// from StackOverflow
CAShapeLayer *layer = [CAShapeLayer layer];
UIBezierPath *linePath = [UIBezierPath bezierPath];
[linePath moveToPoint: pointA];
[linePath addLineToPoint: pointB];
line.path = linePath.CGPath;
line.fillColor = nil;
line.opacity = 1.0;
line.strokeColor = [UIColor redColor].CGColor;
[layer addSublayer:line];
