Swift ImagePicker在AutoLayout约束上引发SIGNAL SIGABRT

Question

I'm building a project in Swift5 and I need the user to upload a photo. I have it to the point where the user can open the ImagePicker and select a photo, but whenever they select the image and return to the original VC, I get a SIGNAL SIGABRT error (at bottom of post):

Here is where I add my constraints programatically:

func setupLayout(){
    imgView.topAnchor.constraint(equalTo: view.topAnchor, constant: 150).isActive = true
    imgView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    imgView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
    imgView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
    imgView.heightAnchor.constraint(equalToConstant: 125).isActive = true

    topLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    topLabel.topAnchor.constraint(equalTo: imgView.bottomAnchor, constant: 60).isActive = true
    topLabel.widthAnchor.constraint(equalTo: view.widthAnchor, constant: -50).isActive = true
    topLabel.heightAnchor.constraint(equalToConstant: 50).isActive = true
    topLabel.adjustsFontSizeToFitWidth = true

    inputBox.topAnchor.constraint(equalTo: topLabel.bottomAnchor, constant: 30).isActive = true
    inputBox.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    inputBox.heightAnchor.constraint(equalToConstant: 50).isActive = true
    inputBox.widthAnchor.constraint(equalToConstant: 250).isActive = true

    btn.topAnchor.constraint(equalTo: inputBox.bottomAnchor, constant: 40).isActive = true
    btn.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true

    let navBarImageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 10, height: 10))
    navBarImageView.contentMode = .scaleAspectFit
    let navBarImage = UIImage(named: "bzaLogo")
    navBarImageView.image = navBarImage
    self.navigationController?.navigationItem.titleView = navBarImageView
}

And where I set the image back on the imageView:

func didSelect(image: UIImage?) {
    self.imgView.image = image
    self.global.uploadFile(imageView: self.uploadIcon.imageView!)
}

And where I add the subviews:

override func viewDidLoad() {
    super.viewDidLoad()
    currentState = 0
    imgView.translatesAutoresizingMaskIntoConstraints = false
    topLabel.translatesAutoresizingMaskIntoConstraints = false
    inputBox.translatesAutoresizingMaskIntoConstraints = false
    btn.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(imgView)
    view.addSubview(topLabel)
    view.addSubview(inputBox)
    view.addSubview(btn)

    inputBox.addTarget(self, action: #selector(inputBoxClicked(textField:)), for: .touchDown)
    imagePicker = ImagePicker(presentationController: self, delegate: self)
    viewModel.state = currentState
    inputBox.delegate = self

    setupLayout()
}

And here is the error getting thrown:

2019-06-12 13:22:16.635903-0600 bZa[39792:1836482] *** Terminating app due to uncaught exception 'NSGenericException', reason: 'Unable to activate constraint with anchors and because they have no common ancestor. Does the constraint or its anchors reference items in different view hierarchies? That's illegal.'

Answer 1

Currently the problem is that you add constraints between views who has no comment ancestor so verify that you add

view.addSubview(imgView)  
view.addSubview(topLabel) 
view.addSubview(inputBox)
view.addSubview(btn)

Also don't forget

imgView.translatesAutoresizingMaskIntoConstraints = false 
topLabel.translatesAutoresizingMaskIntoConstraints = false
inputBox.translatesAutoresizingMaskIntoConstraints = false
btn.translatesAutoresizingMaskIntoConstraints = false