Observable

Simplified Swift pub/sub wrapper for NotificationCenter.

How is this useful?

This is a very simple library, the goals of which are;

to create a clean & concise implementation of an observer pattern around NotificationCenter
to bind events/notifications to objects so that they are only fired during the lifetime of the object
to make events statically typed to avoid any issues caused by using "magic" strings (e.g. typppos)

Aside from simply adding the Observable protocol to the object you would like to observe, the only other implementation requirement for the Observable object is to declare an ObservableEvent enum that contains all of the events that can be observed on that object.

Try it out!

Clone or download this repo and simply open the Observable.playground in Xcode to try it out.

Usage Example

Observable object

struct Television: Observable {
    
    /// Declaring a String enum named `ObservableEvent` is the only implementation requirement for the Observable object.
    enum ObservableEvent: String {
        case changedChannel, poweredOff, poweredOn
    }
    
    var channel = 0 {
        didSet {
            post(.changedChannel, with: channel)
        }
    }

}

Observer object

class TelevisionWatcher {
    
    private let tv = Television()
    
    init() {
        // Block example
        tv.subscribe(to: .poweredOn) { _ in
            print("TV was powered on.")
        }
        
        // Selector example
        tv.subscribe(to: .changedChannel, with: self, selector: #selector(handleChannelChange))
    }
    
    @objc private func handleChannelChange(notification: Notification) {
        guard let channelNumber = notification.object as? Int else { return }
        
        print("The TV is now on channel \(channelNumber)")
    }
    
}

dtrenz / Observable