How to make enemy have independent lives?

Question

PLEASE HELP!!! I have been trying to figure this out for along time. I have searched the internet and i cannot find anything that will help me.

I am currently making a game in which you are a space ship in the middle and enemy ships are moving towards you and you have to shoot them. some enemies have different lives. for example: a red ship takes one shot to explode, the blue ship takes 3, etc. I have everything to work only the lives. for example: whenever a blue ship is called on to the screen i shoot it once so its life goes down to 2. but whenever a another blue ship is called the first blue ship has its life reset back to 3 again. Is there anyway I can make it so that whenever a ship looses lives it remains that way even if other ships are called ?

this is my ship function that gets called and adds enemy space ships onto the screen:

func VillainRight(){
    let TooMuch = self.size.width
    let point = UInt32(TooMuch)
    life = 3
    let VillainR = SKSpriteNode(imageNamed: "BlueVillain")

    VillainR.zPosition = 2
    VillainR.position = CGPoint(x: self.frame.minX,y: CGFloat(arc4random_uniform(point)))

    //This code makes the villain's Zposition point towards the SpaceShip
    let angle = atan2(SpaceShip.position.y - VillainR.position.y, SpaceShip.position.x - VillainR.position.x)
    VillainR.zRotation = angle - CGFloat(M_PI_2)


    let MoveToCenter = SKAction.move(to: CGPoint(x: self.frame.midX, y: self.frame.midY), duration: 15)

    //Physics World
    VillainR.physicsBody = SKPhysicsBody(rectangleOf: VillainR.size)
    VillainR.physicsBody?.categoryBitMask = NumberingPhysics.RightV
    VillainR.physicsBody?.contactTestBitMask = NumberingPhysics.Laser | NumberingPhysics.SpaceShip
    VillainR.physicsBody?.affectedByGravity = false
    VillainR.physicsBody?.isDynamic = true






    VillainR.run(MoveToCenter)
    addChild(VillainR)
    }

This is the code that calls this function:

_ = Timer.scheduledTimer(timeInterval: 5.0, target: self, selector: #selector(Level1.VillainRight), userInfo: nil, repeats: true)

I am using the spritekit in Swift. Thank You Very Much in advance!

Answer 1

That is happening because life variable is declared as a property of a scene and it is not local to a specific node (enemy ship). You can solve this in a few ways... First way would be using node's userData property:

import SpriteKit

let kEnergyKey = "kEnergyKey"

class GameScene: SKScene, SKPhysicsContactDelegate {

    override func didMove(to view: SKView) {


        let blueShip = getShip(energy: 3)
        let greenShip = getShip(energy: 2)
        let redShip = getShip(energy: 1)

        if let blueShipEnergy = blueShip.userData?.value(forKey: kEnergyKey) as? Int {

            print("Blue ship has \(blueShipEnergy) lives left")
            //hit the ship
            blueShip.userData?.setValue(blueShipEnergy-1, forKey: kEnergyKey)

            if let energyAfterBeingHit = blueShip.userData?.value(forKey: kEnergyKey) as? Int {

                print("Blue ship has \(energyAfterBeingHit) lives left")
            }
        }
    }

    func getShip(energy:Int)->SKSpriteNode{
        //determine which texture to load here based on energy value
        let ship = SKSpriteNode(color: .purple, size: CGSize(width: 50, height: 50))

        ship.userData = [kEnergyKey:energy]

        return ship
    }
}

This is what the docs say about userData property:

You use this property to store your own data in a node. For example, you might store game-specific data about each node to use inside your game logic. This can be a useful alternative to creating your own node subclasses to hold game data.

As you can see, an alternative to this is subclassing of a node (SKSpriteNode):

class Enemy:SKSpriteNode {

    private var energy:Int
    //do initialization here
}