Have a fixed hinge while using CGAffineTransform - swift

Question

I'm using CGAffineTransform to rotate a collectionView cell. The rotation hinge is located in the bottom-left. As you can see in the images, here is how it looks
The moving progress
The issue is, I want it to rotate exactly on bottom-left`, like a fixed hinge, but now its corner is moved a bit while it's rotating.
here is my code
private func setupGestures() {
let swipeToLeft = UISwipeGestureRecognizer(target: self, action: #selector(respondToSwipeLeft))
swipeToLeft.direction = .left
container.addGestureRecognizer(swipeToLeft)
}
#objc func respondToSwipeLeft(gesture: UIGestureRecognizer) {
UIView.animate(withDuration: 0.6, animations: { [weak self] in
guard let this = self else { return }
this.backgroundView.backgroundColor = UIColor.systemRed
this.container.setAnchorPoint(anchorPoint: .init(x: 0, y: 1))
this.container.transform = CGAffineTransform(rotationAngle: -30.degreesToRadians)
haptic.impactOccurred()
}, completion: { [weak self] _ in
guard let this = self else { return }
this.rotateContainerToInitialPosition()
})
}
private func rotateContainerToInitialPosition() {
UIView.animate(withDuration: 0.6) {
self.container.transform = .identity
self.container.setAnchorPoint(anchorPoint: .init(x: 0.5, y: 0.5))
self.backgroundView.backgroundColor = UIColor.background
}
}
and
extension UIView{
func setAnchorPoint(anchorPoint: CGPoint) {
var newPoint = CGPoint(x: self.bounds.size.width * anchorPoint.x, y: self.bounds.size.height * anchorPoint.y)
var oldPoint = CGPoint(x: self.bounds.size.width * self.layer.anchorPoint.x, y: self.bounds.size.height * self.layer.anchorPoint.y)
newPoint = newPoint.applying(self.transform)
oldPoint = oldPoint.applying(self.transform)
var position : CGPoint = self.layer.position
position.x -= oldPoint.x
position.x += newPoint.x;
position.y -= oldPoint.y;
position.y += newPoint.y;
self.layer.position = position;
self.layer.anchorPoint = anchorPoint;
}
}
Your help and suggestions will be greatly appreciated.