How should I update the curve correctly with touchesMoved function?

Question

I want to make a curve like, when user moved their finger, the curve changed its radian, but the code I did was seems something wrong, with many curve when I moved my finger:( Here was my code below, and followed the terrible build's screenshot. Actually I also want to how to implement this function with UIPanGestureRecognizer.

import SpriteKit
import AVFoundation
import UIKit

class Home: SKScene {

    var happiness:CGFloat {
        return currentPoint.y
    }

    var currentPoint = CGPoint(x: 0, y: 1024)

    override func didMoveToView(view: SKView) {
        backgroundColor = UIColor.blueColor()
    }

    func drawhappiness() {
        let pathNew2 = CGPathCreateMutable()
        let startx:CGFloat = 268
        let starty:CGFloat = 1024
        let cp1x:CGFloat = 568
        let cp1y:CGFloat = happiness
        let cp2x:CGFloat = 968
        let cp2y:CGFloat = happiness
        let endx:CGFloat = 1292
        let endy:CGFloat = 1024
        CGPathMoveToPoint(pathNew2, nil, startx, starty)
        CGPathAddCurveToPoint(pathNew2, nil, cp1x, cp1y, cp2x, cp2y, endx, endy)
        let shapeNew2 = SKShapeNode()
        shapeNew2.path = pathNew2
        shapeNew2.strokeColor = UIColor.greenColor()
        shapeNew2.lineWidth = 10
        addChild(shapeNew2)
    }

    override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
        for touch:AnyObject in touches {
            currentPoint = touch.locationInNode(self)
        }
    }

    override func update(currentTime: NSTimeInterval) {
        drawhappiness()
    }
}

Answer 1

You are adding a new shape node to the scene each time you move your finger. To fix this, create a single shape with global scope in Home , configure the shape in didMoveToView (ie, set line width, color), and update the shape's path property in drawhappiness .

For example,

class Home: SKScene {

    let shapeNew2 = SKShapeNode()
    var currentPoint = CGPoint(x: 0, y: 1024)

    var happiness:CGFloat {
        return currentPoint.y
    }

    override func didMoveToView(view: SKView) {
        backgroundColor = UIColor.blueColor()
        shapeNew2.strokeColor = UIColor.greenColor()
        shapeNew2.lineWidth = 10
        addChild(shapeNew2)
    }

    func drawhappiness() {
        let pathNew2 = CGPathCreateMutable()
        let startx:CGFloat = 268
        let starty:CGFloat = 1024
        let cp1x:CGFloat = 568
        let cp1y:CGFloat = happiness
        let cp2x:CGFloat = 968
        let cp2y:CGFloat = happiness
        let endx:CGFloat = 1292
        let endy:CGFloat = 1024
        CGPathMoveToPoint(pathNew2, nil, startx, starty)
        CGPathAddCurveToPoint(pathNew2, nil, cp1x, cp1y, cp2x, cp2y, endx, endy)
        shapeNew2.path = pathNew2
    }

    override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
        for touch:AnyObject in touches {
            currentPoint = touch.locationInNode(self)
        }
    }

    override func update(currentTime: NSTimeInterval) {
        drawhappiness()
    }
}