Basic Swift SpriteKit Collisions using PhysicsBodys - swift

Question

The problem: I seem to be having a little trouble getting my player to collide with a coin, and adding +1 to a coinLabel upon the collision. The player should continue moving after coming in contact with the coin.
What I have now: With the code I have now, the player travels through the coin, but there is no collision that takes place and +1 isn't added to the coin label.
I am still learning the swift language, so I appreciate any help that is given.
Code:
struct ColliderType {
static let playerCategory: UInt32 = 0x1 << 0
static let boundary: UInt32 = 0x1 << 1
​
​static let coinCategory: UInt32 = 0x1 << 2
​
​static let bodyA: UInt32 = 0x1 << 4
​
​static let bodyB: UInt32 = 0x1 << 8
}
​override func didMoveToView(view: SKView) {
​
var coinInt = 0
​
​
​
​self.physicsWorld.gravity = CGVectorMake(0.0, -7.0)
physicsWorld.contactDelegate = self
player = SKSpriteNode(imageNamed: "player")
player.zPosition = 1
player.position = CGPoint(x: CGRectGetMidX(self.frame), y: CGRectGetMidY(self.frame))
player.physicsBody = SKPhysicsBody(circleOfRadius: player.size.width / 5.12)
player.physicsBody?.dynamic = true
player.physicsBody?.allowsRotation = false
self.addChild(player)
generateCoins()
​
​
coin = SKSpriteNode( imageNamed: "coin")
coin.physicsBody? = SKPhysicsBody(circleOfRadius: coin.size.height / 10)
coin.physicsBody?.dynamic = false
coin.physicsBody?.allowsRotation = false
coin.zPosition = 1
​self.addChild(coin)
​
player.physicsBody?.categoryBitMask = ColliderType.playerCategory
​player.physicsBody?.contactTestBitMask = ColliderType.boundary
player.physicsBody?.collisionBitMask = ColliderType.coinCategory | ColliderType.boundary
coin.physicsBody?.categoryBitMask = ColliderType.coinCategory
coin.physicsBody?.contactTestBitMask = ColliderType.playerCategory
coin.physicsBody?.collisionBitMask = ColliderType.playerCategory
func didPlayerCollideWithCoin(player: SKSpriteNode, coin: SKSpriteNode) {
self.coin.removeFromParent()
self.coin += 1
coinLabel.text = "\(coinInt)"
}
​
​
​
​func generateCoins() {
if(self.actionForKey("spawning") != nil){return}
let coinTimer = SKAction.waitForDuration(7, withRange: 2)
let spawnCoin = SKAction.runBlock {
self.coin = SKSpriteNode( imageNamed: "coin")
self.coin.physicsBody = SKPhysicsBody(circleOfRadius: self.coin.size.height / 10)
self.coin.name = "coin"
self.coin.physicsBody?.dynamic = false
self.coin.physicsBody?.allowsRotation = false
var coinPosition = Array<CGPoint>()
coinPosition.append((CGPoint(x:340, y:103)))
coinPosition.append((CGPoint(x:340, y:148)))
coinPosition.append((CGPoint(x:340, y:218)))
coinPosition.append((CGPoint(x: 340, y:343)))
let spawnLocation = coinPosition[Int(arc4random_uniform(UInt32(coinPosition.count)))]
let action = SKAction.repeatActionForever(SKAction.moveToX(+self.xScale, duration: 4.4))
self.coin.runAction(action)
self.coin.position = spawnLocation
self.addChild(self.coin)
print(spawnLocation)
}
let sequence = SKAction.sequence([coinTimer, spawnCoin])
self.runAction(SKAction.repeatActionForever(sequence), withKey: "spawning")
}
​​
func didBeginContact(contact:SKPhysicsContact) {
let bodyA: SKPhysicsBody = contact.bodyA
let bodyB: SKPhysicsBody = contact.bodyB
if ((bodyA.categoryBitMask == ColliderType.playerCategory) && (bodyB.categoryBitMask == ColliderType.coinCategory)){
didPlayerCollideWithCoin(bodyA.node as! SKSpriteNode, coin: bodyB.node as! SKSpriteNode)
}
​
​}

Answer 1

You could try leaving your contactTestBitmasks the same but remove the collisionBitmasks between the player and coin:
player.physicsBody?.categoryBitMask = ColliderType.playerCategory
​player.physicsBody?.contactTestBitMask = ColliderType.boundary
player.physicsBody?.collisionBitMask = ColliderType.boundary
coin.physicsBody?.categoryBitMask = ColliderType.coinCategory
coin.physicsBody?.contactTestBitMask = ColliderType.playerCategory
This way, when the player collides with a coin it will register, but it wont "bounce off" and will continue moving in the same direction.
*Note: Using this MAY require you to use the
func didBeginContact(contact: SKPhysicsContact) {
method instead of
func didPlayerCollideWithCoin(player: SKSpriteNode, coin: SKSpriteNode) {
But I recommend trying it with the didPlayerCollideWithCoin() method first.
In case you need it, it is implemented like this:
func didBeginContact(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 == playerCategory && secondBody.categoryBitMask == coinCategory {
print("Your player passes through the coin")
score = score + 1
}
}
For more details see this tutorial from Ray Wenderlich:
https://www.raywenderlich.com/123393/how-to-create-a-breakout-game-with-sprite-kit-and-swift