Multiple serial animations in SceneKit

Question

I want to be able to run multiple animations, one after another, in SceneKit. I've implemented a function which runs one animation like so:

fileprivate func animateMove(_ move: Move) {
    print("Animate move started " + move.identifier)

    // I am creating rotateNode
    let rotateNode = SCNNode()
    rotateNode.eulerAngles.x = CGFloat.pi
    scene.rootNode.addChildNode(rotateNode)

    // Then I am selecting nodes which I want to rotate
    nodesToRotate = ...

    // Then I am adding the nodes to rotate node
    _ = nodesToRotate.map { rotateNode.addChildNode($0) }

    SCNTransaction.begin()
    SCNTransaction.animationDuration = move.animationDuration

    SCNTransaction.completionBlock = {
        rotateNode.enumerateChildNodes { node, _ in
            node.transform = node.worldTransform
            node.removeFromParentNode()
            scene.rootNode.addChildNode(node)
        }
        rotateNode.removeFromParentNode()
        print("Animate move finished " + move.identifier)
    }
    SCNTransaction.commit()
}

And then I've tried to run multiple serial animations like so:

    func animateMoves(_ moves: [Move]) {
        for (index, move) in moves.enumerated() {
            perform(#selector(animateMove(_:)), 
            with: move, 
            afterDelay: TimeInterval(Double(index) * move.duration)
        }
    }

Everything is animating but the animations don't run in a serial manner. Animations start and finish in unpredictable time. Sample logs from debugger:

Animate move started 1
Animate move started 2
Animate move finished 1
Animate move finished 2
Animate move started 3
Animate move finished 3

I realise that my approach isn't the best, but only in that way I was able to achieve almost working animations.

I know that there is a SCNAction class available. Maybe I should make many actions within one transaction? If so, could someone explain to me how exactly SCNTransactions work and why the completion SCNTransaction's completion block fires in unpredictable time?

Answer 1

Try to use SCNAction.sequence():

class func sequence([SCNAction])

Creates an action that runs a collection of actions sequentially

let sequence = SCNAction.sequence([action1, action2, action3]) // will be executed one by one

let node = SCNNode()
node.runAction(sequence, completionHandler:nil)