What is the best way to rotate a CGPoint on a grid?

Question

I want to rotate a CGPoint on the screen depending on the angle and the rotation is anchored on another point. Was wondering what is the most efficient way of doing this?

Answer 1

Swift 5

extension CGPoint {
    func rotate(around center: CGPoint, angle: CGFloat) -> CGPoint {
        let translate = CGAffineTransform(translationX: -center.x, y: -center.y)
        let transform = translate.concatenating(CGAffineTransform(rotationAngle: angle))
        let rotated = applying(transform)
        return rotated.applying(CGAffineTransform(translationX: center.x, y: center.y))
    }
}