swift - 当使用 SpriteKit 同时与两个节点发生碰撞时，我如何选择我想要联系的节点？

Question

我有一个用 Swift 3 编码的 iOS 应用程序，其中一个球被射出并从屏幕上的砖 block 上弹开。如果我的砖 block 是一个 PhysicsBody(矩形)，我无法轻易确定砖 block 的哪一侧/角被击中。我决定不这样做，而是让积木的每一面都有自己独立的节点。我现在遇到的问题是，球不能同时与两个节点(比如左侧和底部)接触。每次与球接触后，我都会降低砖 block 的值(value)，而这又会使这一次击球的值(value)降低 2。我怎样才能做到，如果一个球击中两个节点，只执行一个接触的代码？

有时下面的代码会执行两次，球两次都与两个 brickNode 接触。

func didBegin(_ contact: SKPhysicsContact) {
    var firstBody:SKPhysicsBody
    var secondBody:SKPhysicsBody

    let countPoint = true

    if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
        firstBody = contact.bodyA
        secondBody = contact.bodyB
    } else {
        firstBody = contact.bodyB
        secondBody = contact.bodyA
    }

    if (firstBody.categoryBitMask & ballCategory) != 0 {
        if (firstBody.node != nil && secondBody.node != nil){
            if (secondBody.categoryBitMask & brickCategory) != 0  {
                ballDidHitBrick(ballNode: firstBody.node as! SKShapeNode, brickNode: secondBody.node as! SKShapeNode, decreasePoint: countPoint)
            } else if (secondBody.categoryBitMask & roofCategory) != 0 || (secondBody.categoryBitMask & rightWallCategory) != 0 || (secondBody.categoryBitMask & leftWallCategory) != 0 || (secondBody.categoryBitMask & bottomCategory) != 0 {
                ballDidHitWall(ballNode: firstBody.node as! SKShapeNode, wallNode: secondBody.node as! SKShapeNode)
            } else {
                //Nothing as of yet
            }
        }
    }
}

Answer 1

所以按照史蒂夫上面所说的，我实现了下面的代码，我不再每次更新都有双重联系人:

if !bricksHit.contains("\(secondBody.node?.name ?? ""), \(firstBody.node?.name ?? "")") {
    //If ball hasnt hit the object more than once
    bricksHit.append("\(secondBody.node?.name ?? ""), \(firstBody.node?.name ?? "")")

    ballDidHitBrick(ballNode: firstBody.node as! SKShapeNode, brickNode: secondBody.node as! SKShapeNode, decreasePoint: countPoint, contact: contact)
}

我还在下面添加了我的代码，每次更新后都会清除 bircksHit:

override func didFinishUpdate() {
    bricksHit.removeAll()
}