Moving SpriteKit Node with Touch Gestures only moves one point with each new touch

I have a SpriteKitNode that I want to move around my scene when I touch it and drag it.

I have a touchesBegan method that detects if the particular node I want to move is being touched:

var selectionBoxIsTouched: Bool!
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        for touch in touches{
            let location = touch.location(in: self.canvasScene)
            canvasScene.enumerateChildNodes(withName: "Selection_Box", using:
                                                { [self] (node, stop) -> Void in
                if self.canvasScene.atPoint(location) == node {
                    selectionBoxIsTouched = true
                } else {
                    selectionBoxIsTouched = false
                }
            })
        }
    } 

Next, I have touchesMoved method where if my node is currently being touched, it gets moved as the user moves a finger across the screen:

  
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        if selectionBoxIsTouched {
            if let touch = touches.first {
                let touchLoc = touch.location(in: self.canvasScene)
                let prevTouchLoc = touch.previousLocation(in: self.canvasScene)
                
                canvasScene.enumerateChildNodes(withName: "Selection_Box", using:
                                                    { (node, stop) -> Void in
                    if let touchedNode = node as? SKShapeNode {
                        let newYPos = touchedNode.position.y + (touchLoc.y - prevTouchLoc.y)
                        let newXPos = touchedNode.position.x + (touchLoc.x - prevTouchLoc.x)
                        touchedNode.position = CGPoint(x: newXPos, y: newYPos)  //set new X and Y for your sprite.
                    }
                })
            }
        }
    }

When I select the node + try to move it, it doesn't move in a continuous motion....it moves a small amount, then stops; even if my finger keeps moving across the screen.

How do I fix this so that the node moves in a smooth, continuous motion with my finger?

this touch code should work for you

extension GameScene {

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        for touch in touches{
            let location = touch.location(in: self)
            let _ = self.nodes(at: location).map { ($0 as? DraggableNode)?.isPicked = true }
        }
    }
    
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        for touch in touches{
            let touchLoc = touch.location(in: self)
            let prevTouchLoc = touch.previousLocation(in: self)
            let picked_nodes = self.children.filter { ($0 as? DraggableNode)?.isPicked ?? false }
            for node in picked_nodes {
                let deltaX = touchLoc.x - prevTouchLoc.x
                let deltaY = touchLoc.y - prevTouchLoc.y
                node.position.x += deltaX
                node.position.y += deltaY
            }
        }
    }
    
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        let _ = self.children.map { ($0 as? DraggableNode)?.isPicked = false }
    }
}

combined with the following SKScene. i would recommend putting your picker flag inside the movable node, that way you can drag individual nodes rather than having a single global test.

class DraggableNode: SKNode {
    var isPicked:Bool = false
    override init() {
        super.init()
        let shape = SKShapeNode(circleOfRadius: 50)
        shape.fillColor = .red
        shape.name = "Selection_Box"
        self.addChild(shape)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

class GameScene: SKScene {
    let draggableNodeA = DraggableNode()
    let draggableNodeB = DraggableNode()

    override func didMove(to view: SKView) {
        draggableNodeA.position.x = 50
        draggableNodeB.position.x = -50
        self.addChild(draggableNodeA)
        self.addChild(draggableNodeB)
    }
}