Swift rand()不是随机的

main.swift：

import Foundation

var player = Player()

for _ in 1..6 {
    println(player.kick())
}

player.swift：

import Foundation

class Player {
    var health = 25
    var xp = 15
    var upgrades = ["kick": 0,"punch": 0]

    func kick() -> Int {
        let range = (3,7)
        let damage = Int(rand()) % (range.1 - range.0) + range.0 + 1
        return damage
    }

    func punch() -> Int {
        let range = (4,6)
        let damage = Int(rand()) % (range.1 - range.0) + range.0 + 1
        return damage
    }
}

每次运行代码时,都会记录这些数字：

7
5
5
6
6

我也试过这个：Int(arc4random(range.1 – range.0))range.0 1但它说它找不到接受提供的参数的重载

我不知道为什么会发生这种情况.我很感激一些帮助,谢谢！