Swift 中的 NSNotificationCenter addObserver [英] NSNotificationCenter addObserver in Swift

问题描述

如何在 Swift 中将观察者添加到默认通知中心?我正在尝试移植这行代码，当电池电量发生变化时发送通知.

How do you add an observer in Swift to the default notification center? I'm trying to port this line of code that sends a notification when the battery level changes.

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(batteryLevelChanged:) name:UIDeviceBatteryLevelDidChangeNotification object:nil];

推荐答案

与 Objective-C API 相同，但使用 Swift 的语法.

It's the same as the Objective-C API, but uses Swift's syntax.

Swift 4.2 &斯威夫特 5:

NotificationCenter.default.addObserver(
    self,
    selector: #selector(self.batteryLevelChanged),
    name: UIDevice.batteryLevelDidChangeNotification,
    object: nil)

如果你的观察者不是从 Objective-C 对象继承的，你必须在你的方法前面加上 @objc 以便将它用作选择器.

If your observer does not inherit from an Objective-C object, you must prefix your method with @objc in order to use it as a selector.

@objc private func batteryLevelChanged(notification: NSNotification){     
    //do stuff using the userInfo property of the notification object
}

参见 NSNotificationCenter 类参考，与 Objective-C API 交互

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