UIWindow object and draw their contents when directed to do so by the window. The visual interface of your app is essentially a set of UIView objects, which are themselves managed by UIViewController objects.
http://b2b.cbsimg.net/blogs/aprime_katner_view_controllers.png
outermost layer: UIWindow
The UIScreen object represents the physical iPhone or iPad screen. Other than to perhaps query the size (the so-called bounds) of the screen, you will typically not interact much with the UIScreen object.
The UIWindow object provides drawing support for the screen, and your app will usually have just one. Other than setting the UIWindow object's initial root view controller (discussed below), you won't interact with the UIWindow object very much either.
UIViewController objects interact with UIViews to determine what's displayed by the views, handle any interactions with the user, and perform the logic of your program.