Question

[CATransaction begin];
            [CATransaction setAnimationDuration:5];
            CGAffineTransform currentTransform = squareLayer.affineTransform;
            CGFloat angle = M_PI;

            squareLayer.affineTransform = CGAffineTransformRotate(currentTransform, angle);
            [CATransaction commit];

and

[CATransaction begin];
            [CATransaction setAnimationDuration:5];
            CGAffineTransform currentTransform = squareLayer.affineTransform;
            CGFloat angle = (M_PI * -1);

            squareLayer.affineTransform = CGAffineTransformRotate(currentTransform, angle);
            [CATransaction commit];

I would have thought the -1 would have reversed the direction but apparently not?

Answer 1

The angle is the same. To go full circle you need 2 * Pi, so half a circle is Pi. If you take -Pi it would end at the same point.

EDIT: If you need to make it turn clockwise you can go slightly off -Pi. Instead of -M_PI use -3.141593 for example.