SpriteKit won't recognise contact - sprite-kit

Question

bellow is my code which for some reason won't recognise contact between two sprites, in this case, ninja and left or right wall. So my question is what am I missing? I add collision categories and assigned them accordingly
func didBegin(_ contact: SKPhysicsContact) {
let nodeB = contact.bodyB.node!
if nodeB.name == "RIGHT_WALL" {
print("right wall touched")
RightWallTouched = true
self.CurrentScore = self.CurrentScore + 1
}
if nodeB.name == "LEFT_WALL" {
print("left wall touched")
RightWallTouched = false
self.CurrentScore = self.CurrentScore + 1
}
self.CurrentScoreLabel.text = "\(self.CurrentScore)"
if nodeB.name == "SPIKE" {
self.GameStarted = false
if(CurrentScore > HighScore){
defaults.set(CurrentScore, forKey: self.HighScoreStorageKey)
defaults.synchronize()
self.HighScoreLabel.text = "\(self.defaults.integer(forKey: self.HighScoreStorageKey))"
}
endGame()
}
}
func CreateNinja(){
let ninjaTexture = SKTexture(imageNamed: "ninja-right.png")
ninjaTexture.filteringMode = .nearest
self.ninja = SKSpriteNode(texture: ninjaTexture)
self.ninja!.physicsBody = SKPhysicsBody(texture: ninjaTexture, size: ninja!.size)
self.ninja?.name = "NINJA"
self.ninja!.physicsBody?.isDynamic = false
self.ninja!.physicsBody?.allowsRotation = false
self.ninja!.physicsBody?.restitution = 0.6
self.ninja!.physicsBody?.mass = 0.430 // m = 430g
self.ninja!.position = CGPoint(x: self.frame.size.width / 2 , y: self.frame.size.height/5)
self.ninja!.physicsBody?.categoryBitMask = ninjaCollisionCategory
self.ninja!.physicsBody?.contactTestBitMask = 0
self.ninja!.physicsBody?.collisionBitMask = wallCollisionCategory
self.addChild(self.ninja!)
}
func CreateWall(){
let topwall = SKSpriteNode()
topwall.name = "TOP_WALL"
topwall.physicsBody = SKPhysicsBody(rectangleOf: CGSize(width: self.frame.size.width, height: 5))
topwall.physicsBody?.categoryBitMask = wallCollisionCategory
topwall.physicsBody?.isDynamic = false
topwall.physicsBody?.restitution = 0.6
topwall.position = CGPoint(x: self.frame.size.width / 2.0 , y: self.frame.size.height)
topwall.physicsBody?.friction = 0
topwall.zPosition = 4
self.addChild(topwall)
let leftwall = SKSpriteNode(color: UIColor.black, size: CGSize(width: 20, height: self.frame.size.height))
leftwall.name = "LEFT_WALL"
leftwall.physicsBody = SKPhysicsBody(rectangleOf: CGSize(width: 20, height: self.frame.size.height))
leftwall.physicsBody?.categoryBitMask = wallCollisionCategory
leftwall.physicsBody?.contactTestBitMask = 0
leftwall.physicsBody?.isDynamic = false
leftwall.position = CGPoint(x: 0 , y: self.frame.size.height / 2.0)
leftwall.zPosition = 4
leftwall.physicsBody?.restitution = 1.0
leftwall.physicsBody?.friction = 0
self.addChild(leftwall)
let rightwall = SKSpriteNode(color: UIColor.black, size: CGSize(width: 20, height: self.frame.size.height))
rightwall.name = "RIGHT_WALL"
rightwall.physicsBody = SKPhysicsBody(rectangleOf: CGSize(width: 20, height: self.frame.size.height))
rightwall.physicsBody?.categoryBitMask = wallCollisionCategory
rightwall.physicsBody?.contactTestBitMask = 0
rightwall.physicsBody?.isDynamic = false
rightwall.physicsBody?.restitution = 1.0
rightwall.physicsBody?.friction = 0
rightwall.position = CGPoint(x: self.frame.size.width , y: self.frame.size.height / 2.0)
rightwall.zPosition = 4
self.addChild(rightwall)
}

Answer 1

A more common way to do the collision function would be something like this
func didBegin(_ contact: SKPhysicsContact) {
let firstBody: SKPhysicsBody
let secondBody: SKPhysicsBody
if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
firstBody = contact.bodyA
secondBody = contact.bodyB
} else {
firstBody = contact.bodyB
secondBody = contact.bodyA
}
// Ninja hit wall or wall hit ninja
if (firstBody.categoryBitMask == ninjaCollisionCategory) && (secondBody.categoryBitMask == wallCollisionCategory) {
// Do something for all walls
...
// you can also check the name for some specific wall e.g.
if secondBody.node?.name == "RIGHT_WALL" {
// hit right wall
}
}
}
You also need to set the delegate in didMoveToView
physicsWorld.contactDelegate = self
and should probably set your ninja sprite physics body to dynamic
ninja?.physicsBody?.isDynamic = true // You can also remove this line as its set to true by default
Finally, as good practice, try to follow the Swift guidelines, your functions and properties should start with small letters not capital letters e.g
var currentScore = 0
func createNinja() { ... }
Hope this helps