Mixin 0.1.2

You want to add pod 'Mixin', '~> 0.1' similar to the following to your Podfile:

target 'MyApp' do
  pod 'Mixin', '~> 0.1'
end

Then run a pod install inside your terminal, or from CocoaPods.app.

Alternatively to give it a test run, run the command:

pod try Mixin

Mixin 0.1.2

By
Howard Yang

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

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, [email protected]

License

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