在Swift中准确测量时间以进行设备比较 [英] Measuring Time Accurately in Swift for Comparison Across Devices

问题描述

我需要能够记录反应时间，从屏幕加载或问题标签刷新到用户点击数字按钮。我没有在Apple上找到关于此的文档非常有帮助。 NSDate 不够准确，我需要至少测量到毫秒。 mach_absolute_time 似乎受到游戏设计师的青睐，因为它内部一致，但它不适用于这个应用程序，因为我需要跨设备比较数据， mach_absolute_time 是CPU相关时间。 此Apple Dev Q& A 建议使用 NanosecondsToAbsolute 和 DurationToAbsolute 但它在obj-c中，我找不到快捷的等效文档。

I need to be able to record reaction time, from when the screen loads or the question label refreshes until the user taps a number button. I'm not finding documentation from Apple on this to be very helpful. NSDate is not accurate enough, I need to measure to milliseconds at least. mach_absolute_time seems to be favored by game designers because it is internally consistent, but it won't work for this application because I need to compare data across devices, and mach_absolute_time is CPU dependent time. This Apple Dev Q&A suggests using NanosecondsToAbsolute and DurationToAbsolute but it's in obj-c and I can't find a swift equivalent documentation.

我有没有找到 NanosecondsToAbsolute 和 DurationToAbsolute 的快速版本？还有其他一些方法可以做到这一点吗？

Is there a swift version of NanosecondsToAbsolute and DurationToAbsolute that I'm just not finding? Some other way to do this consistently?

这是我试图将时间添加到的代码：

Here's the code I'm trying to add the times to:

class EmotionQuestionsViewController: UIViewController{

    override func viewDidLoad() {
        super.viewDidLoad()

//mark "startTime" when view loads
    }

    @IBOutlet var questionLabel: UILabel!
    var timeResultsStack = [String]()

    var questionsStack = ["HAPPY", "ANXIOUS"]
    var questionResultsStack = [String]()
    var questionStackArrayIndex = 1

    @IBAction func RecordValueFromNumericalScaleOneToSeven(sender: UIButton) {

//mark durration time as currentTime - startTime, append to timeResultsStack

        let value = sender.currentTitle!
        questionResultsStack.append(value)

        if questionResultsStack.count < questionsStack.count{
            self.questionLabel.text = "how \(questionsStack[questionStackArrayIndex]) are you right now?"

//mark startTime when label is changed

            self.questionStackArrayIndex++

        }
        else{
            self.performSegueWithIdentifier("showResults", sender: nil)

        }
    }

推荐答案

您可以使用NSTimeInterval来测量时间（比计时器好得多）。你只需要存储两个日期（两个时间点）并减去endTime - StartTime如下：

You can use NSTimeInterval to measure time (much better than a timer). You just need to store two dates (two points in time) and subtract endTime - StartTime as follow:

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var salesPriceSlider: UISlider!

    var startTime: NSTimeInterval = 0
    var endTime: NSTimeInterval = 0

    override func viewDidLoad() {
        super.viewDidLoad()
        startTime = NSDate().timeIntervalSinceReferenceDate
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    @IBAction func stopTimeAction(sender: AnyObject) {
        endTime = NSDate().timeIntervalSinceReferenceDate
        println((endTime-startTime).time)
    }

}

extension NSTimeInterval {
    var time: String {
        return String(format:"%d:%02d:%02d.%03d", Int(self/3600.0), Int(self/60.0 % 60), Int(self % 60), Int(self*1000 % 1000))
    }
}

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