Swift 3 参数：单变量，两种类型

Question

Anyone know if there's a way to have a parameter be of two types?

Such as for the function:

func email(from viewcontroller : (UIViewController, MFMailComposeViewControllerDelegate) {

}

Answer 1

Genericize your function's definition:

func email<T>(from viewController : T) where T: UIViewController, T: MFMailComposeViewControllerDelegate {
    // ...
}

Answer 2

In Swift 4

func email(from viewcontroller : UIViewController & MFMailComposeViewControllerDelegate) {
}

Elegant, short and intuitive.