我如何获得一个精确的时间，例如在毫秒的Objective-C？ [英] How can I get a precise time, for example in milliseconds in Objective-C?

问题描述

有一个简单的方法来得到一个时间非常精确吗？

Is there an easy way to get a time very precisely?

我需要计算方法调用之间的一些延迟。更具体地说，我想计算UIScrollView中的滚动速度。

I need to calculate some delays between method calls. More specifically, I want to calculate the speed of scrolling in an UIScrollView.

推荐答案

NSDate 并且 timeIntervalSince * 方法将返回一个 NSTimeInterval ，它是亚毫秒精度的两倍。 NSTimeInterval 以秒为单位，但它使用double来给您更高的精度。

NSDate and the timeIntervalSince* methods will return a NSTimeInterval which is a double with sub-millisecond accuracy. NSTimeInterval is in seconds, but it uses the double to give you greater precision.

为了计算毫秒时间准确度，您可以执行以下操作：

In order to calculate millisecond time accuracy, you can do:

// Get a current time for where you want to start measuring from
NSDate *date = [NSDate date];

// do work...

// Find elapsed time and convert to milliseconds
// Use (-) modifier to conversion since receiver is earlier than now
double timePassed_ms = [date timeIntervalSinceNow] * -1000.0;

关于timeIntervalSinceNow的文档。

还有很多其他方法使用 NSDate 来计算这个间隔，我建议您查看 NSDate ，位于 NSDate类参考

There are many other ways to calculate this interval using NSDate, and I would recommend looking at the class documentation for NSDate which is found in NSDate Class Reference.

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