About the problem of multi-touch

I want to on the screen, click through two fingers were detected coordinates of the two points, I was doing:

if ([touches count] == ​​2)
{
NSArray * twoTouches = [touches allObjects];
UITouch * first = [twoTouches objectAtIndex: 0];
UITouch * second = [twoTouches objectAtIndex: 1];
firstTouch = [first locationInView: self.view];
secondTouch = [second locationInView: self.view];
}

However, my question is only when the two fingers on the screen while moving when it is able to detect the coordinates, how can one finger without moving a finger move another time, able to detect multi-touch it? and most important question is , I took two coordinates which can not distinguish between the fingers, example: The first time I was taking a finger to firstTouch, b finger take to secondTouch, while the second is to take a finger to secondTouch, b finger take to firstTouch . My situation is this, who can help me? Greatly appreciated.

My qq: 312637506. I hope experts can enlighten me ~
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