title: Couldn't get UISwipeGestureRecognizer direction correctly
body: <p>I'm writing code to move my two fingers up or down on a view to change some status. The code as below:</p>
  
  <pre><code>UISwipeGestureRecognizer *aSwipeGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipeGesture:)];
  [aSwipeGesture setDirection:UISwipeGestureRecognizerDirectionUp | UISwipeGestureRecognizerDirectionDown];
  aSwipeGesture.numberOfTouchesRequired = 2;
  [self.View addGestureRecognizer:aSwipeGesture];
  
  
  - (void)swipeGesture:(UISwipeGestureRecognizer *)sender {
      NSLog(@"Swipe received.");
      if (sender.direction==UISwipeGestureRecognizerDirectionUp) {
          NSLog(@"swipe up");
      } else if (sender.direction==UISwipeGestureRecognizerDirectionDown) {
          NSLog(@"swipe down");
      }
  }
  </code></pre>
  
  <p>However the only print log I could receive was Swipe received as below shows. I couldn't get the message for swipe up or swipe down, did I miss anything? Thanks</p>
  
  <pre><code>ViewController.m:228    Swipe received.
  ViewController.m:228    Swipe received.
  ViewController.m:228    Swipe received.
  ViewController.m:228    Swipe received.
  ViewController.m:228    Swipe received.
  ViewController.m:228    Swipe received.
  </code></pre>
  
  <p>Updated: I have to use two fingers to finish the swipe action.</p>