Nslog时间戳 [英] Nslog timestamp

问题描述

我想对设备运动时间戳属性进行nslog记录.

I want to nslog the device motion timestamp property .

设备运动位于CMMotionManager.devicemotion.timestamp类中

The device motion is in the class CMMotionManager.devicemotion.timestamp

任何想法.

推荐答案

编辑:请参阅Nicolas Lauquin的回答.根据评论，以下解决方案不正确，但保留在此处以作历史记录(并且由于无法将其删除，因为它目前被标记为接受).

Edit: Please see Nicolas Lauquin's answer. Per the comments, the following solution is not correct but is retained here for history (and because I can't delete it since it is currently marked accepted).

timestamp 属性是一个 NSTimeInterval ，因此您应该可以:

The timestamp property is an NSTimeInterval, so you should be able to do:

NSLog(@"Motion at time: %@",
[NSDate dateWithTimeIntervalSinceReferenceDate:devicemotion.timestamp]);

NSTimeInterval 只是类型定义的 double 类型，因此您可以使用％f 而不是％@ 并直接记录.

NSTimeInterval is just a typedef'd double type, so you could use %f instead of %@ and log it directly.

此外，文档未指出此时间戳是针对Apple的参考日期还是标准的* nix日期设置的，因此，如果上述方法返回，则可能需要使用 [NSDate dateWithTimeIntervalSince1970:] 日期远在未来.

Also, the docs don't indicate whether this timestamp is set against Apple's reference date or the standard *nix date, so you may need to use [NSDate dateWithTimeIntervalSince1970:] if the aforementioned method returns dates far in the future.

由于@davidbitton建议 CMDeviceMotion 的 timestamp 与上次设备启动有关，因此正确的 NSDate 可以由

As @davidbitton has suggested the CMDeviceMotion's timestamp is relative to the last device boot, the correct NSDate could be derived by

NSDate *startupTime = [NSDate dateWithTimeIntervalSinceNow:
                          -1 * [[NSProcessInfo processInfo] systemUptime]];

NSDate *deviceMotionDate = [NSDate dateWithTimeInterval:devicemotion.timestamp 
                                              sinceDate:startupTime];

假设@davidbitton是正确的，这应该产生一个大致准确的 NSDate 对象.(参考:

This should yield a roughly accurate NSDate object, assuming @davidbitton is correct. (reference: NSProcessInfo -systemUptime)

但是，鉴于这有多么复杂，我现在为简单起见建议，考虑到 timestamp 属性的性质，您可以将其记录为格式字符串，例如

However, given how complicated this is, I would now suggest for simplicity that, given the nature of the timestamp property, that you log it in a format string as something like

"... event logged at %0.2f seconds since startup...", devicemotion.timestamp

这篇关于Nslog时间戳的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！