Extending iOS `ARSessionDelegate` and getting results from function

I'm trying to extend ARSessionDelegate:

private var arKitSessionDelegate = ARKitSessionDelegate()
arKitView.session.delegate = arKitSessionDelegate

...

class ARKitSessionDelegate: NSObject, ARSessionDelegate {
  func session(_ session: ARSession, didUpdate frame: ARFrame) {
    //do stuff here
  }

   
}

What I don't currently understand is; what's the way to pass the results from the delegate’s functions back to the class that that registers with that delegate?