swift-keypath

问题 (I say "more" in my title because this question is an appendix to my How does Swift ReferenceWritableKeyPath work with an Optional property?.) In my code, self.iv is an outlet property: @IBOutlet weak var iv: UIImageView! Now, will this compile? let im = UIImage() let kp = \UIImageView.image self.iv[keyPath:kp] = im // error No! We are told that something here must be unwrapped, although it is not entirely obvious what it is: Value of optional type 'UIImage?' must be unwrapped to a value of

问题 Ground of Being : It will help, before reading, to know that you cannot assign a UIImage to an image view outlet's image property through the keypath \UIImageView.image . Here's the property: @IBOutlet weak var iv: UIImageView! Now, will this compile? let im = UIImage() let kp = \UIImageView.image self.iv[keyPath:kp] = im // error No! Value of optional type 'UIImage?' must be unwrapped to a value of type 'UIImage' Okay, now we're ready for the actual use case. What I'm actually trying to