Rotate SKSpritenode by a changing number of degrees - sprite-kit

Question

How can I define an SKAction, and then update the number of degrees my node will rotate? I am trying to define it with variables, but when I update the variable values the action doesn't update.
var degreesToRotate = 4
var direction = 1
let action = SKAction.rotate(byAngle: CGFloat(degreesToRotate * direction), duration: TimeInterval(2))
charector.run(SKAction.repeatForever(action))
direction = -1

Answer 1

import SpriteKit
import GameplayKit
//Extensions borrowed from here : http://stackoverflow.com/a/29179878/3402095
extension Int {
var degreesToRadians: Double { return Double(self) * .pi / 180 }
var radiansToDegrees: Double { return Double(self) * 180 / .pi }
}
extension FloatingPoint {
var degreesToRadians: Self { return self * .pi / 180 }
var radiansToDegrees: Self { return self * 180 / .pi }
}
let kActionKey = "rotate"
class GameScene:SKScene {
let purpleCube = SKSpriteNode(color: .purple, size: CGSize(width: 150, height: 150))
let yellowCube = SKSpriteNode(color: .yellow, size: CGSize(width: 150, height: 150))
override func didMove(to view: SKView) {
addChild(purpleCube)
purpleCube.position.y = purpleCube.size.height
purpleCube.name = "purple"
addChild(yellowCube)
yellowCube.position.y = -yellowCube.size.height
yellowCube.name = "yellow"
let rotate = SKAction.rotate(byAngle: CGFloat(-M_PI * 2.0), duration: 5)
let loop = SKAction.repeatForever(rotate)
purpleCube.run(loop, withKey: kActionKey)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
super.touchesBegan(touches, with: event)
if let touch = touches.first {
let location = touch.location(in: self)
if let cube = atPoint(location) as? SKSpriteNode {
if let name = cube.name {
switch name {
case "purple":
if let action = purpleCube.action(forKey: kActionKey){
purpleCube.run(action.reversed(), withKey: kActionKey)
}
case "yellow":
if action(forKey: "rotating") == nil{
yellowCube.run(SKAction.rotate(byAngle: CGFloat(4.degreesToRadians), duration: 0.1), withKey: kActionKey)
}
default:
break
}
}
}
}
}
}
In this example, there are two nodes that have been rotated in a two different ways. Purple node is rotated constantly at certain speed in clockwise direction. To achieve this, I've created an action that rotates a sprite by 360 degrees... That would be one revolution, which will be repeated forever, thus the sprite will be rotated forever.
About the yellow node...It will be rotated by 4 degrees every time you tap on it. Currently you have to wait that sprite stop rotating so you can rotate it more. This is optional of course, I just wanted to show you the usefulness of action keys.
Rotation Direction
Since in SpriteKit 0 degrees specifies positive x-axis and a positive angle is in counterclockwise direction, I rotated purple cube by -360 degrees, which rotates the sprite in clockwise direction. To find out more about SpriteKit coordinate system, read this documentation section.
Radians Vs Degrees
As you can see, I am talking in degrees, rather than in radians... That is because it would be really hard to say, I rotated the sprite by 6.2831853072 radians :) That is why I used extensions which does conversion from degrees to radians and vice-versa. You might use this often so I added them for you.