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寻找一种方法,每隔30秒在屏幕中心产生一个新的精灵。它必须受到重力的影响。斯威夫特2:每30秒产生一个新的精灵
我设法产生了精灵,但是当试图设置affectedByGravity为true时,游戏崩溃。
“致命错误:意外发现零而展开的可选值”
这是我得到的代码:
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)
}