如何在ARSCNView上添加SCNNode运行时？

import ARKit

class ViewController: UIViewController, ARSCNViewDelegate {
    @IBOutlet var sceneView: ARSCNView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 设置AR场景的代理
        sceneView.delegate = self
        
        // 创建一个3D模型
        let sphere = SCNSphere(radius: 0.1)
        let material = SCNMaterial()
        material.diffuse.contents = UIColor.red
        sphere.materials = [material]
        let node = SCNNode(geometry: sphere)
        
        // 设置节点的位置
        node.position = SCNVector3(0, 0, -1)
        
        // 将节点添加到AR场景中
        sceneView.scene.rootNode.addChildNode(node)
        
        // 运行ARSession
        let configuration = ARWorldTrackingConfiguration()
        sceneView.session.run(configuration)
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        // 配置ARSession
        let configuration = ARWorldTrackingConfiguration()
        sceneView.session.run(configuration)
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        
        // 暂停ARSession
        sceneView.session.pause()
    }
    
    // ARSCNViewDelegate方法，用于处理AR场景的更新
    func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
        // 处理AR场景的更新逻辑
    }
}