函数有参数时 Swift Timer 错误

Question

我正在尝试制作一个每隔一秒激活一次的函数，它将一个变量加 1 (texttimer) 并将一个字母添加到一个字符串 (typedStory) ，显示在标签上 (storyLabel)。

一切正常，直到我向函数添加一个参数 (finalStory)。现在我收到一个错误:

-[__NSCFTimer substringToIndex:]: unrecognized selector sent to instance

这是我的代码:

func textTypeWelcome(finalStory: NSString){
    var newTimer2 = Timer.scheduledTimer(timeInterval: 0.05, target: self, selector: #selector(GameScene.textTypeWelcome), userInfo: finalStory, repeats: false)
    texttimer += 1
    typedStory = finalStory.substring(to: texttimer)
    storyLabel.text = typedStory

}

代码有效，但是如果我删除参数并将 userInfo 设置为 nil，则不会执行我想要的操作。

有人知道解决办法吗？谢谢!

Answer 1

不，那行不通，action 方法将 timer 作为参数——错误消息告诉你的——你从 userInfo< 得到 finalStory/ 参数。

func textTypeWelcome(timer: Timer) {
    let finalStory = timer.userInfo as! String
    var newTimer2 = Timer.scheduledTimer(timeInterval: 0.05, target: self, selector: #selector(GameScene.textTypeWelcome), userInfo: finalStory, repeats: false)
    texttimer += 1
    typedStory = finalStory.substring(to: texttimer)
    storyLabel.text = typedStory
}

在 Playground 中试试这个

class Foo  : NSObject {

    let string = "Hello World"
    var counter = 1

    var typedStory = ""

    var timer = Timer()

    override init() {
        super.init()
        timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(timerFired), userInfo: nil, repeats: true)
        print("timer started")
    }

    func timerFired(timer : Timer) {

        typedStory = string.substring(to: string.index(string.startIndex, offsetBy: counter))
        print(typedStory)
        if typedStory == string {
            timer.invalidate()
            print("timer stopped")
        } else {
            counter += 1
        }
    }
}

let foo = Foo()

你必须添加这些行

import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

允许异步API