This will convert DateTime (.NET) object serialized as JSON by WCF to a NSDate object

gistfile1.m

/*
 * This will convert DateTime (.NET) object serialized as JSON by WCF to a NSDate object.
 */

// Input string is something like: "/Date(1292851800000+0100)/" where
// 1292851800000 is milliseconds since 1970 and +0100 is the timezone
NSString *inputString = [item objectForKey:@"DateTimeSession"];

// This will tell number of seconds to add according to your default timezone
// Note: if you don't care about timezone changes, just delete/comment it out
NSInteger offset = [[NSTimeZone defaultTimeZone] secondsFromGMT];

// A range of NSMakeRange(6, 10) will generate "1292851800" from "/Date(1292851800000+0100)/"
// as in example above. We crop additional three zeros, because "dateWithTimeIntervalSince1970:"
// wants seconds, not milliseconds; since 1 second is equal to 1000 milliseconds, this will work.
// Note: if you don't care about timezone changes, just chop out "dateByAddingTimeInterval:offset" part
NSDate *date = [[NSDate dateWithTimeIntervalSince1970:
                 [[inputString substringWithRange:NSMakeRange(6, 10)] intValue]]
                dateByAddingTimeInterval:offset];

// You can just stop here if all you care is a NSDate object from inputString,
// or see below on how to get a nice string representation from that date:

// static is nice if you will use same formatter again and again (for example in table cells)
static NSDateFormatter *dateFormatter = nil;
if (dateFormatter == nil) {
    dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateStyle:NSDateFormatterShortStyle];
    [dateFormatter setTimeStyle:NSDateFormatterNoStyle];

    // If you're okay with the default NSDateFormatterShortStyle then comment out two lines below
    // or if you want four digit year, then this will do it:
    NSString *fourDigitYearFormat = [[dateFormatter dateFormat]
                                     stringByReplacingOccurrencesOfString:@"yy"
                                     withString:@"yyyy"];
    [dateFormatter setDateFormat:fourDigitYearFormat];
}

// There you have it:
NSString *outputString = [dateFormatter stringFromDate:date];

doesn't this fail for dates earlier than Sun, 09 Sep 2001 01:46:40 GMT as the unix timestamp is only 9 characters (so you will read an extra 0 and have a massive error)?

@tristandl thanks a lot for you comment and excuse me for late reply. My code worked at the time for which I needed for, but I don't pretend it to be perfect. Are you just guessing or did you actually encountered this problem? If you think you can fix it any patches are very welcome. Regards.

If the date is pre 2001 it will be less than 10 characters, and you will accidentally consume one of the trailing 0's. I appreciate you want to keep it lean and not parse the whole string to find the end of the text, see my fork for my modification where I look for the start of the number, and use doubleValue which reads the string up to the ), + or - character and divide by 1000 to get time in seconds.

In my project I removed the timezone stuff and format for locales in the UI, but that's up to you

@tristandl since I don't have time to try this I'll take your word about pre 2001 less than 10 chars issue and I'll agree with you. I knew a range of (6, 10) was just an ugly hack to do this, but I assumed JSON string was always "that much long"... Soonish I will create a repo for this and put some other little things of mine for Objective-C language, so I will get serious&deeper on this. Your fix, one way or another, will definitely be there. Thank a lot!

Check out also RestKit/RestKit#264

@exalted Thank you very much, it really helped me !

@Ded77 you're welcome... ;-)