Throwing an object with SpriteKit - ios

Question

I have the following code at the moment. Even though the code build is successful, i cannot seem to get it to work. I am trying to make it so when you flick the object, it moves at the velocity of your begin and end touch.
import SpriteKit
class GameScene: SKScene {
var sprite: SKSpriteNode!
var touchPoint: CGPoint = CGPoint()
var touching: Bool = false
override func didMoveToView(view: SKView) {
self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame)
sprite = SKSpriteNode(color: UIColor.redColor(), size: CGSize(width: 50, height: 50))
sprite.physicsBody = SKPhysicsBody(rectangleOfSize: sprite.size)
sprite.position = CGPoint(x: self.size.width/2.0, y: self.size.height/2.0)
self.addChild(sprite)
}
//for touch: AnyObject in touches {
//let location = touch.locationInNode(self)
//let touchedNode = self.nodeAtPoint(location)
override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
for touch: AnyObject in touches {
let location = touch.locationInNode(self)
if sprite.frame.contains(location) {
touchPoint = location
touching = true
}
}
func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
for touch: AnyObject in touches {
let location = touch.locationInNode(self)
touchPoint = location
}
func touchesEnded(touches: Set<NSObject>, withEvent event: UIEvent) {
touching = false
}
func update(currentTime: CFTimeInterval) {
if touching {
let dt:CGFloat = 1.0/60.0
let distance = CGVector(dx: touchPoint.x-sprite.position.x, dy: touchPoint.y-sprite.position.y)
let velocity = CGVector(dx: distance.dx/dt, dy: distance.dy/dt)
sprite.physicsBody!.velocity = velocity
}
}
}}}

Answer 1

You accidentally placed touchesMoved, touchesEnded and update inside touchesBegan. Besides that your code works. A hint that there were problems was the fact you didn't need to prefix touchesMoved, touchesEnded or update with override.
In the future, I would recommend using breakpoints and print statements to check the methods you expect to execute, are in fact running. Doing that you'd see that your versions of touchesMoved, touchesEnded and update weren't being called.
Anyway, here's it corrected it and now it works perfectly:
import SpriteKit
class GameScene: SKScene {
var sprite: SKSpriteNode!
var touchPoint: CGPoint = CGPoint()
var touching: Bool = false
override func didMoveToView(view: SKView) {
self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame)
sprite = SKSpriteNode(color: UIColor.redColor(), size: CGSize(width: 50, height: 50))
sprite.physicsBody = SKPhysicsBody(rectangleOfSize: sprite.size)
sprite.position = CGPoint(x: self.size.width/2.0, y: self.size.height/2.0)
self.addChild(sprite)
}
override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
for touch: AnyObject in touches {
let location = touch.locationInNode(self)
if sprite.frame.contains(location) {
touchPoint = location
touching = true
}
}
}
override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
for touch: AnyObject in touches {
let location = touch.locationInNode(self)
touchPoint = location
}
}
override func touchesEnded(touches: Set<NSObject>, withEvent event: UIEvent) {
touching = false
}
override func touchesCancelled(touches: Set<NSObject>!, withEvent event: UIEvent!) {
touching = false
}
override func update(currentTime: NSTimeInterval) {
if touching {
let dt:CGFloat = 1.0/60.0
let distance = CGVector(dx: touchPoint.x-sprite.position.x, dy: touchPoint.y-sprite.position.y)
let velocity = CGVector(dx: distance.dx/dt, dy: distance.dy/dt)
sprite.physicsBody!.velocity = velocity
}
}
}

Answer 2

ABakerSmith's solutions updated for Swift 4:
import SpriteKit
class GameScene: SKScene {
var sprite: SKSpriteNode!
var touchPoint: CGPoint = CGPoint()
var touching: Bool = false
override func didMove(to view: SKView) {
self.physicsBody = SKPhysicsBody.init(edgeLoopFrom: self.frame)
sprite = SKSpriteNode(color: .red, size: CGSize(width: 50, height: 50))
sprite.physicsBody = SKPhysicsBody.init(rectangleOf: sprite.size)
sprite.position = CGPoint(x: self.size.width/2.0, y: self.size.height/2.0)
self.addChild(sprite)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
if let touch = touches.first?.location(in: self) {
if sprite.frame.contains(touch) {
touchPoint = touch
touching = true
}
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for t in touches {
let location = t.location(in: self)
touchPoint = location
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
touching = false
}
override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
touching = false
}
override func update(_ currentTime: TimeInterval) {
if touching {
let dt:CGFloat = 1.0/60.0
let distance = CGVector(dx: touchPoint.x-sprite.position.x, dy: touchPoint.y-sprite.position.y)
let velocity = CGVector(dx: distance.dx/dt, dy: distance.dy/dt)
sprite.physicsBody!.velocity = velocity
}
}
}

Answer 3

Solution updated to not have the touch/drag snap to the middle of the sprite. If you're dragging/throwing an object you're going to want that throw to come from where the user touched the object and not snap to the middle of the object. This will make it look a lot smoother
import SpriteKit
class GameScene: SKScene {
var sprite: SKSpriteNode!
var touchPoint: CGPoint = CGPoint()
var touching: Bool = false
var xDif = CGFloat()
var yDif = CGFloat()
override func didMove(to view: SKView) {
self.physicsBody = SKPhysicsBody.init(edgeLoopFrom: self.frame)
sprite = SKSpriteNode(color: .red, size: CGSize(width: 50, height: 50))
sprite.physicsBody = SKPhysicsBody.init(rectangleOf: sprite.size)
sprite.position = CGPoint(x: self.size.width/2.0, y: self.size.height/2.0)
self.addChild(sprite)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
if let touch = touches.first?.location(in: self) {
xDif = sprite.position.x - touch.x
yDif = sprite.position.y - touch.y
if sprite.frame.contains(touch) {
touchPoint = touch
touching = true
}
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for t in touches {
let location = t.location(in: self)
touchPoint = location
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
touching = false
}
override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
touching = false
}
override func update(_ currentTime: TimeInterval) {
if touching {
let dt:CGFloat = 1.0/60.0
let distance = CGVector(dx: touchPoint.x-sprite.position.x + xDif, dy: touchPoint.y-sprite.position.y + yDif)
let velocity = CGVector(dx: distance.dx/dt, dy: distance.dy/dt)
sprite.physicsBody!.velocity = velocity
}
}
}