Swift default AlertViewController breaking constraints

Question

I am trying to use a default AlertViewController with style .actionSheet. For some reason, the alert causes a constraint error. As long as

Answer 1

If you want to keep animation and all constraints, you should find a negative constraint and make it positive before presenting alert controller.

// Find negative constraint and make it positive
for subview in alert.view.subviews {
    for constraint in subview.constraints {
        if constraint.constant < 0 {
            constraint.constant = -constraint.constant
        }
    }
}

// Present alert controller
present(alert, animated: true)

Answer 2

This error is not critical, seems to be unfixed bug form Apple. This constraint appears in animation style just after presenting. I tried to catch and change it (change values, relations, priority) before presenting – no success because of this dynamically added constraints.

When you turn off animation in self.present(alert, animated: false) and using alert.view.addSubview(UIView()) – the error disappears. I can't explain it, but it works!

let alert = UIAlertController(title: "Change your profile image", message: nil, preferredStyle: .actionSheet)

alert.addAction(UIAlertAction(title: "Photo Library", style: .default, handler: nil))
alert.addAction(UIAlertAction(title: "Online Stock Library", style: .default, handler: nil))
let cancel = UIAlertAction(title: "Cancel", style: .destructive, handler: nil)

alert.addAction(cancel)
alert.view.addSubview(UIView()) // I can't explain it, but it works!

self.present(alert, animated: false)

Answer 3

Adding to this answer...This seems to remove the issue for me and doesn't require any changes to existing code.

extension UIAlertController {
    override open func viewDidLoad() {
        super.viewDidLoad()
        pruneNegativeWidthConstraints()
    }

    func pruneNegativeWidthConstraints() {
        for subView in self.view.subviews {
            for constraint in subView.constraints where constraint.debugDescription.contains("width == - 16") {
                subView.removeConstraint(constraint)
            }
        }
    }
}