在Objective-C中解析ISO8601日期（iPhone OS SDK）

Question

How do I parse "2010-04-30T00:45:48.711127" into an NSDate? (and maintain all precision)

Answer 1

You have your work cut out for you.

NSDate will throw out any values past 3 decimal places for seconds. You can create a subclass of NSDate to hold on to that precision but you'll also need to implement your own parsing and custom formatters to input and display it since NSDateFormatter and CFDateFormatter , which it is built on, will also truncate precision after 3 decimal places. Depending on what you're doing though that shouldn't be all that hard.

This is a simple subclass (not implementing NSCoding or NSCopying ) that will hold on to all the precision you give it.

@interface RMPreciseDate : NSDate {
    double secondsFromAbsoluteTime;
}

@end

@implementation RMPreciseDate

- (NSTimeInterval)timeIntervalSinceReferenceDate {
    return secondsFromAbsoluteTime;
}

- (id)initWithTimeIntervalSinceReferenceDate:(NSTimeInterval)secsToBeAdded {
    if (!(self = [super init]))
        return nil;

    secondsFromAbsoluteTime = secsToBeAdded;

    return self;
}

@end

You can then ask for the -timeIntervalSince1970 to get UNIX epoch time.

There is an ISO8601 date/time parser class already out there, but since it's using NSDateComponents to generate its date it's limited to full-second precision currently, but you could use it as a starting point perhaps to create more precise representations.

Answer 2

我打算尝试这个ISO 8601解析器和类似情况下的解析器： http ：//boredzo.org/iso8601parser/

Answer 3

It seems the NSDate only has millisecond precision.

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"yyyy-MM-dd'T'hh:mm:ss.SSSSSS"];

    NSDate *date = [dateFormatter dateFromString:@"2010-04-30T00:45:48.711127"];

    NSLog(@"%@", date);

    NSString *string = [dateFormatter stringFromDate:date];

    NSLog(@"%@", string);

    [pool drain];
    return 0;
}

That code yields the following console output:

Program loaded.
run
[Switching to process 27202]
Running…
2010-05-08 20:02:46.342 TestNSDate[27202:a0f] 2010-04-30 00:45:48 -0700
2010-05-08 20:02:46.344 TestNSDate[27202:a0f] 2010-04-30T12:45:48.711000

Debugger stopped.
Program exited with status value:0.

So "2010-04-30T00:45:48.711127" turning into "2010-04-30T00:45:48.711000" is probably not what you have in mind.