Relative Sizing for views on iOS using UIKit

RelativeView.swift

import Foundation
import UIKit

class RelativeView: UIView {
    
    @IBInspectable var width: CGFloat = 1.0
    @IBInspectable var height: CGFloat = 1.0
    override var intrinsicContentSize: CGSize {
        return CGSize(width: width, height: height)
    }
}

class RelativeStackView: UIStackView {
    
    @IBInspectable var width: CGFloat = 1.0
    @IBInspectable var height: CGFloat = 1.0
    override var intrinsicContentSize: CGSize {
        return CGSize(width: width, height: height)
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        initStach()
    }
    
    required init(coder: NSCoder) {
        super.init(coder: coder)
        initStach()
    }
    
    private func initStach() {
        distribution = .fillProportionally
    }
}

@IBDesignable
class TestView : UIView {
    
    var wrapper = UIStackView()
    var halfView = RelativeView()
    var lowerSection = RelativeStackView()
    var quarterView1 = RelativeView()
    var quarterView2 = RelativeView()
    
    var viewsDict: [String:UIView] = [String:UIView]()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        initUI()
    }
    
    required convenience init?(coder aDecoder: NSCoder) {
        self.init(coder: aDecoder)
        initUI()
    }
    
    func initUI() {
        
        // Setup view hierarchy
        addSubview(wrapper)
        wrapper.addArrangedSubview(halfView)
        wrapper.addArrangedSubview(lowerSection)
        lowerSection.addArrangedSubview(quarterView1)
        lowerSection.addArrangedSubview(quarterView2)
        
        // Configure Wrapper Stackview
        wrapper.distribution = .fillProportionally
        wrapper.axis = .vertical
        
        viewsDict = [
            "wrapper" : wrapper,
            "halfView" : halfView,
            "lowerSection" : lowerSection,
            "quarterView1" : quarterView1,
            "quarterView2" : quarterView2,
        ]
        
        _ = viewsDict.map {
            $0.value.translatesAutoresizingMaskIntoConstraints = false
        }
        
        addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[wrapper]|", options: [], metrics: nil, views: viewsDict))
        addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[wrapper]|", options: [], metrics: nil, views: viewsDict))
     
        
        // Configure Child View Heights
        // NOTE: THIS IS THE BIT THAT ISN'T WORKING!!!!
        halfView.height = 2.0
        halfView.backgroundColor = UIColor.red
        
        lowerSection.height = 1.0
        
        quarterView1.width = 1.0
        quarterView1.backgroundColor = UIColor.yellow
        
        quarterView2.width = 2.0
        quarterView2.backgroundColor = UIColor.blue
    }
}