Observer Pattern in Swift

observer-pattern.swift

/*
Observer Pattern
1. The subscriber is the "observer" object and receives updates. `AppCoordinator`
2. The publisher is the "observable" object and sends updates. `LoginViewController`
3. The value is the underlying object that's changed.
*/
import UIKit

final class AppCoordinator {
    init() {
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(loginSuccess),
                                               name: Notification.Name("LoginSuccessNotification"),
                                               object: nil)
    }
    
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    @objc private func loginSuccess() {
        // Change root view here
        print("Change root view to Home screen for example")
    }
}

final class LoginViewController {
    func login() {
        // Call login API
        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
            // Login Success
            NotificationCenter.default.post(name: Notification.Name("LoginSuccessNotification"),
                                            object: nil)
        }
    }
}

let appCoordinator = AppCoordinator()
let loginView = LoginViewController()
loginView.login()

/*
Change root view to Home screen for example
*/