我用这段代码生成一个随机数:

//
//  FactModel.swift
//  Collection
//
//  Created by Ahmadreza Shamimi on 6/11/16.
//  Copyright © 2016 Ahmadreza Shamimi. All rights reserved.
//

import GameKit

struct FactModel {

    let fun  = ["I love swift","My name is Ahmadreza","I love coding" ,"I love PHP","My name is ALireza","I love Coding too"]


    func getRandomNumber() -> String {

        let randomNumber  = GKRandomSource.sharedRandom().nextIntWithUpperBound(fun.count)

        return fun[randomNumber]
    }
}

你可以像这样使用GeneratorOf:

var fibs = ArraySlice([1, 1])
var fibGenerator = GeneratorOf{
    _ -> Int? in
    fibs.append(fibs.reduce(0, combine:+))
    return fibs.removeAtIndex(0)
}

println(fibGenerator.next())
println(fibGenerator.next())
println(fibGenerator.next())
println(fibGenerator.next())
println(fibGenerator.next())
println(fibGenerator.next())

编辑:为Swift 3.0更新

arc4random在Swift中工作得很好，但基本函数仅限于32位整数类型(Int在iPhone 5S和现代mac上是64位)。下面是一个泛型函数，用于表示可以用整型字面值表示的类型的随机数:

public func arc4random<T: ExpressibleByIntegerLiteral>(_ type: T.Type) -> T {
    var r: T = 0
    arc4random_buf(&r, MemoryLayout<T>.size)
    return r
}

我们可以使用这个新的泛型函数扩展UInt64，增加边界参数并减少模偏置。(这是从arc4random.c直接引用的)

public extension UInt64 {
    public static func random(lower: UInt64 = min, upper: UInt64 = max) -> UInt64 {
        var m: UInt64
        let u = upper - lower
        var r = arc4random(UInt64.self)

        if u > UInt64(Int64.max) {
            m = 1 + ~u
        } else {
            m = ((max - (u * 2)) + 1) % u
        }

        while r < m {
            r = arc4random(UInt64.self)
        }

        return (r % u) + lower
    }
}

这样我们就可以将Int64扩展为相同的参数，处理溢出:

public extension Int64 {
    public static func random(lower: Int64 = min, upper: Int64 = max) -> Int64 {
        let (s, overflow) = Int64.subtractWithOverflow(upper, lower)
        let u = overflow ? UInt64.max - UInt64(~s) : UInt64(s)
        let r = UInt64.random(upper: u)

        if r > UInt64(Int64.max)  {
            return Int64(r - (UInt64(~lower) + 1))
        } else {
            return Int64(r) + lower
        }
    }
}

为了让家庭更完整……

private let _wordSize = __WORDSIZE

public extension UInt32 {
    public static func random(lower: UInt32 = min, upper: UInt32 = max) -> UInt32 {
        return arc4random_uniform(upper - lower) + lower
    }
}

public extension Int32 {
    public static func random(lower: Int32 = min, upper: Int32 = max) -> Int32 {
        let r = arc4random_uniform(UInt32(Int64(upper) - Int64(lower)))
        return Int32(Int64(r) + Int64(lower))
    }
}

public extension UInt {
    public static func random(lower: UInt = min, upper: UInt = max) -> UInt {
        switch (_wordSize) {
            case 32: return UInt(UInt32.random(UInt32(lower), upper: UInt32(upper)))
            case 64: return UInt(UInt64.random(UInt64(lower), upper: UInt64(upper)))
            default: return lower
        }
    }
}

public extension Int {
    public static func random(lower: Int = min, upper: Int = max) -> Int {
        switch (_wordSize) {
            case 32: return Int(Int32.random(Int32(lower), upper: Int32(upper)))
            case 64: return Int(Int64.random(Int64(lower), upper: Int64(upper)))
            default: return lower
        }
    }
}

在所有这些之后，我们终于可以做这样的事情:

let diceRoll = UInt64.random(lower: 1, upper: 7)

我使用了下面的代码:

var k: Int = random() % 10;

Swift 4.2编辑

从Swift 4.2开始，你可以使用Swift自己的本地函数，而不是使用导入的C函数arc4random_uniform()。

// Generates integers starting with 0 up to, and including, 10
Int.random(in: 0 ... 10)

你也可以使用random(in:)来获取其他原始值的随机值;比如Int型，Double型，Float型，甚至Bool型。

Swift版本< 4.2

该方法将在给定的最小值和最大值之间生成一个随机Int值

func randomInt(min: Int, max: Int) -> Int {
    return min + Int(arc4random_uniform(UInt32(max - min + 1)))
}

斯威夫特4.2

拜拜导入Foundation C库arc4random_uniform()

// 1  
let digit = Int.random(in: 0..<10)

// 2
if let anotherDigit = (0..<10).randomElement() {
  print(anotherDigit)
} else {
  print("Empty range.")
}

// 3
let double = Double.random(in: 0..<1)
let float = Float.random(in: 0..<1)
let cgFloat = CGFloat.random(in: 0..<1)
let bool = Bool.random()

使用random(in:)从范围中生成随机数字。 randomElement()返回nil如果范围是空的，所以你打开返回的Int?用if let。 使用random(in:)生成随机Double、Float或CGFloat，使用random()返回随机Bool类型。

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