Awesome

Mixin 🍹

Why?

Swift is Protocol-Oriented Programming, and it's more powerful by default implementations of extensions of protocols. You can mixin methods to classes like Ruby's Mixin.

However, iOS as a UI framework, objects like UIViewController have their own life cyle, if you can't listen life cyle methods, extensions as mixin don't really help.

For example, I write a protocol with extension to listen keyboard events

protocol KeyboardMixin {
    var keyboardHeight: CGFloat? { set get }
    func registerKeyboard()
    func deregisterKeyboard()
}

extension KeyboardMixin {
    func registerKeyboard() {
        NotificationCenter.default.addObserver(forName: NSNotification.Name.UIKeyboardWillHide, object: nil, queue: nil) { [weak self] notification in
            self?.keyboardHeight = nil
        }
        NotificationCenter.default.addObserver(forName: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil, queue: nil) { [weak self] notification in
            if let keyboardSize = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
                self?.keyboardHeight = keyboardSize.height
            }
        }
    }
    func deregisterKeyboard() {
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillHide, object: nil)
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil)
    }
}

But I still need to register and deregister by myself

class ViewController: UIViewController, KeyboardMixin {
    var keyboardHeight: CGFloat? {
        didSet { }
    }
    override func viewWillAppear(_ animated: Bool) {
        registerKeyboard()
    }
    override func viewWillDisappear(_ animated: Bool) {
        deregisterKeyboard()
    }
}

The problem is why can't I mixin something to existing methods e.g. UIViewController life cyle?

If you have programmed React.js, you'll find its Mixin mechanism is very useful. So I just copy the idea to iOS. After using this package, you can write a mixin like this.

public protocol KeyboardMixin: ViewControllerMixinable {
    var keyboardHeight: CGFloat? { set get }
}

public extension KeyboardMixin {
    private func registerKeyboard() {
        NotificationCenter.default.addObserver(forName: NSNotification.Name.UIKeyboardWillHide, object: nil, queue: nil) { [weak self] notification in
            self?.keyboardHeight = nil
        }
        NotificationCenter.default.addObserver(forName: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil, queue: nil) { [weak self] notification in
            if let keyboardSize = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
                self?.keyboardHeight = keyboardSize.height
            }
        }
    }
    private func deregisterKeyboard() {
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillHide, object: nil)
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil)
    }
    fileprivate func viewWillAppear(_ animated: Bool) {
        registerKeyboard()
    }
    fileprivate func viewWillDisappear(_ animated: Bool) {
        deregisterKeyboard()
    }
}

And use it like below

class ViewController: UIViewController, KeyboardMixin {
    var keyboardHeight: CGFloat? {
        didSet { }
    }
    override func viewWillAppear(_ animated: Bool) {
        // Don't worry, you can still do things here...
    }
}

It can't be simpler!

How it works

This package uses iOS runtime to swizzle methods, so all override methods and mixins' methods will be called simultaneously.

Support

This package support mixin to

• UIViewControllerLifeCycle
• ExtendTableViewDelegate
• UIScrollViewDelegate
• UITextFieldDelegate

Example

Check out Example ViewController, it shows how amazing to use Mixin

• How to use mixins
• How to make mixins

Requirements

Only tested in Swift 4

Installation

Mixin is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'Mixin'

Author

Howard Yang, appdevoney@gmail.com

License

Mixin is available under the MIT license. See the LICENSE file for more info.