dispatch_time和dispatch_walltime有什么区别?在哪种情况下最好使用其中一种? [英] What is the difference between dispatch_time and dispatch_walltime and in what situations is better to use one or the other?

问题描述

我知道dispatch_time是根据设备时钟的时间，如果设备进入睡眠状态，时钟也将进入睡眠状态.另一方面，dipatch_walltime是根据挂钟的时间，它永远不会进入睡眠状态.我的问题是，在不同的情况下使用一种或另一种在性能方面是否有区别?有人可以给我更多细节，因为Apple文档并不详尽.

I know that dispatch_time is the time according to device clock and if the device goes to sleep the clock sleeps too. On the other hand the dipatch_walltime is time according to wall clock, which never goes to sleep. My questions is, is there any difference, performance-wise or other, to use one or the other in different situations? Can somebody give me some more details, because the Apple docs are not exhaustive.

例如，我正在编写一个以特定间隔运行的Timer类.还有余地可能是10到30秒.从性能角度考虑，我应该使用哪个dispatch_time或dispatch_walltime.

For example I'm writing a Timer class which operates on certain intervals. Also the leeway could be 10 to 30 secs. Which one should I use dispatch_time or dispatch_walltime, performance-wise.

推荐答案

dispatch_time停止运行. dispatch_walltime继续运行，因为现实世界继续运行.

dispatch_time stops running when your computer goes to sleep. dispatch_walltime continues running because the real world continues running.

因此，假设您要从现在开始1个小时执行一次操作，但是5分钟后您的计算机将进入休眠状态50分钟.然后:

So suppose you want to do an action 1 hour from now, but after 5 minutes your computer goes to sleep for 50 minutes. Then:

• dispatch_walltime将在计算机唤醒后的5分钟后的一个小时内执行.

• dispatch_walltime will execute an hour from now, 5 minutes after the computer wakes up.

dispatch_time将在计算机运行一个小时后执行，即唤醒后的55分钟(从现在起1小时50分钟).

dispatch_time will execute after the computer is running for an hour, that is 55 minutes after it wakes up, 1 hour and 50 minutes from now.

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