InputAccessoryView's viewWillDisappear: method called early in iOS 9

Question

I've ran into quite an unfortunate bug in iOS 9. It seems that when you set a UITextField.inputAccessoryView, that view's viewWillDisappear: and viewDidDisappear: methods are called prematurely (right when the keyboard finishes animating up).

I've included a gif to demonstrate the issue. When the view turns red is when its viewWillDisappear: method has been called. Oddly when you dismiss the keyboard, viewWillDisappear: and viewDidDisappear: are called again. However, viewWillAppear: is only called once.

Has anyone run into a similar issue? I use viewWillDisappear: and viewDidDisappear: to wind down the controller, and obviously an early call is causing unwanted behaviour.

Note: Below is how I create and set the accessory view. Nothing notable in AccessoryViewController.m. Reproduced the issue in a clean project. And it is not present on iOS 8.

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField {
    if (self.textField.inputAccessoryView == nil) {
        self.textField.inputAccessoryView = self.vc.view;
    }
    return YES;
}

- (UIViewController *)vc {
    if (!_vc) _vc = [[AccessoryViewController alloc] init];
    return _vc;
}

Answer 1

The AccessoryViewController is not stored strongly on the ViewController. Store it in an instance variable so it does not get cleaned up.

My solution (Swift):

var accessoryView: AccessoryViewController! // works

vs

weak var accessoryView: AccessoryViewController!