A handy class to observe notifications with automatic unsubscribing and friendly syntax.

NotificationObserver.swift

// Free to use
// Written by Alexis Bridoux - https://github.com/ABridoux

/// Observes a notification and executes the provided block upon reception
///
/// Unregister the stored observer upon deinitialization
final class NotificationObserver {

    var name: Notification.Name
    var observer: NSObjectProtocol
    var center = NotificationCenter.default

    init(for name: Notification.Name, block: @escaping (Notification) -> Void) {
        self.name = name
        observer = center.addObserver(for: name, using: block)
    }

    deinit {
        center.removeObserver(observer, name: name)
    }
}

// MARK: - Array

extension Array where Element == NotificationObserver {

    mutating func append(name: NSNotification.Name, using block: @escaping (Notification) -> Void) {
        append(NotificationObserver(for: name, block: block))
    }
}

// MARK: - NotificationCenter extensions

extension NotificationCenter {

    func post(_ notificationName: NSNotification.Name) {
        post(name: notificationName, object: nil)
    }

    func addObserver(
        for notificationName: NSNotification.Name,
        using block: @escaping (Notification) -> Void)
    -> NSObjectProtocol {
        addObserver(forName: notificationName, object: nil, queue: nil, using: block)
    }

    func removeObserver(_ observer: NSObjectProtocol, name: NSNotification.Name) {
        removeObserver(observer, name: name, object: nil)
    }
}

Explanations

📖 Read the article
⬇️ Get the playground

Some examples

extension NSNotification.Name {
    static let orderIsReady = Self(rawValue: "orderIsReady")
}

struct Cook {
    var center = NotificationCenter.default

    func notifyOrderReady() {
        center.post(.orderIsReady)
    }
}

final class Client {
    var observer: NotificationObserver?

    func startObserving() {
        observer = NotificationObserver(for: .orderIsReady) { [weak self] _ in self?.orderIsReady() }
    }

    func orderIsReady() {
        print("😋")
    }
}

// MARK: Test

let cook = Cook()
var client: Client? = Client()
client?.startObserving()
cook.notifyOrderReady() // print 😋