以编程方式设置UIButton的图像？

Question

我想在特定事件上设置UIButton的图像.这就是我做的:

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

Answer 1

Objective-C的

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

斯威夫特3

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