Use this property to track changes to a particular touch during the touch's life.
While touch identities may be re-used, they are unique during the life of the touch, even when multiple devices are present.
Identity objects implement the
NSCopying protocol so that they may be used as keys in an
NSDictionary. Use isEqual: to compare two touch identities.
Properties of this touch
The current phase of the touch.
Returns whether the touch is a resting touch.