Swift 操场上有替代品吗？

我正在试验ipad的Swift Playgrounds，我正在尝试制作一个基本的计时器这是我使用的代码

import UIKit
import ObjectiveC
import CoreFoundation
import XCPlayground

XCPSetExecutionShouldContinueIndefinitely()

class StopWatch {
    var myCounter = 0

    func timer() {
        var timer = Timer.scheduledTimer(
            timeInterval: 1, 
            target: self, 
            selector: Selector("incrementCounter:"),
            userInfo: nil,
            repeats: true
        )
    }

    @objc func incrementCounter(mytimer:Timer) { 
        myCounter = myCounter + 1 
        print(myCounter)
    }
}

var myStopWatch = StopWatch()
myStopWatch.timer()

然而，每次我运行它时，它都会反复出现错误。我认为这是因为ipad的swift playgrounds中没有import xcPlaygrounds以及它附带的所有功能和命令。我想知道是否有此模块的替代品或更好的方法

---

谢谢

如果您正在与swift3一起使用游乐场，您可以使用下面的代码

“XCPSetExecutionShouldContinueIndefinitely”已被弃用，因此我添加了

PlaygroundSupport模块，并将NeedsDefiniteExecution值设置为true

import PlaygroundSupport

PlaygroundPage.current.needsIndefiniteExecution = true

class StopWatch {
    var myCounter = 0


    func timer() {
        let _ = Timer.scheduledTimer( timeInterval: 1, target: self, selector: #selector(incrementCounter(mytimer:)), userInfo: nil, repeats: true)
    }

    @objc func incrementCounter(mytimer:Timer) {
        myCounter = myCounter + 1
        print(myCounter)
    }
}

var myStopWatch = StopWatch()
myStopWatch.timer()

---

如果您正在使用操场与swift3，您可以使用下面的代码

“XCPSetExecutionShouldContinueIndefinitely”已被弃用，因此我添加了

PlaygroundSupport模块，并将NeedsDefiniteExecution值设置为true

import PlaygroundSupport

PlaygroundPage.current.needsIndefiniteExecution = true

class StopWatch {
    var myCounter = 0


    func timer() {
        let _ = Timer.scheduledTimer( timeInterval: 1, target: self, selector: #selector(incrementCounter(mytimer:)), userInfo: nil, repeats: true)
    }

    @objc func incrementCounter(mytimer:Timer) {
        myCounter = myCounter + 1
        print(myCounter)
    }
}

var myStopWatch = StopWatch()
myStopWatch.timer()