如何在Swift中使用Timer（以前称为NSTimer）？

这将起作用：

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公开给Objective-C，因此

@objc