SimpleStackView

class SimpleStackView: UIView {

	var padding:CGFloat = 0 {
		didSet {
			setNeedsLayout()
		}
	}
	
	var spacing:CGFloat = 0 {
		didSet {
			setNeedsLayout()
		}
	}
	
	var arrangedSubViews:[UIView]? {
		willSet {
			guard let arrangedSubViews = arrangedSubViews else { return }
			
			for arrangedSubView in arrangedSubViews {
				if arrangedSubView.isDescendant(of: self) {
					arrangedSubView.removeFromSuperview()
				}
			}
		}
		didSet {
			guard let arrangedSubViews = arrangedSubViews else { return }
			
			for arrangedSubView in arrangedSubViews {
				addSubview(arrangedSubView)
			}
			
			setNeedsLayout()
		}
	}
	
	override func sizeThatFits(_ size: CGSize) -> CGSize {
		guard let arrangedSubViews = arrangedSubViews, arrangedSubViews.count > 0 else { return CGSize.zero }
		
		var heightThatFits:CGFloat = 0
		
		let contentSize = CGSize.init(width: size.width-2*padding, height: size.height-2*padding)
		
		for arrangedSubView in arrangedSubViews {
			heightThatFits += arrangedSubView.sizeThatFits(contentSize).height
		}
		
		heightThatFits += CGFloat(arrangedSubViews.count - 1) * spacing
		
		return CGSize.init(width: size.width, height: heightThatFits + 2*padding)
	}
	
	override func layoutSubviews() {
		super.layoutSubviews()
		
		guard let arrangedSubViews = arrangedSubViews else { return }
		
		let size = self.bounds.size
		let contentSize = CGSize.init(width: size.width-2*padding, height: size.height-2*padding)
		
		var top = padding
		for arrangedSubView in arrangedSubViews {
			let height = arrangedSubView.sizeThatFits(contentSize).height
			arrangedSubView.frame = CGRect.init(x: padding, y: top, width: contentSize.width, height: height)
			top = arrangedSubView.frame.maxY + spacing
		}
	}
	
}