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!
This package uses iOS runtime to swizzle methods, so all override methods and mixins' methods will be called simultaneously.
This package support mixin to
- UIViewControllerLifeCycle
- ExtendTableViewDelegate
- UIScrollViewDelegate
- UITextFieldDelegate
Check out Example ViewController, it shows how amazing to use Mixin
Only tested in Swift 4
Mixin is available through CocoaPods. To install it, simply add the following line to your Podfile:
pod 'Mixin'Howard Yang, appdevoney@gmail.com
Mixin is available under the MIT license. See the LICENSE file for more info.
