Swift Spritekit I detect a collison but it reads the collision mulitple times

Question

AppImage I have a wall of 4 rectangles that are different colors, to pass through the wall the color of the ball has to match that of the rectangle on the wall. The ball will pass through the wall, and a new wall will appear. However, when I detect this collision I get multiple collision readings. I have tested this by printing dead or alive, and it prints both or more many times.

func didBegin(_ contact: SKPhysicsContact) {

    if let nodeA = contact.bodyA.node as? SKShapeNode, let nodeB = contact.bodyB.node as? SKShapeNode {
        if nodeA.fillColor != nodeB.fillColor {
            print("DEAD")
        }
        else {
            print("Alive")
        }
    }
}      

please help!!!

Answer 1

Yep - this happens. The way to handle it (you can't get sprite-kit to NOT call didBegin multiple times in some circumstances) is to make sure that your contact code accommodates this and that handling the contract multiple times does not cause a problem (such as adding to the score multiple times, removing multiple lives, trying to access a node or physicsBody that has been removed etc).

There is a discussion here: Sprite-Kit registering multiple collisions for single contact

Some things you can do include:

• If you remove a node that is contacted, check for it being nil before you remove it (for the duplicate contacts)
• Add the node to a set and then remove all the nodes in the set in didFinishUpdate
• Add an 'inactive' flag' to the node's userData
• Make the node a subclass of SKSpriteNode and add an inactive property
• Etc etc.