POST and JSON into data

gistfile1.m

- (void)postDot: (Dot*)dot completionHandler: (void (^)(NSString *error, bool success))completionHandler {
    NSString *fullURLString = [NSString stringWithFormat: @"%@dots/", self.url];
    NSURL *fullURL = [NSURL URLWithString:fullURLString];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:fullURL];
    request.HTTPMethod = @"POST";
    NSData *dotJSONData = [dot parseDotIntoJSON];
    NSUInteger length = dotJSONData.length;
    [request setValue:[NSString stringWithFormat:@"%li", length] forHTTPHeaderField:@"Content-Length"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    request.HTTPBody = dotJSONData;
    NSURLSessionDataTask *dataTask = [[NSURLSession sharedSession] dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
        if (error != nil) {
            NSLog(@"%@", error.localizedDescription);
        } else {
            NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
            if ([httpResponse isKindOfClass:[NSHTTPURLResponse class]]) {
                NSInteger statusCode = httpResponse.statusCode;
                if (statusCode >= 200 && statusCode <= 299) {
                  NSError *postError;
                  NSDictionary *successJSON = [NSJSONSerialization JSONObjectWithData:data options:0 error: &postError];
                  NSTimeInterval timestamp = [successJSON[@"time"] doubleValue] / 1000;
                  dot.timestamp = [NSDate dateWithTimeIntervalSince1970:timestamp];
                  dot.identifier = successJSON[@"dot_id"];
                  NSLog(@"Time: %@ Id: %@", dot.timestamp.description, dot.identifier);
                  completionHandler(nil, YES);
                } else {
                    NSLog(@"%@", httpResponse.description);
                }
            }
        }
    }];
    [dataTask resume];
}

- (NSData *)parseDotIntoJSON {
    NSMutableDictionary *dotJSON = [[NSMutableDictionary alloc] init];
    [dotJSON setObject:[NSNumber numberWithDouble:self.location.latitude] forKey:@"latitude"];
    [dotJSON setObject:[NSNumber numberWithDouble:self.location.longitude] forKey:@"longitude"];
    [dotJSON setObject:self.color forKey:@"color"];
    [dotJSON setObject:self.title forKey:@"title"];
    [dotJSON setObject:self.body forKey:@"body"];
    [dotJSON setObject:self.username forKey:@"username_id"];
    NSError *error;
    NSData *dataToReturn = [NSJSONSerialization dataWithJSONObject:dotJSON options:0 error: &error];
    return dataToReturn;
}