UIStackView + UIView test

playground.swift

import UIKit

var a = UIView()
var b = UIView()
var c = UIView()

a.backgroundColor = #colorLiteral(red: 0.1019607857, green: 0.2784313858, blue: 0.400000006, alpha: 1)
b.backgroundColor = #colorLiteral(red: 0.9254902005, green: 0.2352941185, blue: 0.1019607857, alpha: 1)
c.backgroundColor = #colorLiteral(red: 0.4666666687, green: 0.7647058964, blue: 0.2666666806, alpha: 1)

var stackView = UIStackView(frame: CGRect(x: 0, y: 0, width: 500, height: 800))

stackView.axis = .vertical
stackView.distribution = .fill

a.heightAnchor.constraint(equalToConstant: 70).isActive = true

b.heightAnchor.constraint(greaterThanOrEqualToConstant: 0).isActive = true

c.heightAnchor.constraint(equalToConstant: 70).isActive = true

stackView.addArrangedSubview(a)
stackView.addArrangedSubview(b)
stackView.addArrangedSubview(c)