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iOS开发之NSDateFormatter的NSLocale使用en_US_POSIX还是en_US

iOS SDK提供的日期时间格式化对象需要使用到NSLocale对象来控制日期和时间的显示,en_US为标准的格式往往使用的最多,但是习惯使用Java或C#的朋友会忽略掉iOS SDK提供的另一种格式en_US_POSIX,并且两种格式运行后的效果完全一样。


参考代码;

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NSDateFormatter *formatter1 = [[[NSDateFormatter alloc] init] autorelease];
[formatter1 setLocale:[[[NSLocale alloc] initWithLocaleIdentifier:@"en_US"] autorelease]];
NSDateFormatter *formatter2 = [[[NSDateFormatter alloc] init] autorelease];
[formatter2 setLocale:[[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"] autorelease]];
 
[formatter1 setDateFormat:@"yyyy/MM/dd HH:mm:ss"];
[formatter2 setDateFormat:@"yyyy/MM/dd HH:mm:ss"];
 
NSDate *date = [NSDate date];
NSLog(@"formatter1:%@",[formatter1 stringFromDate:date]);
NSLog(@"formatter2:%@",[formatter2 stringFromDate:date]);

到底使用en_US_POSIX还是en_US, Apple在SDK文档中给出了答案.

In most cases the best locale to choose is “en_US_POSIX”

因为

“en_US_POSIX” is also invariant in time (if the US, at some point in the future, changes the way it formats dates, “en_US” will change to reflect the new behaviour, but “en_US_POSIX” will not), and between machines (“en_US_POSIX” works the same on iPhone OS as it does on Mac OS X, and as it it does on other platforms).

参考链接
http://stackoverflow.com/questions/6613110/what-is-the-best-way-to-deal-with-the-nsdateformatter-locale-feature
http://developer.apple.com/library/ios/#qa/qa1480/_index.html

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