Why is longLongValue returning the incorrect value

Question

I have a NSDictionary that contains a key with a value of 4937446359977427944. I try and get the value of it as a long long and get 4937446359977427968 back?

Answer 1

For anyone interested in quick solution to the problem, as per Analog File proper answer:

long long someNumber = 8204064638523577098;
NSLog(@"some number lld:               %lld", someNumber);
NSNumber *snNSNumber = [NSNumber numberWithLongLong:someNumber];
NSLog(@"some number NSNumber:          %@", snNSNumber);
NSString *someJson = @"{\"someValue\":8204064638523577098}";
NSDictionary* dict = [NSJSONSerialization
 JSONObjectWithData:[someJson dataUsingEncoding:NSUTF8StringEncoding]
 options:0
 error:nil];
NSLog(@"Dict: %@", dict);
NSLog(@"Some digit out of dict:        %@", [dict objectForKey:@"someValue"]);
NSLog(@"Some digit out of dict as lld: %lld", [[dict objectForKey:@"someValue"] longLongValue]);
long long someNumberParsed;
sscanf([[[dict objectForKey:@"someValue"] stringValue] UTF8String], "%lld", &someNumberParsed);
NSLog(@"Properly parsed lld:           %lld", someNumberParsed);

Results in:

2014-04-16 14:22:02.997 Tutorial4[97950:303] some number lld:
8204064638523577098

2014-04-16 14:22:02.998 Tutorial4[97950:303] some number NSNumber:
8204064638523577098

2014-04-16 14:22:02.998 Tutorial4[97950:303] Dict: { someValue = 8204064638523577098; }

2014-04-16 14:22:02.998 Tutorial4[97950:303] Some digit out of dict:
8204064638523577098

2014-04-16 14:22:02.999 Tutorial4[97950:303] Some digit out of dict as lld: 8204064638523577344

2014-04-16 14:22:02.999 Tutorial4[97950:303] Properly parsed lld:
8204064638523577098