Do I have to release this variable?

UIViewController *parentController;
for (UIView* next = [self superview]; next; next = next.superview) {
    UIResponder* nextResponder = [next nextResponder];
    if ([nextResponder isKindOfClass:[UIViewController class]]) {
        pare开发者_JAVA技巧ntController = (UIViewController*)nextResponder;
    }
}

In this code, do I have to release the parentController? Then, when?

As you didn't take the ownership(retain/alloc/copy/new) of parentController object so you don't have to release it.

You don't have release it because you haven't increase it's retain count (by new, alloc, retain or copy).

No. You are not taking ownership, so no need to release it either.