Changing a delegate's property through protocol - ios

Question

I have controllingView, that needs to change a property in presentingView. They are both in the same ViewController.
I can let them communicate by making presentingView delegate of controllingView. But it would be far more elegant and flexible, if I could just change the property directly (since
I need to change the presentingView's property's property actually)
I have seen it done in this question: Accessing protocol property in Swift class.
But in controllingView, calling delegate.propertyINeedToChange is nil.
How do I change a delegate's property from the delegating object?
Here is the code:
class MainViewController : UIViewController {
var controllingView = ControllingView()
let presentingView = PresentingView()
override func loadView() {
let view = UIView()
view.backgroundColor = .white
view.addSubview(controllingView)
view.addSubview(presentingView)
self.view = view
controllingView.delegate = presentingView
}
}
class ControllingView: UIView {
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override init(frame: CGRect) {
super.init(frame: frame)
//ControlsView Setup
self.backgroundColor = UIColor(displayP3Red: 0.9, green: 0.9, blue: 0.9, alpha: 1.0)
setupViews()
}
let testSLDR = UISlider()
var delegate: ControlsViewDelegate?
func setupViews() {
self.addSubview(testSLDR)
testSLDR.addTarget(self, action: #selector(testSLDRchanged), for: .valueChanged)
}
#objc func testSLDRchanged() {
delegate?.button?.backgroundColor = UIColor.red
}
}
class PresentingView: UIView, ControlsViewDelegate {
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override init(frame: CGRect) {
super.init(frame: frame)
let button = Button()
self.addSubview(button)
}
var button: Button?
}
protocol ControlsViewDelegate {
var button: Button? { get set }
}
class Button: UIButton { ... }

Answer 1

As the views are initialized in the same view controller you don't need protocol / delegate
Delete the protocol and the associated code
In ControllingView declare a weak Button property
weak var presentingButton : Button?
Replace the line to set the delegate with a line to assign the button of PresentingView to the presentingButton property
controllingView.delegate = presentingView
controllingView.presentingButton = presentingView.button
In the action change the color
#objc func testSLDRchanged() {
presentingButton?.backgroundColor = UIColor.red
}