Question

I have a UIView called Product, which contains a sub UIView called Postcode.

In the Postcode UIView i have a simple form (one UITextField and one UIButton).

When the UIButton is clicked a method (called -storeData) is run inside postcode view … which works as intended.

Now inside storeData I would like to call a method in the superview Product.

This is what i tried doing, but im getting a warning:

if ([[self superview] class] == [ProductView class]) {
        ProductView *p = [self superview]; 
        [p handlePostChange]; 
    }

// Get this warning from this line ProductView *p = [self superview];

PostView.m:124:28: Incompatible pointer types initializing
‘ProductView *__strong’ with an expression of type ‘UIView *’

Answer 1

The call to [self superview] returns a UIView pointer. You are trying to do the equivalent of:

UIView *view;
ProductView *p = view;

The compiler has no way to know that at runtime, view will really be of type ProductView. This is why the compiler complains.

The solution, as was stated, is to use a cast:

UIView *view;
ProductView *p = (ProductView *)view;

The cast tells the compiler “hey, don’t worry, I know what I’m doing. It really is a ProductView“. Of course if you are wrong, the app will most likely crash at runtime.

The following is perfectly fine:

ProductView *p;
UIView *view = p;

This is safe, gives no warning, and requires no cast. This works because it is known that ProductView is a subclass of UIView.