Simple UIView example for Lessons in SwiftUI blog post

simple-uikit-view.swift

import UIKit

class SimpleUIKitView: UIView {
    
    lazy var button: ButtonPrimary = {
        let button = ButtonPrimary() // internal button class
        button.title = "Primary Button"
        button.translatesAutoresizingMaskIntoConstraints = false
        return button
    }()
    
    lazy var heading: LabelHeadingBase = {
        let label = LabelHeadingBase() // internal label class
        label.text = "Heading Base"
        label.textAlignment = .center
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()
    
    lazy var stackView: UIStackView = {
        let view = UIStackView()
        view.axis = .vertical
        view.spacing = 8
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    
    init() {
        super.init(frame: .zero)
        setupView()
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    private func setupView() {
        stackView.addArrangedSubview(heading)
        stackView.addArrangedSubview(button)
        addSubview(stackView)
        
        NSLayoutConstraint.activate([
            stackView.centerXAnchor.constraint(equalTo: centerXAnchor),
            stackView.centerYAnchor.constraint(equalTo: centerYAnchor)
        ])
    }
}