如何使两个插座都扩展（SWIFT 2）

Question

I created extension for UITextField. And I need the same extension for UITextView. How to make this extension available for all other views?

My extension code:

extension UITextField {

    func addTopBorderWithColor(color: UIColor, height: CGFloat) {
        let border = CALayer()
        border.backgroundColor = color.CGColor
        border.frame = CGRectMake(0, 0, self.frame.size.width, height)
        self.layer.addSublayer(border)
    }

    func addRightBorderWithColor(color: UIColor, height: CGFloat) {
        let border = CALayer()
        border.backgroundColor = color.CGColor
        border.frame = CGRectMake(self.frame.size.width - height, 0, height, self.frame.size.height)
        self.layer.addSublayer(border)
    }

    func addBottomBorderWithColor(color: UIColor, height: CGFloat) {
        let border = CALayer()
        border.backgroundColor = color.CGColor
        border.frame = CGRectMake(0, self.frame.size.height - height, self.frame.size.width, height)
        self.layer.addSublayer(border)
    }

    func addLeftBorderWithColor(color: UIColor, height: CGFloat) {
        let border = CALayer()
        border.backgroundColor = color.CGColor
        border.frame = CGRectMake(0, 0, height, self.frame.size.height)
        self.layer.addSublayer(border)
    }
}

Answer 1

You should only create the extension for UIView . As the other classes ( UITextField , UITextView , UILabel , ...) extend UIView , they all should have your functions available.

NOTE : This requires that the functions work for UIView and don't contain specific operations (eg accessing properties only available in UITextView ).

Answer 2

In the case when you want an extension for only a few classes, you could define a protocol and provide default implementations in the protocol, then extend the classes with the new protocol. Here's a trivial example you can run in playground:

protocol foo {
    func bar() -> String;
}

extension foo {
    func bar() -> String {
        return "bar"
    }
}

extension Float: foo {}
extension Int: foo {}


let i = 12
print(i.bar())

let f:Float = 1.0
print (f.bar())