在Swift中测量经过时间

这是我编写的用于测量Swift中的Euler问题的Swift函数

从Swift 3开始，Grand Central Dispatch现在有一个“精简版”版本。因此正确的答案可能是使用DispatchTime
API
。

我的函数看起来像：

// Swift 3func evaluateProblem(problemNumber: Int, problemBlock: () -> Int) -> Answer{    print("evaluating problem (problemNumber)")    let start = DispatchTime.now() // <<<<<<<<<< Start time    let myGuess = problemBlock()    let end = DispatchTime.now()   // <<<<<<<<<<   end time    let theAnswer = self.checkAnswer(answerNum: "(problemNumber)", guess: myGuess)    let nanoTime = end.uptimeNanoseconds - start.uptimeNanoseconds // <<<<< Difference in nano seconds (UInt64)    let timeInterval = Double(nanoTime) / 1_000_000_000 // Technically could overflow for long running tests    print("Time to evaluate problem (problemNumber): (timeInterval) seconds")    return theAnswer}

旧答案

对于Swift 1和2，我的函数使用NSDate：

// Swift 1func evaluateProblem(problemNumber: Int, problemBlock: () -> Int) -> Answer{    println("evaluating problem (problemNumber)")    let start = NSDate() // <<<<<<<<<< Start time    let myGuess = problemBlock()    let end = NSDate()   // <<<<<<<<<<   end time    let theAnswer = self.checkAnswer(answerNum: "(problemNumber)", guess: myGuess)    let timeInterval: Double = end.timeIntervalSinceDate(start) // <<<<< Difference in seconds (double)    println("Time to evaluate problem (problemNumber): (timeInterval) seconds")    return theAnswer}

请注意，不建议将NSdate用于计时功能：“ 由于与外部时间参考同步或由于用户明确更改了时钟，因此系统时间可能会减少。 ”。