Constraints not updating and view is letterboxed when rotating device

Question

Background:

When rotating the device, the view myView becomes letterboxed instead of resizing to fit the screen, see image below.

On the storyboard, centreX and centreY constraints are set.

In the code, width and height constraints are set with the function viewAddConstraints(), see code below.

After the device is rotated, I call viewAddConstraints() again, but Xcode gives the following error: Unable to simultaneously satisfy constraints.

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Questions:

How do I correctly remove old constraints and then add new constraints when the device is rotated?

How do I correctly update the constraints of a view when the device is rotated?

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Code:

func viewAddConstraints() {

// Width constraint full width of screen
        let myViewWidth = NSLayoutConstraint(item: myView as Any, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: view.bounds.width)
        myView.addConstraint(myViewWidth)

// Height constraint full height of screen
        let myViewHeight = NSLayoutConstraint(item: myView as Any, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: view.bounds.height)
        myView.addConstraint(myViewHeight)

}

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Image:

Current situation, view is incorrectly letterboxed.

Intended situation, view resized correctly.

Answer 1

The proper way to set constraints to keep your subview "pinned" to the sides:

override func viewDidLoad() {
    super.viewDidLoad()
    
    let myView = UIView()
    myView.backgroundColor = .systemTeal
    myView.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(myView)
    
    NSLayoutConstraint.activate([
        myView.topAnchor.constraint(equalTo: view.topAnchor),
        myView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
        myView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
        myView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
    ])
    
}

Or, since you should be respecting the Safe Area:

override func viewDidLoad() {
    super.viewDidLoad()
    
    let myView = UIView()
    myView.backgroundColor = .systemTeal
    myView.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(myView)
    
    let g = view.safeAreaLayoutGuide

    NSLayoutConstraint.activate([
        myView.topAnchor.constraint(equalTo: g.topAnchor),
        myView.leadingAnchor.constraint(equalTo: g.leadingAnchor),
        myView.trailingAnchor.constraint(equalTo: g.trailingAnchor),
        myView.bottomAnchor.constraint(equalTo: g.bottomAnchor),
    ])
    
}

Now your subview will automatically resize to fit its superview on device rotation.