In Objective-C where is textfielddoneediting originally declared?

I've performed a pretty exhaustive search of the documentation namely: UIViewController, UITextField, and UITextFieldDelegate, but I can't figure out where the method "textFieldDoneEditing" is originally declared.

I know that I have to use it in my ViewController to get the keypad to disappear in this manner:

开发者_如何学C- (IBAction)textFieldDoneEditing:(id)sender
{
    [sender resignFirstResponder];
}

But is method part of a protocol that is inherently implemented by UIViewController?

Thanks

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Without seeing the other code, I suspect this was connected to the textfield via interface builder connecting to the Editing Did End event. There is no textFieldDoneEditing method in any of UITextField parent classes.