Swift 4.2及更高版本

Question

我在https://www.hackingwithswift.com/read/35/2/generating-random-numbers-in-ios-8-and-earlier中读到，生成随机数的最佳方法是使用

    let r = arc4random_uniform(UInt32(_names.count))
    let name : String = _names[Int(r)]

但似乎很奇怪我必须投两次以获得一个随机数，我应该怎么做以避免投射？

Answer 1

这实际上取决于你想要避免多少铸造。你可以简单地将它包装在一个函数中：

func random(max maxNumber: Int) -> Int {
    return Int(arc4random_uniform(UInt32(maxNumber)))
}

那么你只需做一次丑陋的施法。无处不在你需要一个最大数字的随机数：

let r = random(max: _names.count)
let name: String = _names[r]

作为旁注，由于这是Swift，因此您的属性不需要_。

Answer 2

我真的很喜欢使用此扩展程序

extension Int {
    init(random range: Range<Int>) {

        let offset: Int
        if range.startIndex < 0 {
            offset = abs(range.startIndex)
        } else {
            offset = 0
        }

        let min = UInt32(range.startIndex + offset)
        let max = UInt32(range.endIndex   + offset)

        self = Int(min + arc4random_uniform(max - min)) - offset
    }
}

现在，您可以生成指示范围的随机Int

let a = Int(random: 1...10) // 3
let b = Int(random: 0..<10) // 6
let c = Int(random: 0...100) // 31
let d = Int(random: -10...3) // -4

Answer 3

你可以使用gameplaykit

let random = GKRandomDistribution(lowestValue: 0, highestValue: 100)
let r = random.nextInt()

Answer 4

来自Luca的修改后的答案，写在Swift 4中作为扩展名

/// Returns random number within given range, upper bound included, eg. -1...0 = [-1, 0, 1]
extension CountableClosedRange where Bound == Int
{
    var random: Int
    {
        let range = self
        let offset: Int = range.lowerBound < 0 ? abs(range.lowerBound) : 0
        let min = UInt32(range.lowerBound + offset)
        let max = UInt32(range.upperBound + offset)
        let randomNumber = Int(min + arc4random_uniform(max - min + 1)) - offset

        return randomNumber
    }
}

/// Returns random number within given range, upper bound not included, eg. -1...0 = [-1, 0]
extension CountableRange where Bound == Int
{
    var random: Int
    {
        let range = self
        let offset: Int = range.lowerBound < 0 ? abs(range.lowerBound) : 0
        let min = UInt32(range.lowerBound + offset)
        let max = UInt32(range.upperBound + offset)
        let randomNumber = Int(min + arc4random_uniform(max - min)) - offset

        return randomNumber
    }
}

示例：

(0...10).random
(0..<10).random

Answer 5

Swift 4.2及更高版本

您可以初始化随机元素：

let randomInt = Int.random(in: 0...1)
let randomDouble = Double.random(in: 0...1)

您还可以从类似的集合中获取随机元素

let randomInt = (0...9).randomElement()

另外，您还可以在数组上使用另一种便捷的方法来洗牌，这可能是您需要的：

let shuffled = [1, 2, 3, 4].shuffled()

Answer 6

或者你可以使用

 let name : String = _names[ Int(arc4random()) % _names.count ]

在Swift中生成一个随机数

6 个答案:

Swift 4.2及更高版本