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?

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

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

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