UISwipeGestureRecognizer is a concrete subclass of UIGestureRecognizer that looks for swiping gestures in one or more directions. A swipe is a discrete gesture, and thus the associated action message is sent only once per gesture.
UISwipeGestureRecognizer recognizes a swipe when the specified number of touches (numberOfTouchesRequired) have moved mostly in an allowable direction (direction) far enough to be considered a swipe. Swipes can be slow or fast. A slow swipe requires high directional precision but a small distance; a fast swipe requires low directional precision but a large distance.
You may determine the location where a swipe began by calling the UIGestureRecognizer methods locationInView: and locationOfTouch:inView:. The former method gives you the centroid if more than one touch was involved in the gesture; the latter gives the location of a particular touch.
Whole document - UISwipeGestureRecognizer
