Ease out animation for SKSpriteNode - ios

Question

I'm moving a sprite by using the touchesMoved method. So far this is working fine, but the result looks a little bit unnatural. The sprite stops immediately, once the movement of my finger stops. A more natural impression would be, if the sprite continuous the movement a little time with an ease out function. Any idea how to implement this?
Here is my code:
import SpriteKit
class GameScene: SKScene {
var sprite: SKSpriteNode?
var xOrgPosition: CGFloat = 0.0
override func didMoveToView(view: SKView) {
sprite = SKSpriteNode(imageNamed:"Spaceship")
sprite!.xScale = 0.1
sprite!.yScale = 0.1
sprite!.position = CGPoint(x:CGRectGetMidX(self.frame), y:CGRectGetMidY(self.frame));
self.addChild(sprite!)
}
override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
for touch in touches {
let xTouchPosition = touch.locationInNode(self).x
if xOrgPosition != 0.0 {
// calculate the new position
sprite!.position = CGPoint(x: sprite!.position.x - (xOrgPosition - xTouchPosition), y: sprite!.position.y)
}
// Store the current touch position to calculate the delta in the next iteration
xOrgPosition = xTouchPosition
}
}
override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
// Reset value for the next swipe gesture
xOrgPosition = 0
}
}
Update:
I've made a short sample project, based on the answers from hamobi
Tutorial
Git repository

Answer 1

i think this might be what youre going for. let me know if you have any questions :)
import SpriteKit
class GameScene: SKScene {
var sprite: SKSpriteNode?
var xOrgPosition: CGFloat?
override func didMoveToView(view: SKView) {
sprite = SKSpriteNode(imageNamed:"Spaceship")
sprite!.xScale = 0.1
sprite!.yScale = 0.1
sprite!.position = CGPoint(x:CGRectGetMidX(self.frame), y:CGRectGetMidY(self.frame));
self.addChild(sprite!)
}
override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
for touch in touches {
xOrgPosition = touch.locationInNode(self).x
}
}
override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
xOrgPosition = nil
}
override func update(currentTime: NSTimeInterval) {
if let xPos = xOrgPosition {
sprite!.position.x += (xPos - sprite!.position.x) * 0.1
}
}
}