scnscene is nil every time

Question

Hi there I'm trying to create an AR app on which I have every file ordered in few different catalogues and now when I want to create the scene I can not to catch my Models.scnscene catalogue I was trying to do this in so many ways but on each time I've got the same error which is SCNSCENE is nil.

let scene = SCNScene(named: "cup.scn", inDirectory: "../Resources/Models.scnassets", options: nil)
        let node = scene?.rootNode.childNode(withName: selectedItem, recursively: false)
        let transform = hitResults.worldTransform
        let thirdColumn = transform.columns.3
        node?.position = SCNVector3(thirdColumn.x, thirdColumn.y, thirdColumn.z)

        self.sceneView.scene.rootNode.addChildNode(node!)