如何在 Swift 中使用 Timer(以前称为 NSTimer)?

问题描述

我试过了

var timer = NSTimer()
timer(timeInterval: 0.01, target: self, selector: update, userInfo: nil, repeats: false)

但是，我有一个错误说

'(timeInterval: $T1, target: ViewController, selector: () -> (), userInfo: NilType, repeats: Bool) -> $T6' is not identical to 'NSTimer'

推荐答案

这会起作用:

override func viewDidLoad() {
    super.viewDidLoad()
    // Swift block syntax (iOS 10+)
    let timer = Timer(timeInterval: 0.4, repeats: true) { _ in print("Done!") }
    // Swift >=3 selector syntax
    let timer = Timer.scheduledTimer(timeInterval: 0.4, target: self, selector: #selector(self.update), userInfo: nil, repeats: true)
    // Swift 2.2 selector syntax
    let timer = NSTimer.scheduledTimerWithTimeInterval(0.4, target: self, selector: #selector(MyClass.update), userInfo: nil, repeats: true)
    // Swift <2.2 selector syntax
    let timer = NSTimer.scheduledTimerWithTimeInterval(0.4, target: self, selector: "update", userInfo: nil, repeats: true)
}

// must be internal or public.
@objc func update() {
    // Something cool
}

对于 Swift 4，要获取选择器的方法必须暴露给 Objective-C，因此必须在方法声明中添加 @objc 属性.

For Swift 4, the method of which you want to get the selector must be exposed to Objective-C, thus @objc attribute must be added to the method declaration.

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