Simplifying collision and player death in SpriteKit - ios

Question

I want to add a bunch of different rocks and other dangerous objects that the player can collide with and die. How would I do this effectively? Now if I would copy paste these functions, it would surely work. But it seems like a huge amount of unnecessary code.
Sidenote: I'm very new to xcode, swift 2 & Sprite-kit.
func didBeginContact(contact: SKPhysicsContact) {
let firstBody : SKPhysicsBody = contact.bodyA
let secondBody : SKPhysicsBody = contact.bodyB
if ((firstBody.categoryBitMask == PhysicsCategory.Rock) && (secondBody.categoryBitMask == PhysicsCategory.Bullet) || (firstBody.categoryBitMask == PhysicsCategory.Bullet) && (secondBody.categoryBitMask == PhysicsCategory.Rock)) {
CollisionWithBullet(firstBody.node as! SKSpriteNode, Bullet: secondBody.node as! SKSpriteNode)
}
if ((firstBody.categoryBitMask == PhysicsCategory.Rock) && (secondBody.categoryBitMask == PhysicsCategory.Player) || (firstBody.categoryBitMask == PhysicsCategory.Player) && (secondBody.categoryBitMask == PhysicsCategory.Rock)) {
CollisionWithPlayer(firstBody.node as! SKSpriteNode, Player: secondBody.node as! SKSpriteNode)
}
}
func CollisionWithPlayer(Rock: SKSpriteNode, Player: SKSpriteNode){
let ScoreDefault = NSUserDefaults.standardUserDefaults()
ScoreDefault.setValue(Score, forKey: "Score")
ScoreDefault.synchronize()
let HighscoreDefault = NSUserDefaults.standardUserDefaults()
if (HighscoreDefault.valueForKey("Highscore") != nil){
Highscore = HighscoreDefault.valueForKey("Highscore") as! NSInteger
} else {
Highscore = 0
}
if (Score > Highscore){
let HighscoreDefault = NSUserDefaults.standardUserDefaults()
HighscoreDefault.setValue(Score, forKey: "Highscore")
}
self.view?.presentScene(EndScene())
ScoreLabel.removeFromSuperview()
}

Answer 1

So what you're likely looking for here is the bitwise OR operator and the bitwise AND operator.
With SpriteKit, physicsBodies can have multiple categories assigned to them. For instance, if we have the following categories set up:
enum CollisionCategories : UInt32 {
case Player = 1
case Enemy = 2
case Rock = 4
case Bullet = 8
}
we can set up the player category and contact bitmasks as follows:
let player = SKSpriteNode(color: UIColor.blackColor(), size: CGSize(width: 50, height: 50))
player.physicsBody = SKPhysicsBody(rectangleOfSize: player.size)
player.physicsBody?.categoryBitMask = CollisionCategories.Player.rawValue
player.physicsBody?.contactTestBitMask = CollisionCategories.Enemy.rawValue
and two enemy category and contact bitmasks as follows:
let rockEnemy = SKSpriteNode(color: UIColor.greenColor(), size: CGSize(width: 25, height: 25))
rockEnemy.physicsBody = SKPhysicsBody(rectangleOfSize: rockEnemy.size)
rockEnemy.physicsBody?.categoryBitMask = CollisionCategories.Enemy.rawValue | CollisionCategories.Rock.rawValue
rockEnemy.physicsBody?.contactTestBitMask = CollisionCategories.Player.rawValue
let bulletEnemy = SKSpriteNode(color: UIColor.redColor(), size: CGSize(width: 25, height: 25))
bulletEnemy.physicsBody = SKPhysicsBody(rectangleOfSize: bulletEnemy.size)
bulletEnemy.physicsBody?.categoryBitMask = CollisionCategories.Enemy.rawValue | CollisionCategories.Bullet.rawValue
bulletEnemy.physicsBody?.contactTestBitMask = CollisionCategories.Player.rawValue
Notice that on setting the category bitmasks, I am using the bitwise OR operator ('|'). This is a nice way of setting the bitmasks to two different categories at the same time. This way, a sprite can be both a rock and an enemy or a bullet and an enemy, etc.
See the image below for an idea of what is happening bitwise under the hood.
In our contact detection function, we can use the bitwise AND operator ('&') to see if our contact possesses a certain category.
func didBeginContact(contact: SKPhysicsContact) {
let firstBody : SKPhysicsBody = contact.bodyA
let secondBody : SKPhysicsBody = contact.bodyB
if (firstBody.categoryBitMask & CollisionCategories.Player.rawValue == CollisionCategories.Player.rawValue &&
secondBody.categoryBitMask & CollisionCategories.Enemy.rawValue == CollisionCategories.Enemy.rawValue) {
print("The collision was between the Player and an Enemy")
}
else if (firstBody.categoryBitMask & CollisionCategories.Enemy.rawValue == CollisionCategories.Enemy.rawValue &&
secondBody.categoryBitMask & CollisionCategories.Player.rawValue == CollisionCategories.Player.rawValue) {
print("The collision was between the Player and an Enemy")
}
}
This way, you can have enemies with multiple categories, but you can always do one check to see if a node is in fact an enemy, regardless of what other categories they might possess.