在类中观察静态var的值? [英] Observing a value of a static var in a class?

问题描述

我有一个static var的类，用于存储当前的在线连接状态.我想通过其他类观察ConnectionManager.online的值.我想用 KVO 来做到这一点，但是将static变量声明为dynamic会导致错误:

I have a class with a static var where the current online connection status is stored. I want to observe the value of ConnectionManager.online through other classes. I wanted to do this with KVO, but declaring a static variable as dynamic causes an error:

class ConnectionManager: NSObject {
    dynamic static var online = false
    // adding 'dynamic' declaration causes error:
    // "A declaration cannot be both 'final' and 'dynamic'
}

最优雅的方法是什么?

更新.这是我的KVO部分代码:

Update. This my code for the KVO part:

override func viewDidLoad() {
    super.viewDidLoad()

    ConnectionManager.addObserver(
        self,
        forKeyPath: "online",
        options: NSKeyValueObservingOptions(),
        context: nil
    )
}

override func observeValueForKeyPath(keyPath: String?, 
                                     ofObject object: AnyObject?, 
                                     change: [String : AnyObject]?, 
                                     context: UnsafeMutablePointer<Void>) {
    if keyPath == "online" {
        print("online status changed to: \(ConnectionManager.online)")
        // doesn't get printed on value changes
    }
}

推荐答案

到目前为止，Swift无法具有可观察的类属性. (实际上，静态属性只是其名称空间限制在类中的全局变量.)

As for now, Swift cannot have observable class properties. (In fact, static properties are just global variables with its namespace confined in a class.)

如果要使用KVO，请创建一个具有online属性的共享实例(单个类)，并将观察者添加到该实例中.

If you want to use KVO, create a shared instance (singleton class) which has online property and add observer to the instance.

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