Trouble casting UIView in iOS

Question

I have a class called FooView which is a subclass of UIView and I'm trying to cast a UIView object into FooView .

I do this as follows

FooView *myView = (FooView*) MyViewController.view
NSLog(@"Leg is a class of %@",NSStringFromClass([myView class])); // Get UIView here.

The ivar of MyViewController is a UIView type.

I get a UIView result, any idea why this happens?

Answer 1

Casting is a compile-time operation. It doesn't magically change the type of the object. It's mostly for compile time checking and a little runtime magic. myView is still a UIView , not a FooView .

These two lines in your question should give you your answer:

The ivar of MyViewController is a UIView type. I get a UIView result

All Objective-C objects have a pointer called isa that points to an object of type Class . Casting does not change that pointer, nor does it change the size of the object.

If you want to use a FooView , you need to change the property type in your controller and if you're using Interface Builder, change the type of the UIView in the inspector on the right.

Answer 2

You can create a loadView method in MyViewController that creates a FooView and sets it to self.view. It's for when you're not using a NIB.