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Question

我正在尝试为 NotificationCenter

编写扩展

我发现语法有点多 "boilerplatey"，我想提供一个简单的扩展来简化发布和观察。

我可以像这样发送一个事件

NotificationCenter.dispatch(key: <#T##String#>, payload: <#T##[String : String]#>)

不过我想以类似的方式观察事件。

我正在尝试创建类似

的内容

NotificationCenter.observe(key: <#T##String#>, handler: <#T##() -> Void#>)

然而这是不正确的。我不确定如何处理传递应该在观察时触发的选择器函数？

这是我目前的尝试。

extension NotificationCenter {
    static func dispatch(key: String, payload: [String: String] = [:]) {
        NotificationCenter.default.post(name: NSNotification.Name(rawValue: key), object: nil, userInfo: payload)
    }
    static func observe(key: String, handler: ()->Void) {
        NotificationCenter.default.addObserver(
            self, selector: handler, name: NSNotification.Name(rawValue: key), object: nil
        )
    }
}

Answer 1

你可以这样使用：

extension NotificationCenter {

    class func observe(name: NSNotification.Name, handler: @escaping (Notification) -> Void) {
        self.default.addObserver(forName: name, object: nil, queue: .main, using: handler)
    }

}

那么你可以这样使用它：

NotificationCenter.observe(name: UIResponder.keyboardDidShowNotification) { notification in
    // do something
}

尽管如此，您绝对应该查看 https://developer.apple.com/documentation/foundation/notificationcenter/1411723-addobserver 关于注销观察的内容。

Answer 2

听起来你需要这样的东西

extension NotificationCenter {
    static func dispatch(key: String, payload: [String: String] = [:]) {
        self.default.post(name: NSNotification.Name(rawValue: key), object: nil, userInfo: payload)
    }
    static func observe(key: String, handler: @escaping (Notification) -> Void) {
        self.default.addObserver(forName: NSNotification.Name(rawValue: key), object: nil, queue: .main, using: handler)
    }
}

Answer 3

NotificationCenter - 一个有用但看起来笨重的界面，感觉代码有点臃肿，因为有人来自 UNIX-like 线程同步语义......所以，这些扩展基于 S.O . & the 'Net, with a couple twists.

extension Notification.Name {
    static let patientlyWaiting = Notification.Name("patientlyWaiting")
    // .
    // . list your arbitrary waiter names here...
    // .
}
extension NotificationCenter {
    static func wait(_ name : Notification.Name) async {
        for await _ in NotificationCenter.default.notifications(named: name) {
            break;
        }
    }
    static func post(_ name : Notification.Name) {
        NotificationCenter.default.post(name: name, object: nil)
    }
    static func postProcessing(_ name: Notification.Name, using block: @escaping (Notification) -> Void)  {
        NotificationCenter.default.addObserver(forName: name, object: nil, queue: OperationQueue.main, using: block)
    }
}

要使用它，像这样：

等待通知：

@IBAction func doSomethingAsychronouslyButtonPushed(_ sender: Any)  {
    doSomethingAsynchronously()
    NotificationCenter.postProcessing(.patientlyWaiting, using: { _ in
        print("doSomethingAsynchronouslyButton completion handler called")
    })
}

通知中：

func doSomethingAsynchronously() {
     for n in ["Time", " ",  "consuming", " - ", "whatever"] {
          print("\(n)", terminator: "")
     }
     print("\n")
     NotificationCenter.post(.patientlyWaiting) 
}

_{注意：您可以避免使用闭包并使用 Swift 语言的 recently-added async/[=14= 进行内联等待] 支持（参见'wait()function in the extensions shown above), but I didn't provide an example of using that because I haven't been able to invokeasyncfunctions from selectors, such as from aUIButtonpress, directly or indirectly; because, any function that usesawaitneeds to be declaredasync. Specifically, #selector(afunc(_:)) doesn't match functions declared async, and I'm unaware of a function signature syntax that accounts for an asyncin function declaration (to pass to #选择器（）`）。如果有人知道，请在评论中告诉我，我会更新答案。}

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Extending NotificationCenter

nsnotificationcenter

ios

swift