How to programmatically increase the height of UIView with Swift

You need to create an outlet for the height constraint of the detail view, and then you can adjust the height programmatically like this myHeightConstraint.constant += extraHeight where extraHeight is a number indicating how much taller you want the detail view to be. You also may need to call self.view.layoutIfNeeded() afterwards.

To create an outlet from a constraint, control drag from the constraint in the storyboard editor (just like you would for an outlet of a UIView) into your code.

You are right - because you are using auto layout and constraints, the adjustments need to be made with constraints too. Setting the raw frames can lead to unexpected behavior. Let me know if you have any other questions or difficulties.

Inside the CGRect initializer you should not be using +=, just +.

Change:

self.view.frame = CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height += 20.0)

to:

self.view.frame = CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height + 20.0)

You should not be trying to change the value of self.view.frame.height inside the initializer.

For me, a programmatic solution wouldn't require me to create an outlet for every height constraint I might want to modify. Here's a code-only solution that works nicely for me. It should work whether the original constraint was created on the storyboard or programmatically. It also provides an option to animate the change if desired -- although I'm not sure if this would work if the view is nested in a complex hierarchy.

extension UIView {
    func setHeight(_ h:CGFloat, animateTime:TimeInterval?=nil) {

        if let c = self.constraints.first(where: { $0.firstAttribute == .height && $0.relation == .equal }) {
            c.constant = CGFloat(h)

            if let animateTime = animateTime {
                UIView.animate(withDuration: animateTime, animations:{
                    self.superview?.layoutIfNeeded()
                })
            }
            else {
                self.superview?.layoutIfNeeded()
            }
        }
    }
}

Swift 4.2

I create an example for you programmatically:

    var flowHeightConstraint: NSLayoutConstraint?

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white

        view.addSubview(button)
        button.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        button.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
        button.widthAnchor.constraint(equalToConstant: 100).isActive = true
        flowHeightConstraint = button.heightAnchor.constraint(equalToConstant: 30)
        flowHeightConstraint?.isActive = true
    }

    @objc func animateButtonTapped() {
        UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.5, initialSpringVelocity: 0.5, options: .curveEaseOut, animations: {
            self.flowHeightConstraint?.constant = 100
            self.view.layoutIfNeeded()
        }, completion: nil)
    }

    lazy var button: UIButton = {
       let button = UIButton()
        button.translatesAutoresizingMaskIntoConstraints = false
        button.backgroundColor = .green
        button.addTarget(self, action: #selector(animateButtonTapped), for: .touchUpInside)
        return button
    }()

this line of code create a button an on tapped change height of button with animation.

hope this help :)