gistfile1.m

- (void) functionWhichAnnoyinglyBlocksExecution: (NSFileHandle *) annoyingFileHandle
{
  dispatch_async(dispatch_get_global_queue(0,0), ^{
    id result = [annoyingFileHandle someBlockingOp];
    dispatch_async(dispatch_get_main_queue(), ^{
      [myController displayResult: result];
    });
  });
}