以編程方式設置UIButton的圖像？

Question

我想在特定事件上設置UIButton的圖像。這是我做過什麼：

btn.setImage(UIImage(named: "star")) 

Answer 1

Objective-C的

UIImage *img = [UIImage imageNamed:@"star.png"]; 
[btn setImage:image forState:UIControlStateNormal]; 

斯威夫特3

let img = UIImage(named: "star") 
btn.setImage(img , forState: .normal)