let sb = UIStoryboard.init(name: "Main", bundle: nil)
var vc10 = sb.instantiateViewController(withIdentifier: "ViewController10")

//vc10.delegate = self // there is the error: Value of type 'UIViewController' hs no member 'delegate'
(ViewController10(vc10)).delegate = self // this did not work too

self.navigationController!.pushViewController(vc10, animated: true)

var delegate:ViewController9?  // this is the property delegate

var vc10 = sb.instantiateViewController(withIdentifier: "ViewController10") as! ViewController10`