Collision Detection in SpriteKit + Swift

Question

I am making a simple Pong game using SpriteKit + Swift. Right now I am trying to detect when the ball hits the edge of the screen. When I run my code and the ball hits the edge of the screen, for some reason the score increases twice instead of once. For example the console reads

Player 1 has a score of: 1.
Player 1 has a score of: 2.

when I hit the right side of the screen once.

My code in the didBeginContact function:

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 == ballCategory && secondBody.categoryBitMask == leftSideCategory {
        player2Score++
        print("Player 2 has a score of: \(player2Score).")
    } else if firstBody.categoryBitMask == ballCategory && secondBody.categoryBitMask == rightSideCategory {
        player1Score++
        print("Player 1 has a score of: \(player1Score).")
    }

}

Answer 1

Set the firstBody.categoryBitMask to something other than ballCategory . Maybe something like deadBallCategory which is set to 0x0 (or 0, or however you define them, either way, set it to 0). Then, your firstBody (the ball) won't keep triggering your didBeginContact function. When you create a new ball to add to the scene, make sure to set the categoryBitMask to ballCategory (which it appears you do anyway).