What algorithm is available to correlate a SKSpriteNode's position with the UIBezierPath's currentPoint?

What algorithm is available to correlate a SKSpriteNode's position with the UIBezierPath's currentPoint?

I have this code (GameViewController) which implements the following of a SKSpriteNode along a UIBezierPath:

func createTrainPath() {    trackRect = CGRect(x: tracksPosX - tracksWidth/2,                       y: tracksPosY,                       width: tracksWidth,                       height: tracksHeight)    trainPath = UIBezierPath(ovalIn: trackRect)}   // createTrainPathfunc startFollowTrainPath() {    var trainAction = SKAction.follow(                                  trainPath.cgPath,                                  asOffset: false,                                  orientToPath: true,                                  speed: theSpeed)    trainAction = SKAction.repeatForever(trainAction)    myTrain.run(trainAction, withKey: runTrainKey)}   // startFollowTrainPathfunc stopFollowTrainPath() {    guard myTrain == nil else {        myTrain.removeAction(forKey: runTrainKey)        savedTrainPosition = getPositionFor(myTrain, orPath: trainPath)        return    }}   // stopFollowTrainPath

The user of this segment can bring up another SKScene .. at which action I call stopFollowTrainPath() and save the position of the SKSpriteNode to the global savedTrainPosition via:

func getPositionFor(_ node: SKSpriteNode, orPath: UIBezierPath) -> CGPoint {    if (useNode) {        return node.position    }    else {        return orPath.currentPoint    }}   // getPositionFor

(1) When the user returns from looking at the other SKScene, I want the moving (following) SKSpriteNode to continue moving around the UIBezierPath starting where I stopped the Node before presenting the other SKScene.

(2) If the SKSpriteNode is not moving before the other SKScene is brought up, I need the position of the SKSpriteNode to remain where it was before the new SKScene was presented.

What is the best method for doing these?