Why do UIViewControllers have xib files and UIViews do not?

When I create a new UIViewController in xcode, it offers to make me an associated nib for the interface. However, when I create a UIView, it does not. If my understanding of MVC is correct, views should really be the parts that contain the interface elements (i.e. the nib) while view controllers are the parts that hook the functionality to the views they control.

I'm sure I'll be able to get it working together either way, so开发者_运维问答 this is more of an exploratory question.

This seems like a case where I'm missing some fundamental understanding of how these two parts should be used. What am I missing?

Because UIView is usually not used in such way. However How do I associate a nib (.xib) file with a UIView?

The answer I eventually got that satisfied my interest was roughly this:

The job of a view controller is to manage a view hierarchy. Interface Builder is an excellent tool for creating view hierarchies. Xcode offers to create a .xib when you create a new view controller because chances are high that you'll want to load the controllers' views from a .xib.

.xib files aren't necessarily meant to hold every UIView (or subclass) that goes into the view, just a general outline of views that don't change during the life of the view. The other UIViews are much easier to create programmatically since they change often.

I had a similar confusion. Basically (according to the MVC) the View is contained inside the Controller. In the iPhone this means that UIViewController has a property called 'view' which is a UIView instance.

A XIB file (and this is not mentioned often) is a serialised UIView instance. It is roughly an XML sub format which represents a UIView with all its subsequent views. So when you create a UIViewController, a UIView is created in the form of a XIB and bounded to that controller.

A new UIView therefore does not have a XIB because they are essentially the same thing...