How to change height of UIView that already has height anchor?

Question

If I have this for a child view controller:

autoCompleteViewController.view.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.act         


        

Answer 1

You can do something like this:

class ViewController: UIViewController {

    var constantValue: CGFloat = 44

    let childView: UIView = {
        let view = UIView()
        view.backgroundColor = .red
        return view
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(childView)

        childView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            childView.topAnchor.constraint(equalTo: view.topAnchor, constant: 0),
            childView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0),
            childView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 0),
            childView.heightAnchor.constraint(equalToConstant: constantValue)
            ])

    }

    @IBAction func changeHeight(_ sender: UIButton) {

        constantValue = 100

        UIView.animate(withDuration: 0.5, animations: {

            if let constraint = (self.childView.constraints.filter{$0.firstAttribute == .height}.first) {

                constraint.constant = self.constantValue
            }

            self.view.layoutIfNeeded()
        })
    }

}