gistfile1.m

ORSSerialRequest *request = 
    [ORSSerialRequest requestWithDataToSend:requestData
                                   userInfo:nil
                            timeoutInterval:2.0
                          responseEvaluator:^BOOL(NSData *inputData) {
                              if ([inputData length] != 8) return NO;
                              NSData *headerData = [inputData subdataWithRange:NSMakeRange(0, 4)];
                              NSString *header = [[NSString alloc] initWithData:headerData encoding:NSASCIIStringEncoding];
                              return [header isEqualToString:@"data"];
                          }];

gistfile2.swift

let request = ORSSerialRequest(dataToSend: NSData!, userInfo: nil, timeoutInterval: 2.0, 
    responseEvaluator: (inputData: NSData!) in { return true})