Parsing JSON dates on IPhone - iphone

Question

Forgive me as I'm new to Objective C.
I am getting back dates from a .NET webservice in the /Date(xxxxxxxxxxxxx-xxxx)/ format. I'm looking for some direction on how to best parse this into an NSDate object. I've tried using dateWithTimeIntervalSince1970 on it but it comes back with a date in the year 1969 for a date I know is in 2006.
Looking for some direction on the proper way to handle JSON dates.
Thanks in advance!

Answer 1

I just wrote this for iOS 4.0+ (because it uses NSRegularExpression). It handles dates with or without timezone offsets. Seems to work pretty well, what do you think?
+ (NSDate *)mfDateFromDotNetJSONString:(NSString *)string {
static NSRegularExpression *dateRegEx = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
dateRegEx = [[NSRegularExpression alloc] initWithPattern:#"^\\/date\\((-?\\d++)(?:([+-])(\\d{2})(\\d{2}))?\\)\\/$" options:NSRegularExpressionCaseInsensitive error:nil];
});
NSTextCheckingResult *regexResult = [dateRegEx firstMatchInString:string options:0 range:NSMakeRange(0, [string length])];
if (regexResult) {
// milliseconds
NSTimeInterval seconds = [[string substringWithRange:[regexResult rangeAtIndex:1]] doubleValue] / 1000.0;
// timezone offset
if ([regexResult rangeAtIndex:2].location != NSNotFound) {
NSString *sign = [string substringWithRange:[regexResult rangeAtIndex:2]];
// hours
seconds += [[NSString stringWithFormat:#"%#%#", sign, [string substringWithRange:[regexResult rangeAtIndex:3]]] doubleValue] * 60.0 * 60.0;
// minutes
seconds += [[NSString stringWithFormat:#"%#%#", sign, [string substringWithRange:[regexResult rangeAtIndex:4]]] doubleValue] * 60.0;
}
return [NSDate dateWithTimeIntervalSince1970:seconds];
}
return nil;
}

Answer 2

I was in the same boat whilst using json-framework which doesn't support the date format as it's not official JSON. My source is from an API built using JSON.Net. This is what I came up with:
- (NSDate*) getDateFromJSON:(NSString *)dateString
{
// Expect date in this format "/Date(1268123281843)/"
int startPos = [dateString rangeOfString:#"("].location+1;
int endPos = [dateString rangeOfString:#")"].location;
NSRange range = NSMakeRange(startPos,endPos-startPos);
unsigned long long milliseconds = [[dateString substringWithRange:range] longLongValue];
NSLog(#"%llu",milliseconds);
NSTimeInterval interval = milliseconds/1000;
return [NSDate dateWithTimeIntervalSince1970:interval];
}
I don't have the appended portion in the date format that you do so I haven't dealt with that like the answer above. No error catching either, it's all new to me at this point.

Answer 3

I actually found the snippet with NSRegularExpression pretty useful, till i came up with another solution that uses NSCharecterSet for stipping off the milliseconds.
+ (NSDate*) dateFromJSONString:(NSString *)dateString
{
NSCharacterSet *charactersToRemove = [[ NSCharacterSet decimalDigitCharacterSet ] invertedSet ];
NSString* milliseconds = [dateString stringByTrimmingCharactersInSet:charactersToRemove];
if (milliseconds != nil && ![milliseconds isEqualToString:#"62135596800000"]) {
NSTimeInterval seconds = [milliseconds doubleValue] / 1000;
return [NSDate dateWithTimeIntervalSince1970:seconds];
}
return nil;
}
Saves a lot of the manual string processing and makes the code much cleaner.

Answer 4

As a .NET programmer learning Objective-C I had the same problem when I tried to consume a .Net WebService.
At first I thought I would be able to use the NSDateFormatter...
I found a really good reference for it's symbols here, but I quickly realized that I needed to convert the number from milliseconds to seconds.
I wrote the code to do it...
I'm still learning Obj-C but I dont think It should've been this hard...
- (NSDate *) getJSONDate{
NSString* header = #"/Date(";
uint headerLength = [header length];
NSString* timestampString;
NSScanner* scanner = [[NSScanner alloc] initWithString:self];
[scanner setScanLocation:headerLength];
[scanner scanUpToString:#")" intoString:&timestampString];
NSCharacterSet* timezoneDelimiter = [NSCharacterSet characterSetWithCharactersInString:#"+-"];
NSRange rangeOfTimezoneSymbol = [timestampString rangeOfCharacterFromSet:timezoneDelimiter];
[scanner dealloc];
if (rangeOfTimezoneSymbol.length!=0) {
scanner = [[NSScanner alloc] initWithString:timestampString];
NSRange rangeOfFirstNumber;
rangeOfFirstNumber.location = 0;
rangeOfFirstNumber.length = rangeOfTimezoneSymbol.location;
NSRange rangeOfSecondNumber;
rangeOfSecondNumber.location = rangeOfTimezoneSymbol.location + 1;
rangeOfSecondNumber.length = [timestampString length] - rangeOfSecondNumber.location;
NSString* firstNumberString = [timestampString substringWithRange:rangeOfFirstNumber];
NSString* secondNumberString = [timestampString substringWithRange:rangeOfSecondNumber];
unsigned long long firstNumber = [firstNumberString longLongValue];
uint secondNumber = [secondNumberString intValue];
NSTimeInterval interval = firstNumber/1000;
return [NSDate dateWithTimeIntervalSince1970:interval];
}
unsigned long long firstNumber = [timestampString longLongValue];
NSTimeInterval interval = firstNumber/1000;
return [NSDate dateWithTimeIntervalSince1970:interval];
}
Hopefully someone can provide a better Obj-C solution.
If not I may keep this or look for a way to change the serialization format in .NET
EDIT:
About that JSON DateTime format...
If you have any control on the service it would probably be best to convert the date to a string in your DataContract objects.
Formatting to RFC1123 seems like a good idea to me right now. As I can probably pick it up easily using a NSDateFormatter.
Quote from Rick Strahl
There's no JavaScript date literal and Microsoft engineered a custom date format that is essentially a marked up string. The format is a string that's encoded and contains the standard new Date(milliseconds since 1970) value.

Answer 5

Theory: MS encoded the C# DateTime in JSON as milliseconds since 1970.
Solution:
NSString*
dateAsString = #"/Date(1353720343336+0000)/";
dateAsString = [dateAsString stringByReplacingOccurrencesOfString:#"/Date("
withString:#""];
dateAsString = [dateAsString stringByReplacingOccurrencesOfString:#"+0000)/"
withString:#""];
unsigned long long milliseconds = [dateAsString longLongValue];
NSTimeInterval interval = milliseconds/1000;
NSDate* date = [NSDate dateWithTimeIntervalSince1970:interval];
This is the shortest solution I can think of.

Answer 6

Use an NSDateFormatter's dateFromString: method after setting the date format.

Answer 7

-(NSString*)convertToUTCTime:(NSString*)strDate{
NSDate *currentDate = [NSDate date];
myDate = [commonDateFormatter dateFromString: strDate];
NSTimeInterval distanceBetweenDates = [currentDate timeIntervalSinceDate:myDate];
return [self stringFromTimeInterval:distanceBetweenDates];
}
- (NSString *)stringFromTimeInterval:(NSTimeInterval)interval {
NSInteger ti = (NSInteger)interval;
NSInteger minutes = (ti / 60) % 60;
NSInteger hours = (ti / 3600);
if (hours > 24) {
NSInteger days = hours/24;
if (days > 30) {
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"EEE d MMM, h:mm a"];
//[dateFormatter setTimeZone:[NSTimeZone timeZoneWithName:#"IST"]];
NSString *daydate = [dateFormatter stringFromDate:myDate];
return daydate;
}
else{
return [NSString stringWithFormat:#" %2ldd",(long)days];
}
}else{
if (hours == 0 && minutes < 1) {
return [NSString stringWithFormat:#"Today"];
}
else if (hours == 0 && minutes < 60){
return [NSString stringWithFormat:#"%2ldm ",(long)minutes];
}
else{
return [NSString stringWithFormat:#" %2ldh",(long)hours];
}
}
}