replacing CALayer and CABasicAnimation with SKScene and SKActions

Question

I am trying to restructure this Github Swift project on Metaballs so that the circles are represented by SKShapeNodes that are moved around by SKActions instead of CAB

Answer 1

Assuming that your question is how to replicate the same behaviour with nodes and SKAction, I believe this should do it.

var shapeNode : SKNode?

func startAnimation(){

    if let node = self.shapeNode {
        //assume that we have a node initialized at some point and added to the scene at some x1,y1 coordinates

        /// we define parameters for the animation
        let positionToReach = CGPoint(x: 100, y: 100) /// some random position
        let currentPosition = node.position /// we need the current position to be able to reverse the "animation"
        let animationDuration = 2.5 //loadingAnimation!.duration = 2.5

        /// we define which actions will be run for the node
        let actionForward = SKAction.moveTo(positionToReach, duration: animationDuration)
        let actionBackwards = SKAction.moveTo(currentPosition, duration: animationDuration)

        // we needed two actions to simulate loadingAnimation!.autoreverses = true

        /// we wrap the actions in a sequence of actions
        let actionSequence = SKAction.sequence([actionForward, actionBackwards]) /// animations to repeat

        /// we want to repeat the animation forever
        let actionToRepeat = SKAction.repeatActionForever(actionSequence) ///loadingAnimation!.repeatCount = Float.infinity

        /// showtime
        node.runAction(actionToRepeat)

    }

}

Let me know if I need to update any part as I haven't tested it. You still need to use your actual values and objects.

I have referred to referred to How would I repeat an action forever in Swift? while making this reply.