UISwipeGestureRecognizer的方向设定上的坑

今天，我在用UISwipeGestureRecognizer滑动控制器的根view的时候，发现无论往哪个方向轻扫，打印swipeGestureRecognizer.direction的值都是3.
下面是我以前的代码：
UISwipeGestureRecognizer *swipeGestureRecognizer =[[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe:)];
// 轻扫手势的direction默认就是UISwipeGestureRecognizerDirectionRight swipeGestureRecognizer.direction = UISwipeGestureRecognizerDirectionRight | UISwipeGestureRecognizerDirectionLeft；
[self.view addGestureRecognizer:swipeGestureRecognizer];
这是错误的。

正确的用法：要创建两个轻扫手势，分别设定其轻扫方向才是正确的。
// 添加向左轻扫手势
UISwipeGestureRecognizer *swipeGestureRecognizerLeft = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe:)];
[self.view addGestureRecognizer:swipeGestureRecognizerLeft];
swipeGestureRecognizerLeft.direction = UISwipeGestureRecognizerDirectionLeft;

// 添加向右轻扫手势
UISwipeGestureRecognizer *swipeGestureRecognizerRight = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe:)];
[self.view addGestureRecognizer:swipeGestureRecognizerRight];
swipeGestureRecognizerRight.direction = UISwipeGestureRecognizerDirectionRight;

// 监听手势的方法

• (void)swip:(UISwipeGestureRecognizer *)sender {
  NSLog(@"%ld", sender.direction); // 判断轻扫手势的方向
  }