不知道如何将触摸作为单个实体来处理

I have a game for iPad where two different players may interact with the environment at the same time. When the game is played by two people in the same device at once I have a problem that I don't know how to solve. I want the game to behave in the next way: when a player touches a sprite, and finishes the touch in another sprite the app must be able to know that it has been the same player who did it. I have a game for iPad where two different play