Roubar forneceuuma ótima solução Objective-C para subclassificar NSOperation para obter um mecanismo de enfileiramento serial para objetos SKAction. Eu implementei isso com sucesso em meu próprio projeto Swift.

import SpriteKit

class ActionOperation : NSOperation
{
    let _node: SKNode // The sprite node on which an action is to be performed
    let _action: SKAction // The action to perform on the sprite node
    var _finished = false // Our read-write mirror of the super's read-only finished property
    var _executing = false // Our read-write mirror of the super's read-only executing property

    /// Override read-only superclass property as read-write.
    override var executing: Bool {
        get { return _executing }
        set {
            willChangeValueForKey("isExecuting")
            _executing = newValue
            didChangeValueForKey("isExecuting")
        }
    }

    /// Override read-only superclass property as read-write.
    override var finished: Bool {
        get { return _finished }
        set {
            willChangeValueForKey("isFinished")
            _finished = newValue
            didChangeValueForKey("isFinished")
        }
    }

    /// Save off node and associated action for when it's time to run the action via start().
    init(node: SKNode, action: SKAction) {

    // This is equiv to ObjC:
    // - (instancetype)initWithNode(SKNode *)node (SKAction *)action
    // See "Exposing Swift Interfaces in Objective-C" at https://developer.apple.com/library/mac/documentation/Swift/Conceptual/BuildingCocoaApps/InteractingWithObjective-CAPIs.html#//apple_ref/doc/uid/TP40014216-CH4-XID_35

        _node = node
        _action = action
        super.init()
    }

    /// Add the node action to the main operation queue.
    override func start()
    {
        if cancelled {
            finished = true
            return
        }

        executing = true

        NSOperationQueue.mainQueue().addOperationWithBlock {
            self._node.runAction(self._action) {
                self.executing = false
                self.finished = true
            }
        }
    }
}

Para usar o ActionOperation, instancie um membro da classe NSOperationQueue na sua classe cliente:

var operationQueue = NSOperationQueue()

Adicione esta linha importante ao seu método init:

operationQueue.maxConcurrentOperationCount = 1; // disallow follow actions from overlapping one another

E então, quando você estiver pronto para adicionar SKActions a ele, eles serão executados em série:

operationQueue.addOperation(ActionOperation(node: mySKNode, action: mySKAction))

Se você precisar finalizar as ações a qualquer momento:

operationQueue.cancelAllOperations() // this renders the queue unusable; you will need to recreate it if needing to queue anymore actions

Espero que ajude!