How to apply multiplier to a var bottom constraint - swift

Question

My code below produces the image below.
What I want is the height of the UIView to be exactly half of the view controller user something like:
constraint(equalTo: view.layoutMarginsGuide.bottomAnchor, multiplier: 1/2)
I dont know where to put it since I am creating a var for every side.
import UIKit
class ViewController: UIViewController {
var myView = UIView()
var topConstraint: NSLayoutConstraint!
var bottomConstraint: NSLayoutConstraint!
var leadingConstraint: NSLayoutConstraint!
var trailingConstraint: NSLayoutConstraint!
var jessicaAlba:Float = 50
override func viewDidLoad() {
super.viewDidLoad()
myView.translatesAutoresizingMaskIntoConstraints = false
myView.backgroundColor = UIColor.orange
view.addSubview(myView)
topConstraint = myView.topAnchor.constraint(equalTo: view.topAnchor, constant: CGFloat(jessicaAlba))
topConstraint.isActive = true
bottomConstraint = myView.bottomAnchor.constraint(equalTo: view.bottomAnchor , constant: CGFloat(-jessicaAlba))
bottomConstraint.isActive = true
leadingConstraint = myView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: CGFloat(jessicaAlba))
leadingConstraint.isActive = true
trailingConstraint = myView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: CGFloat(-jessicaAlba))
trailingConstraint.isActive = true
}
}

Answer 1

You should use heightConstraint instead of bottomConstraint to get that done. Try the snippet below.
import UIKit
class ViewController: UIViewController, UITextFieldDelegate {
var myView = UIView()
var topConstraint: NSLayoutConstraint!
var heightConstraint: NSLayoutConstraint!
var leadingConstraint: NSLayoutConstraint!
var trailingConstraint: NSLayoutConstraint!
var jessicaAlba:Float = 50
override func viewDidLoad() {
super.viewDidLoad()
myView.translatesAutoresizingMaskIntoConstraints = false
myView.backgroundColor = UIColor.orange
view.addSubview(myView)
topConstraint = myView.topAnchor.constraint(equalTo: view.topAnchor, constant: CGFloat(jessicaAlba))
topConstraint.isActive = true
heightConstraint = myView.heightAnchor.constraint(equalTo: view.heightAnchor , multiplier: 0.5, constant: CGFloat(-jessicaAlba))
heightConstraint.isActive = true
leadingConstraint = myView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: CGFloat(jessicaAlba))
leadingConstraint.isActive = true
trailingConstraint = myView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: CGFloat(-jessicaAlba))
trailingConstraint.isActive = true
}
}