How to implement the "didset of swift" in objective-c?

Question

Swift (from the book 《iOS Animations by Tutorials:Chapter 12》 released by http://www.raywenderlich.com/):

let photoLayer = CALayer()  @IBInspectable   var image: UIImage! {     didSet {       photoLayer.contents = image.CGImage     } } 

How can I implement the above syntax in objective-c? I know only to set the property of photoLayer and image like below:

@property (strong, nonatomic) CALayer *photoLayer; @property (strong, nonatomic) IBInspectable UIImage *image; 

But i do not know how to implement didset{...} parts using objective-c syntax, please help!

Answer 1

override the setter and implement the setter yourself.

- (void)setImage:(UIImage *)image {     if (_image != image) {         _image = image;         photoLayer.contents = image.CGImage;     } }