Changing texture for subclass of SKSpriteNode? - swift

Question

The update function in the class below, which is a subclass of SKSpriteNode, is supposed to change the texture of the class. According to this SO answer, updating the texture property is sufficient for changing a SKSpriteNode's texture. However, this code doesn't work.
Any ideas why?
class CharacterNode: SKSpriteNode {
let spriteSize = CGSize(width: 70, height: 100)
var level = 0
init(level: Int) {
self.level = level
super.init(texture: nil, color: UIColor.clear, size: spriteSize)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func update(level: Int) {
self.level = level
self.texture = textureForLevel(level: level)
}
func textureForLevel(level: Int) -> SKTexture {
return SKTexture(imageNamed: "TestTexture")
}

Answer 1

Your code works well. In fact this SO answer is correct.
About SKSpriteNode subclass, the update method is a new custom function added by you, because the instance method update(_:) is valid only for SKScene class, this just to say that this function is not performed if it is not called explicitly.
To make a test about your class you can change your code as below( I've changed only textureForLevel method only to make this example):
class CharacterNode: SKSpriteNode {
let spriteSize = CGSize(width: 70, height: 100)
var level = 0
init(level: Int) {
self.level = level
super.init(texture: nil, color: UIColor.clear, size: spriteSize)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func update(level: Int) {
self.level = level
self.texture = textureForLevel(level: level)
}
func textureForLevel(level: Int) -> SKTexture {
if level == 3 {
return SKTexture(imageNamed: "TestTexture3.jpg")
}
return SKTexture(imageNamed: "TestTexture.jpg")
}
}
class GameScene: SKScene {
override func didMove(to view: SKView) {
let characterNode = CharacterNode(level:2)
characterNode.update(level:2)
addChild(characterNode)
characterNode.position = CGPoint(x:self.frame.midX,y:self.frame.midY)
characterNode.run(SKAction.wait(forDuration: 2.0), completion: {
characterNode.update(level:3)
})
}
}
As you can see when you launch GameScene a characterNode sprite will be shown in the center of the screen. After 2 seconds, the texture will change.