Blog - Hamburger Menu on iOS Done Right - gestureScreenEdgePan Selector

gestureScreenEdgePan Selector

@IBAction func gestureScreenEdgePan(_ sender: UIScreenEdgePanGestureRecognizer) {
      
      // retrieve the current state of the gesture
      if sender.state == UIGestureRecognizerState.began {

          // if the user has just started dragging, make sure view for dimming effect is hidden well
          viewBlack.isHidden = false
          viewBlack.alpha = 0
      } else if (sender.state == UIGestureRecognizerState.changed) {

          // retrieve the amount viewMenu has been dragged
          let translationX = sender.translation(in: sender.view).x
          if -constraintMenuWidth.constant + translationX > 0 {

              // viewMenu fully dragged out
              constraintMenuLeft.constant = 0
              viewBlack.alpha = maxBlackViewAlpha
          } else if translationX < 0 {

              // viewMenu fully dragged in
              constraintMenuLeft.constant = -constraintMenuWidth.constant
              viewBlack.alpha = 0
          } else {

              // viewMenu is being dragged somewhere between min and max amount
              constraintMenuLeft.constant = -constraintMenuWidth.constant + translationX

              let ratio = translationX / constraintMenuWidth.constant
              let alphaValue = ratio * maxBlackViewAlpha
              viewBlack.alpha = alphaValue
          }
      } else {

          // if the menu was dragged less than half of it's width, close it. Otherwise, open it.
          if constraintMenuLeft.constant < -constraintMenuWidth.constant / 2 {
              self.hideMenu()
          } else {
              self.openMenu()
          }
      }
}