如何获得精确的时间，例如在 Objective-C 中以毫秒为单位? [英] How can I get a precise time, for example in milliseconds in Objective-C?

问题描述

有没有一种简单的方法可以非常精确地获取时间?

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 和 timeIntervalSince* 方法将返回一个 NSTimeInterval具有亚毫秒精度的双精度值.NSTimeInterval 以秒为单位，但它使用双精度来为您提供更高的精度.

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.

为了计算毫秒时间精度，你可以这样做:

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;

有关 timeIntervalSinceNow 的文档.

还有许多其他方法可以使用 NSDate 计算此间隔，我建议查看 NSDate 的类文档，该文档位于 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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