Very easy implementation to handle basic horizontal and vertical swipes for Unity on mobile devices

TouchController.cs

/// <summary>
/// TouchController allows you to handle basic swipes (left, right, top, bottom) on mobile device.
///
/// Usage: extend this class and don't forget to call Update in MonoBehaviour.Update
/// <summary>
public abstract class TouchController {
        private readonly float _swipeThreshold;

        private Vector2 _firstPosition;

        private Vector2 _lastPosition;

        protected TouchController(float thresholdInUnits) {
            _swipeThreshold = thresholdInUnits * Screen.dpi;
            _firstPosition = _lastPosition = Vector2.zero;
        }

        /// <summary>
        /// Call this function in MonoBehaviour.Update
        /// </summary>
        public void Update() {
            if (Input.touchCount > 0) {
                var touch = Input.GetTouch(0);

                switch (touch.phase) {
                    case TouchPhase.Began:
                        _firstPosition = _lastPosition = touch.position;
                        break;
                    case TouchPhase.Moved:
                        _lastPosition = touch.position;
                        break;
                    case TouchPhase.Ended:
                        if (Vector2.Distance(_firstPosition, _lastPosition) > _swipeThreshold) {
                            if (Mathf.Abs(_firstPosition.x - _lastPosition.x) >
                                Mathf.Abs(_firstPosition.y - _lastPosition.y)) {
                                if ((_lastPosition.x > _firstPosition.x)) {
                                    OnSwipe(MoveDirection.Left);
                                } else {
                                    OnSwipe(MoveDirection.Right);
                                }
                            } else {
                                if (_lastPosition.y > _firstPosition.y) {
                                    OnSwipe(MoveDirection.Down);
                                } else {
                                    OnSwipe(MoveDirection.Up);
                                }
                            }
                        }
                        break;
                    case TouchPhase.Canceled:
                        _firstPosition = _lastPosition = Vector2.zero;
                        break;
                }
            }
        }

        protected abstract void OnSwipe(MoveDirection direction);
}