find the distance between two CG points?

Question

I am using these methods and these variables

CGPoint touchBegan;
CGPoint touchEnd;

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

}

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{

}

- (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

}

But I can not get the distance between two points. For example draw a line with your finger and get the distance between a CGPoint touchBegan and CGPoint touchEnd

Any help is appreciated thanks

Answer 1

It doesn't seem to exist any method or function that do this directly, you must take the difference of the two points coordinates and use pythagorean theorem:

CGPoint touchBegan;
CGPoint touchEnd;

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch* touch= [touches anyObject];
    touchBegan= [touch locationInView: self.view];
}

- (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch* touch= [touches anyObject];
    touchEnd= [touch locationInView: self.view];
    CGFloat dx= touchBegan.x - touchEnd.x;
    CGFloat dy= touchBegan.y - touchEnd.y;
    CGFloat distance= sqrt(dx*dx + dy*dy);
    < Do stuff with distance >
}

Answer 2

Just implement your own rendition of the Pythagorean theorem. For example:

CGPoint translation = CGPointMake(endPoint.x - startPoint.x, endPoint.y - startPoint.y);
CGFloat distance = sqrtf(translation.x * translation.x + translation.y * translation.y);

Or, better, as Rob Mayoff pointed out, use the Math.h hypotf method:

CGFloat distance = hypotf(translation.x, translation.y);