Basic Swift SpriteKit Collisions using PhysicsBodys

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)

}
            
}

Why (circleOfRadius: coinOne.size.height / 10) shouldn't it be (circleOfRadius: coinOne.size.height / 2) ? — T. Benjamin Larsen
I thought that the number that comes after the " / " controls how large the physicsBody is? Like if you use / 2, or /3 the physicsBody will be larger compared to using a higher number. I could be wrong. — P.Dane
The radius (which is what you're after) is the diameter/2. If the height of your coin == the coin's diameter (which it probably does) then this value divided by 2 probably gives you the size you're after. — T. Benjamin Larsen
Make sure you're clear about whether or not your want collisions, contacts or both. I suspect you want the player and the coin to contact but not to collide? — Steve Ives
Sorry for the late reply. Yes, I would like the player and coin to contact but not collide. — P.Dane

hb22 hb22 · Accepted Answer · 2016-06-02T00:22:58

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

Basic Swift SpriteKit Collisions using PhysicsBodys

1 Answers