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尋找一種方法,每隔30秒在屏幕中心產生一個新的精靈。它必須受到重力的影響。斯威夫特2:每30秒產生一個新的精靈
我設法產生了精靈,但是當試圖設置affectedByGravity爲true時,遊戲崩潰。
「致命錯誤:意外發現零而展開的可選值」
這是我得到的代碼:
self.timer = NSTimer.scheduledTimerWithTimeInterval(2.0, target: self, selector: "spawningCars", userInfo: nil, repeats: true)
func spawningCars() {
let enemyTowardsTexture = SKTexture(imageNamed: "player")
let enemyTowards = SKSpriteNode(texture: enemyTowardsTexture)
enemyTowards.position = ourCamera.position
enemyTowards.physicsBody!.affectedByGravity = true
self.addChild(enemyTowards)
print("spawning car right")
timer.invalidate()
resetTimer()
}
func resetTimer() {
self.timer = NSTimer.scheduledTimerWithTimeInterval(5.0, target: self, selector: "spawningCars", userInfo: nil, repeats: true)
}