UIViewController multiple inheritance - ios

Question

I have a class called BaseViewController which contains a function where I can add a header to my VC and anchor it
class BaseViewController: UIViewController {
let headerView: UIView = {
let view = UIView()
view.backgroundColor = UIColor.green
return view
}()
func addHeader() {
view.addSubview(headerView)
// then anchor it to top
}
}
I have another class called ScrollViewController which adds a scrollViewController to my VC and anchors it
class ScrollViewController: UIViewController {
let scrollView: UIScrollView = {
let view = UIScrollView()
view.backgroundColor = UIColor.green
return view
}()
func addScrollView() {
view.addSubview(scrollView)
// then anchor it to top
}
}
Finally my main class HomeViewController wants to have both a header and a scrollView so I inherit from both like this:
class HomeViewController: ScrollViewController, BaseViewController {
override viewDidLoad() {
super.viewDidLoad()
addScrollView()
addHeaderView()
let view = UIView()
//anchor view to bottom of the header
}
}
However swift doesn't allow multiple inheritance so I tried using protocols and extensions which works but the problem is that I want other views to be able to be anchored to the header and scrollView so it didn't fit my needs.
What could I do so I can implement something like that
Thanks

Answer 1

Swift does not support multiple inheritance. However, protocols and protocol extensions can accomplish what you want.
Example:
protocol HeaderProtocol {
func addHeaderView() -> UIView
}
extension HeaderProtocol where Self: UIViewController {
func addHeaderView() -> UIView {
let headerView = UIView()
headerView.backgroundColor = UIColor.green
view.addSubview(headerView)
// then anchor it to top
return headerView
}
}
protocol ScrollViewProtocol {
func addScrollView() -> UIView
}
extension ScrollViewProtocol where Self: UIViewController {
func addScrollView() -> UIView {
let scrollView = UIScrollView()
scrollView.backgroundColor = UIColor.green
view.addSubview(scrollView)
// then anchor it to top
return scrollView
}
}
class HomeViewController: UIViewController, ScrollViewProtocol, HeaderProtocol {
override func viewDidLoad() {
super.viewDidLoad()
let scrollView = addScrollView()
let headerView = addHeaderView()
}
}
Alternative approach:
protocol HeaderProtocol {
var headerView: UIView? { get set }
func addHeaderView() -> UIView
}
extension HeaderProtocol where Self: UIViewController {
func addHeaderView() -> UIView {
let headerView = UIView()
headerView.backgroundColor = UIColor.green
view.addSubview(headerView)
// then anchor it to top
return headerView
}
}
protocol ScrollViewProtocol {
var scrollView: UIView? { get set }
func addScrollView() -> UIView
}
extension ScrollViewProtocol where Self: UIViewController {
func addScrollView() -> UIView {
let scrollView = UIScrollView()
scrollView.backgroundColor = UIColor.green
view.addSubview(scrollView)
// then anchor it to top
return scrollView
}
}
class HomeViewController: UIViewController, ScrollViewProtocol, HeaderProtocol {
var scrollView: UIView?
var headerView: UIView?
override func viewDidLoad() {
super.viewDidLoad()
scrollView = addScrollView()
headerView = addHeaderView()
}
}