SceneKit-将DAE加载到SCNNode中（展开错误）

Question

I'm currently trying to import a dae file into a SCNNode that will then be added to a scene. I found some great stuff on here but I've hit a wall.

The answer I've been trying to implement was found here - Stackoverflow: load a collada (dae) file into SCNNode (Swift - SceneKit)

I've tried to implement the top solution but I get an error which says:

"Value of optional type 'SCNNode?' not unwrapped; did you mean to use '!' or '?'

It may be that I've overlooked something very fundamental, I am very much a novice.

I'll include my ViewController viewDidload code below, if anyone could shed some light on this I would be infinitely grateful!

let scnView = self.view as SCNView
let scene = MasterScene()
scnView.scene = scene
scnView.backgroundColor = UIColor.grayColor()

// enable default lighting
scnView.autoenablesDefaultLighting = true
// enable default camera
scnView.allowsCameraControl = true

var node = SCNNode()
let assetScene = SCNScene(named: "s185.dae")
scene.rootNode.addChildNode(assetScene?.rootNode.childNodeWithName("s185", recursively: true))
// Last line produces error

Answer 1

Your assetScene is an optional. You seem to have got that part, since you're using optional chaining to access its rootNode .

However, any result produced by an expression that uses optional chaining is itself an optional — you don't know that assetScene exists, so you don't know if anything you tried to get out of it exists, either.

But addChildNode takes a non-optional SCNNode — you can't pass an optional to it. You need to unwrap that optional first. Even if you unwrap assetScene with an if let , you'll still get an optional, because you don't know if childNodeWithName found a node.

Try something like this:

 if let assetScene = SCNScene(named: "s185.dae") {
      if let node = assetScene.rootNode.childNodeWithName("s185", recursively: true) {
           scene.rootNode.addChildNode(node)
      }
 }