Alternative to animation(forKey:) (now deprecated)?

Question

I am working with iOS 11 (for ARKit) and while many point to a sample app for SceneKit from Apple with a Fox, I am having problem with the extension it uses in that sample project (file) to add animations:

extension CAAnimation {
    class func animationWithSceneNamed(_ name: String) -> CAAnimation? {
        var animation: CAAnimation?
        if let scene = SCNScene(named: name) {
            scene.rootNode.enumerateChildNodes({ (child, stop) in
                if child.animationKeys.count > 0 {
                    animation = child.animation(forKey: child.animationKeys.first!)
                    stop.initialize(to: true)
                }
            })
        }
        return animation
    }
}

It seems that this extension is very handy but I am not sure how to migrate this now that it is deprecated? Is it built into SceneKit by default now?

The documentation didn't really show much info on why it was deprecated or where to go from here.

Thanks

Answer 1

Lësha Turkowski's answer without force unwraps.

extension SCNAnimationPlayer {

    class func loadAnimationPlayer(from sceneName: String) -> SCNAnimationPlayer? {
        var animationPlayer: SCNAnimationPlayer?

        if let scene = SCNScene(named: sceneName) {
            scene.rootNode.enumerateChildNodes { (child, stop) in
                if !child.animationKeys.isEmpty {
                    animationPlayer = child.animationPlayer(forKey: child.animationKeys[0])
                    stop.pointee = true
                }
            }
        }

        return animationPlayer
    }
}

Answer 2

TL;DR: examples of how to use new APIs can be found in Apple's sample game (search for SCNAnimationPlayer)

---

Even though animation(forKey:) and its sister methods that work with CAAnimation have been deprecated in iOS11, you can continue using them – everything will work.

But if you want to use new APIs and don't care about backwards compatibility (which you wouldn't need in the case of ARKit anyway, because it's only available since iOS11), read on.

The newly introduced SCNAnimationPlayer provides a more convenient API compared to its predecessors. It is now easier to work with animations in real time. This video from WWDC2017 would be a good starting point to learn about it.

As a quick summary: SCNAnimationPlayer allows you to change animation's speed on the fly. It provides a more intuitive interface for animation playback using methods such as play() and stop() compared to adding and removing CAAnimations. You also can blend two animations together which, for example, can be used to make smooth transitions between them.

You can find examples of how to use all of this in the Fox 2 game by Apple.

---

Here's the extension you've posted adapted to use SCNAnimationPlayer (which you can find in the Character class in the Fox 2 sample project):

extension SCNAnimationPlayer {
    class func loadAnimation(fromSceneNamed sceneName: String) -> SCNAnimationPlayer {
        let scene = SCNScene( named: sceneName )!
        // find top level animation
        var animationPlayer: SCNAnimationPlayer! = nil
        scene.rootNode.enumerateChildNodes { (child, stop) in
            if !child.animationKeys.isEmpty {
                animationPlayer = child.animationPlayer(forKey: child.animationKeys[0])
                stop.pointee = true
            }
        }
        return animationPlayer
    }
}

You can use it as follows:

1. Load the animation and add it to the corresponding node

   let jumpAnimation = SCNAnimationPlayer.loadAnimation(fromSceneNamed: "jump.scn")
   jumpAnimation.stop() // stop it for now so that we can use it later when it's appropriate 
   model.addAnimationPlayer(jumpAnimation, forKey: "jump")
   

2. Use it!

   model.animationPlayer(forKey: "jump")?.play()