Swift programming. Possible problem with SKPhysicscontact - swift

Question

I'm working on a project / game and I'm stuck at adding new enemies to the game and to program them. This is how my code looked before I started changing and only had one type of "alien". I want to create two new types, one that you lose 5 points from hitting and one 10. In the code now, there is only one of three and it gives +5 points. How would you guys add the two new? I think I'm overthinking it and that's why I messed up.
import SpriteKit
import GameplayKit
import CoreMotion
class GameScene: SKScene, SKPhysicsContactDelegate {
var starfield:SKEmitterNode!
var player:SKSpriteNode!
var scoreLabel:SKLabelNode!
var score:Int = 0 {
didSet {
scoreLabel.text = "Score: \(score)"
}
}
var gameTimer:Timer!
var possibleAliens = ["alien"]
//This is the "alien you earn +5 point from shooting. Im trying to get 2 new aliens to the scene, one that you lose -5 points from shooting and one you lose -10 on.
//I have tried to rewrite the codes to the two new, but they still earn +5 points from shooting all 3 types. What would you guys do and how?
let alienCategory:UInt32 = 0x1 << 1
let photonTorpedoCategory:UInt32 = 0x1 << 0
let motionManger = CMMotionManager()
var xAcceleration:CGFloat = 0
override func didMove(to view: SKView) {
starfield = SKEmitterNode(fileNamed: "Starfield")
starfield.position = CGPoint(x: 0, y: 1472)
starfield.advanceSimulationTime(10)
self.addChild(starfield)
starfield.zPosition = -1
player = SKSpriteNode(imageNamed: "shuttle")
player.position = CGPoint(x: self.frame.size.width / 2, y: player.size.height / 2 + 20)
self.addChild(player)
self.physicsWorld.gravity = CGVector(dx: 0, dy: 0)
self.physicsWorld.contactDelegate = self
scoreLabel = SKLabelNode(text: "Score: 0")
scoreLabel.position = CGPoint(x: 100, y: self.frame.size.height - 60)
scoreLabel.fontName = "AmericanTypewriter-Bold"
scoreLabel.fontSize = 36
scoreLabel.fontColor = UIColor.white
score = 0
self.addChild(scoreLabel)
gameTimer = Timer.scheduledTimer(timeInterval: 0.75, target: self, selector: #selector(addAlien), userInfo: nil, repeats: true)
motionManger.accelerometerUpdateInterval = 0.2
motionManger.startAccelerometerUpdates(to: OperationQueue.current!) { (data:CMAccelerometerData?, error:Error?) in
if let accelerometerData = data {
let acceleration = accelerometerData.acceleration
self.xAcceleration = CGFloat(acceleration.x) * 0.75 + self.xAcceleration * 0.25
}
}
}
func addAlien () {
possibleAliens = GKRandomSource.sharedRandom().arrayByShufflingObjects(in: possibleAliens) as! [String]
let alien = SKSpriteNode(imageNamed: possibleAliens[0])
let randomAlienPosition = GKRandomDistribution(lowestValue: 0, highestValue: 414)
let position = CGFloat(randomAlienPosition.nextInt())
alien.position = CGPoint(x: position, y: self.frame.size.height + alien.size.height)
alien.physicsBody = SKPhysicsBody(rectangleOf: alien.size)
alien.physicsBody?.isDynamic = true
alien.physicsBody?.categoryBitMask = alienCategory
alien.physicsBody?.contactTestBitMask = photonTorpedoCategory
alien.physicsBody?.collisionBitMask = 0
self.addChild(alien)
let animationDuration:TimeInterval = 6
var actionArray = [SKAction]()
actionArray.append(SKAction.move(to: CGPoint(x: position, y: -alien.size.height), duration: animationDuration))
actionArray.append(SKAction.removeFromParent())
alien.run(SKAction.sequence(actionArray))
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
fireTorpedo()
}
func fireTorpedo() {
self.run(SKAction.playSoundFileNamed("torpedo.mp3", waitForCompletion: false))
let torpedoNode = SKSpriteNode(imageNamed: "torpedo")
torpedoNode.position = player.position
torpedoNode.position.y += 5
torpedoNode.physicsBody = SKPhysicsBody(circleOfRadius: torpedoNode.size.width / 2)
torpedoNode.physicsBody?.isDynamic = true
torpedoNode.physicsBody?.categoryBitMask = photonTorpedoCategory
torpedoNode.physicsBody?.contactTestBitMask = alienCategory
torpedoNode.physicsBody?.collisionBitMask = 0
torpedoNode.physicsBody?.usesPreciseCollisionDetection = true
self.addChild(torpedoNode)
let animationDuration:TimeInterval = 0.3
var actionArray = [SKAction]()
actionArray.append(SKAction.move(to: CGPoint(x: player.position.x, y: self.frame.size.height + 10), duration: animationDuration))
actionArray.append(SKAction.removeFromParent())
torpedoNode.run(SKAction.sequence(actionArray))
}
func didBegin(_ contact: SKPhysicsContact) {
var firstBody:SKPhysicsBody
var secondBody:SKPhysicsBody
if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
firstBody = contact.bodyA
secondBody = contact.bodyB
}else{
firstBody = contact.bodyB
secondBody = contact.bodyA
}
if (firstBody.categoryBitMask & photonTorpedoCategory) != 0 && (secondBody.categoryBitMask & alienCategory) != 0 {
torpedoDidCollideWithAlien(torpedoNode: firstBody.node as! SKSpriteNode, alienNode: secondBody.node as! SKSpriteNode)
}
}
func torpedoDidCollideWithAlien (torpedoNode:SKSpriteNode, alienNode:SKSpriteNode) {
let explosion = SKEmitterNode(fileNamed: "Explosion")!
explosion.position = alienNode.position
self.addChild(explosion)
self.run(SKAction.playSoundFileNamed("explosion.mp3", waitForCompletion: false))
torpedoNode.removeFromParent()
alienNode.removeFromParent()
self.run(SKAction.wait(forDuration: 2)) {
explosion.removeFromParent()
}
score += 5
}
override func didSimulatePhysics() {
player.position.x += xAcceleration * 50
if player.position.x < -20 {
player.position = CGPoint(x: self.size.width + 20, y: player.position.y)
}else if player.position.x > self.size.width + 20 {
player.position = CGPoint(x: -20, y: player.position.y)
}
}
override func update(_ currentTime: TimeInterval) {
// Called before each frame is rendered
}
}

Answer 1

I wouldn't recommend following this answer if your game becomes more complex. Normally I would say put the aliens in subclasses initialized with their own categorybitmasks and other properties, but to avoid modifying your code too much I just changed the addAlien() method and didBeginContact method. Each alien has its own categoryBitMask and textureName.
let alienCategories:[UInt32] = [(0x1 << 1),(0x1 << 2),(0x1 << 3)]
let alienTextureNames:[String] = ["alien1","alien2","alien3"]
This will make a random Alien using the values in the collections above
func addAlien () {
//Random index between 0 and 2 changing the texture and category bitmask
let index = Int.random(in: 0...2)
let textureName = alienTextureNames[index]
let alien = SKSpriteNode(imageNamed: textureName)
//Use Int.random() if you don't want a CGFLoat
let xPos = CGFloat.random(in: 0...414)
let yPos = frame.size.height + alien.size.height
alien.position = CGPoint(x: xPos, y: yPos)
alien.physicsBody = SKPhysicsBody(rectangleOf: alien.size)
alien.physicsBody?.isDynamic = true
alien.physicsBody?.categoryBitMask = alienCategories[index]
alien.physicsBody?.contactTestBitMask = photonTorpedoCategory
alien.physicsBody?.collisionBitMask = 0
self.addChild(alien)
let moveAction = SKAction.moveTo(y: -alien.size.height, duration: 6)
alien.run(moveAction, completion: { alien.removeFromParent() })
}
func didBegin(_ contact: SKPhysicsContact) {
var firstBody:SKPhysicsBody
var secondBody:SKPhysicsBody
if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
firstBody = contact.bodyA
secondBody = contact.bodyB
}else{
firstBody = contact.bodyB
secondBody = contact.bodyA
}
if firstBody.categoryBitMask == photonTorpedoCategory && secondBody.categoryBitMask == alienCategories[0] {
torpedoDidCollideWithAlien(torpedoNode: firstBody.node as! SKSpriteNode, alienNode: secondBody.node as! SKSpriteNode)
score += 5
}else if firstBody.categoryBitMask == photonTorpedoCategory && secondBody.categoryBitMask == alienCategories[1] {
torpedoDidCollideWithAlien(torpedoNode: firstBody.node as! SKSpriteNode, alienNode: secondBody.node as! SKSpriteNode)
score -= 5
}else if firstBody.categoryBitMask == photonTorpedoCategory && secondBody.categoryBitMask == alienCategories[2] {
torpedoDidCollideWithAlien(torpedoNode: firstBody.node as! SKSpriteNode, alienNode: secondBody.node as! SKSpriteNode)
score -= 10
}
}
Change the torpedoNode.physicsBody?.contactTestBitMask = alienCategory line in the fireTorpedo method to alien.physicsBody?.contactTestBitMask = (alienCategories[0] | alienCategories[1] | alienCategories[2])