在View Controller中从App Delegate访问变量

// 定义一个协议
protocol ViewControllerDelegate: AnyObject {
    var someVariable: String { get }
}

class ViewController: UIViewController, ViewControllerDelegate {
    var someVariable: String = "Hello, World!"

    // 其他代码...
}

class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    weak var viewControllerDelegate: ViewControllerDelegate?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // 设置ViewController为委托
        if let viewController = window?.rootViewController as? ViewControllerDelegate {
            viewControllerDelegate = viewController
        }
        return true
    }

    func someMethodInAppDelegate() {
        print(viewControllerDelegate?.someVariable ?? "Default Value")
    }
}

class ViewController: UIViewController {
    var someVariable: String = "Hello, World!"
    var variableClosure: ((String) -> Void)?

    // 其他代码...
}

class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        if let viewController = window?.rootViewController as? ViewController {
            viewController.variableClosure = { [weak self] variable in
                print(variable)
            }
        }
        return true
    }

    func someMethodInAppDelegate() {
        // 调用闭包来访问ViewController的变量
        viewControllerDelegate?.variableClosure?(viewControllerDelegate?.someVariable ?? "Default Value")
    }
}

// 在ViewController中发送通知
extension ViewController {
    func sendNotification() {
        NotificationCenter.default.post(name: .someNotification, object: nil, userInfo: ["someVariable": someVariable])
    }
}

// 在AppDelegate中监听通知
extension AppDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        NotificationCenter.default.addObserver(self, selector: #selector(handleNotification), name: .someNotification, object: nil)
        return true
    }

    @objc func handleNotification(notification: NSNotification) {
        if let variable = notification.userInfo?["someVariable"] as? String {
            print(variable)
        }
    }
}

// 定义通知名称
extension Notification.Name {
    static let someNotification = Notification.Name("someNotification")
}