How to create 3D Virtual Content with SceneKit in Swift 4

I am using this to create a simple 3D object in Single View application. In a default configuration, the following code places a 10-centimeter cube 20 centimeters in front of the camera's initial position

let cubeNode = SCNNode(geometry: SCNBox(width: 0.1, height: 0.1, length: 0.1, chamferRadius: 0))
cubeNode.position = SCNVector3(0, 0, -0.2) 
sceneView.scene.rootNode.addChildNode(cubeNode)

When plane detection is enabled, ARKit adds and updates anchors for each detected plane. To add visual content for these anchors, implement ARSCNViewDelegate methods such as the following:

func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
    guard let planeAnchor = anchor as? ARPlaneAnchor else { return }
    let plane = SCNPlane(width: CGFloat(planeAnchor.extent.x), height: CGFloat(planeAnchor.extent.z))
    let planeNode = SCNNode(geometry: plane)
    planeNode.position = SCNVector3Make(planeAnchor.center.x, 0, planeAnchor.center.z)
    planeNode.transform = SCNMatrix4MakeRotation(-Float.pi / 2, 1, 0, 0)
    node.addChildNode(planeNode)
}

How can i rander the 3D Object.