Getting NSDate from JSON generated by WCF REST service - xcode

Question

The following code works, but it feels dirty. Is there a more standard way to convert epoch date with offset into an NSDate?
- (NSDate *) dateFromJSONString: (NSString *) JSONString{
//expects JSON from .NET WCF Service in epoch ticks, ex:
//"timeScheduled":"\/Date(1348600140000+0100)\/"
NSString *date = [[JSONString stringByReplacingOccurrencesOfString:#"/Date(" withString:#""] stringByReplacingOccurrencesOfString:#")/" withString:#""];
NSString *offsetString = [date substringFromIndex:(date.length - 5)];
//convert to seconds
NSTimeInterval dateInterval = [date doubleValue] /1000;
//gets offset value in seconds - +0100 -> 100 -> 1 -> 3600
double offsetValue = ([offsetString doubleValue] / 100) * 60 * 60;
if ([[offsetString substringToIndex:1] isEqualToString:#"+"]) {
dateInterval = dateInterval + offsetValue;
}
else{
dateInterval = dateInterval - offsetValue;
}
NSDate *retVal = [[NSDate alloc]initWithTimeIntervalSince1970:dateInterval];
return retVal;
}

Answer 1

Try this
the original gist
#implementation NSDate (DotNetDates)
+(NSDate*) dateFromDotNet:(NSString*)stringDate{
NSDate *returnValue;
if ([stringDate isMemberOfClass:[NSNull class]]) {
returnValue=nil;
}
else {
NSInteger offset = [[NSTimeZone defaultTimeZone] secondsFromGMT];
returnValue= [[NSDate dateWithTimeIntervalSince1970:
[[stringDate substringWithRange:NSMakeRange(6, 10)] intValue]]
dateByAddingTimeInterval:offset];
}
return returnValue;
}
-(NSString*) dateToDotNet{
double timeSince1970=[self timeIntervalSince1970];
NSInteger offset = [[NSTimeZone defaultTimeZone] secondsFromGMT];
offset=offset/3600;
double nowMillis = 1000.0 * (timeSince1970);
NSString *dotNetDate=[NSString stringWithFormat:#"/Date(%.0f%+03d00)/",nowMillis,offset] ;
return dotNetDate;
}
#end

Answer 2

// /Date(-422928000000+0100)/
Docs:
DateTime values appear as JSON strings in the form of "/Date(700000+0500)/", where the first number (700000 in the example provided) is the number of milliseconds in the GMT time zone, regular (non-daylight savings) time since midnight, January 1, 1970. The number may be negative to represent earlier times. The part that consists of "+0500" in the example is optional and indicates that the time is of the Local kind - that is, should be converted to the local time zone on deserialization. If it is absent, the time is deserialized as Utc. The actual number ("0500" in this example) and its sign (+ or -) are ignored.
NSTimeInterval is always specified in seconds; it yields sub-millisecond precision over a range of 10,000 years.
+ (NSDate*) dateFromDotNet:(NSString *)stringDate{
if(stringDate==(id)[NSNull null])
return nil;
NSInteger ix0= [stringDate rangeOfString:#"("].location;
NSInteger ix1= [stringDate rangeOfString:#")"].location;
if(ix0==NSNotFound || ix1==NSNotFound)
#throw [NSException exceptionWithName:#"ExceptionName" reason:#"Invalid JSON data" userInfo:#{#"json":stringDate}];
NSRange range= NSMakeRange(ix0+1, ix1-ix0);
NSString *dateString= [stringDate substringWithRange:range];
// dateString: -422928000000+0100
NSCharacterSet *signs= [NSCharacterSet characterSetWithCharactersInString:#"+-"];
range= [dateString rangeOfCharacterFromSet:signs option:NSBackwardSearch];
// WCF will send 13 digit-long value for the time interval since 1970 (millisecond precision)
// whereas iOS works with 10 digit-long values (second precision), hence the divide by 1000
NSTimeInterval unixTime = [dateString doubleValue] / 1000;
if(range.location!=NSNotFound){
NSString *sign = [dateString substringWithRange:range];
NSString *off = [dateString substringFromIndex:range.location+1];
// gets offset value in seconds -+0100 -> 100 -> 1 -> 3600
double offset = ([off doubleValue] / 100) * 60 * 60;
if ([sign isEqualToString:#"+"])
unixTime+= offset;
else
unixTime-= offset;
}
NSDate *date= [NSDate dateWithTimeIntervalSince1970:unixTime];
return date;
}