gistfile1.m

NSDictionary *rabbits = @{@"name": @"Bugs", @"color":@"#777"};

NSError *error;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:rabbits
                                                               options:NSJSONWritingPrettyPrinted
                                                                 error:&error];
NSLog(@"Pretty Printed JSON:%@", [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding]);