How to rotate iOS label and make it stick to edge of screen?

Question

I've got the following structure for example:

I want to rotate my label by 270degrees to achieve this:

via CGAffineTransform.rotated next way:

    credentialsView.text = "Developed in EVNE Developers"
    credentialsView.transform = credentialsView.transform.rotated(by: CGFloat(Double.pi / 2 * 3))

but instead of expected result i've got the following:

So, what is the correct way to rotate view without changing it's bounds to square or whatever it does, and keep leading 16px from edge of screen ?

I tried a lot of ways, including extending of UILabel to see rotation directly in storyboard, putted dat view in stackview with leading and it also doesn't helps, and etc.

Answer 1

Here is the solution which will rotate your label in an appropriate way forth and back to vertical-horizontal state. Before running the code, set constraints for your label in storyboard: leading to 16 and vertically centered.

Now check it out:

class ViewController: UIViewController {

    @IBOutlet weak var label: UILabel!
    // Your leading constraint from storyboard, initially set to 16
    @IBOutlet weak var leadingConstraint: NSLayoutConstraint!

    var isHorizontal: Bool = true
    var defaultLeftInset: CGFloat = 16.0

    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.backgroundColor = .white
        label.text = "This is my label"
        self.view.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(tapAction)))
    }

    @objc func tapAction() {
        if self.isHorizontal {
            // Here goes some magic
            // constraints do not depend on transform matrix, 
            // so we have to adjust a leading one to fit our requirements
            leadingConstraint.constant = defaultLeftInset - label.frame.width/2 + label.frame.height/2
            self.label.transform = CGAffineTransform(rotationAngle: .pi/2*3)
        }
        else {
            leadingConstraint.constant = defaultLeftInset
            self.label.transform = .identity
        }
        self.isHorizontal = !self.isHorizontal
    }
}