小编Oli*_*nik的帖子

所以我需要从圆周边的随机点产生游戏敌人.这是我到目前为止的代码,感觉非常接近工作,但不是:

let enemy = SKShapeNode(circleOfRadius: 5)

func enemyGenerator() {

//takes an x value and calculates the corresponding y coordinate on the circle.
    func enemyYSpawnPosition(x: CGFloat) -> CGFloat {
        return sqrt(104006.25 - (x * x))
    }

//randomly selects an x value from a range of acceptable values.
    func enemyXSpawnPosition() -> CGFloat {
        func randRange (lower: Int , upper: Int) -> Int {
            return lower + Int(arc4random_uniform(UInt32(upper - lower + 1)))
        }
        var xValue = randRange(-2.5, 322.5)
        return CGFloat (xValue)
    }

//used …