This is an extension on UIViews that make it possible to add subviews in a more declarative/hierarchical way.

UIView+Subviews.swift

import UIKit

public extension UIView {

    @discardableResult
    func subviews(@SubviewsBuilder _ subviews: () -> [UIView]) -> UIView {
        subviews().forEach { self.customAddSubview($0) }
        return self
    }

    private func customAddSubview(_ view: UIView) {
        if let stack = self as? UIStackView {
            stack.addArrangedSubview(view)
        } else {
            self.addSubview(view)
        }
    }
}

@_functionBuilder
public struct SubviewsBuilder {
    public static func buildBlock(_ children: UIView...) -> [UIView] {
        return children
    }
}