sprite-kit - 如何在击中某些敌人后删除敌人？

Question

我试图在两次射击后删除一个敌人。这是我的 didBegin

func didBegin(_ contact: SKPhysicsContact) {

    var body1:SKPhysicsBody
    var body2:SKPhysicsBody

    if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
        body1 = contact.bodyA
        body2 = contact.bodyB
    }else{
        body1 = contact.bodyB
        body2 = contact.bodyA
    }


    if body1.categoryBitMask == PhysicsCatagory.Bullet && body2.categoryBitMask == PhysicsCatagory.Enemy{
        //if the bullet has hit the enemy
        if body2.node != nil {
            spawnSplatter(spawnPosition: body2.node!.position)
            body1.node?.removeFromParent()
            body2.node?.removeFromParent()
        }

这会在击中一次后删除敌人，有人可以告诉我如何在击中两次后删除敌人吗？

Answer 1

通常，尝试删除 didBegin(_ contact: 的节点这不是一个好主意，因为您可能与节点有多个接触，这些接触在第一次接触后变为 nil，这可能会导致崩溃。

var bulletCounter : Int = 0
var nodesToRemove = [SKNode]()

func didBegin(_ contact: SKPhysicsContact) {
    var body1:SKPhysicsBody
    var body2:SKPhysicsBody
    if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
        body1 = contact.bodyA
        body2 = contact.bodyB
    }else{
        body1 = contact.bodyB
        body2 = contact.bodyA
    }
    if body1.categoryBitMask == PhysicsCatagory.Bullet && body2.categoryBitMask == PhysicsCatagory.Enemy{
        //if the bullet has hit the enemy
        bulletCounter += 1
        nodesToRemove.append(body1.node!) // remove always the bullet
        switch bulletCounter {
        case 2: 
           nodesToRemove.append(body2.node!) // remove enemy
           bulletCounter = 0
        default:break 
        }
    }
}
override func didFinishUpdate()
{
    nodesToRemove.forEach(){$0.removeFromParent()}
    nodesToRemove = [SKNode]()
}

如果您有 1 个敌人，此示例可能会很有用。如果你有更多敌人，你可以创建一个 bulletCounter属性到您的敌人类别或存储 bulletCounter SKNode 内的值userData属性:

首先创建字典:

enemy.userData = NSMutableDictionary()
enemy.userData?.setObject(0, forKey: "bulletCounter")

在游戏过程中获取/分配你的值(value):

if let bulletCounter = self.userData?.object(forKey: "bulletCounter") {
   var counter = bulletCounter as! Int
   counter += 1
   self.userData?.setObject(counter, forKey: "bulletCounter" as NSCopying)
}