BorderView protocol

BorderView.swift

// blueprint
/// This protocol is constrained to types that conform to UIView - which is most UI elements
protocol BorderView: UIView {
    func addBorder(borderWidth: CGFloat, borderColor: CGColor)
}

// default implementation (optional)
extension BorderView {
    func addBorder(borderWidth: CGFloat = 1, borderColor: CGColor = UIColor.lightGray.cgColor) {
        self.layer.borderWidth = borderWidth
        self.layer.borderColor = borderColor
    }
}
// adopt
class MyBorderedView: UIView, BorderView {
    func commonInit() {
        addBorder()
    }
    // override is required for existing methods we want to use
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    // this is a required initializer for all UIViews - used by the storyboard. in programmatic applications, it's often common to see this produce a FatalError as a signal to other developers not to use that initializer
    // since we're using storyboards... it's pretty important lol
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
}

class MyBorderedTextField: UITextField, BorderView {
    func commonInit() {
        addBorder()
    }
    // override is required for existing methods we want to use
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    // this is a required initializer for all UIViews - used by the storyboard. in programmatic applications, it's often common to see this produce a FatalError as a signal to other developers not to use that initializer
    // since we're using storyboards... it's pretty important lol
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
}


// instantiate
let view: BorderView = MyBorderedTextField()
print(view.layer.borderWidth)