Nil NSDate试图在祖鲁时间从UTC字符串获取日期 [英] Nil NSDate when trying to get date from UTC string in zulu time

问题描述

在Objective-C中编写一个iPhone应用程序，我有一个字符串形式的日期（UTC格式，最后用Z表示零UTC偏移，或祖鲁时间），我需要解析为 NSDate object。


一些代码：

Writing an iPhone app in Objective-C, I have a date in string form (in UTC format, with a Z on the end to denote zero UTC offset, or zulu time), which I need to parse into an NSDate object.

A bit of code:

NSDateFormatter* df = [[NSDateFormatter alloc]init];
[df setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss.SSSZ"];
NSString* str = @"2009-08-11T06:00:00.000Z";
NSDate* date = [df dateFromString:str];

通过调试器运行， date 结束 nil ！我假设它与我的日期格式字符串有关。

如何修复它以正确解析日期字符串？


想到的是日期格式文字中的 Z ，将日期格式设置为 yyyy-MM-dd'T'HH：mm：ss.SSS'Z '。


这样可行，除非将Z解析为文字，日期会丢失偏移信息，因此不明确，因此被解释为本地时间。


例如，如果要解析的字符串是2009-08-11T06：00：00.000Z（6:00祖鲁时间），则会被解释为当地时间的6:00，并且然后将应用不正确的偏移。然后将其解析为2009-08-11T06：00：00.000-600（12:00祖鲁时间），偏移量取决于用户的偏移量。


谢谢！

Running this through the debugger, date ends up nil! I'm assuming it has something to do with my date format string.

How can I fix it to correctly parse the date string?

A thought would be to make the Z in the date format literal, a la setting the date format to yyyy-MM-dd'T'HH:mm:ss.SSS'Z'.

That would work, except when the Z is parsed as a literal, the date loses offset information, and so is ambiguous, and therefore interpreted to be local time.

For example, if the string to parse was 2009-08-11T06:00:00.000Z (6:00 zulu time) it would be interpreted as 6:00 local time, and an incorrect offset would then be applied. It would then be parsed as 2009-08-11T06:00:00.000-600 (12:00 zulu time) with the offset depending on the user's offset.

Thanks!

推荐答案

我也有这个问题，我不确定这是Apple代码中的API错误，还是我缺乏理解，但我通过在我的日期字符串中使用小时偏移来解决这个问题。

I've had this problem also, I'm not sure if it's a API bug within Apple's code, or my lack of understanding, but I've worked around it by using hour offsets in my date strings.

如果您将示例中的代码更改为：

If you change the code in your example to:

NSDateFormatter* df = [[NSDateFormatter alloc]init];
[df setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss.SSSZ"];
NSString* str = @"2009-08-11T06:00:00.000-0700";   // NOTE -0700 is the only change
NSDate* date = [df dateFromString:str];

它现在将解析日期字符串。当然-0700小时是我的抵消，你必须把它改成你的。希望这会有所帮助。

It will now parse the date string. Of course the -0700 hours is my offset, you'd have to change it to yours. Hope this helps.

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