0 到 1 之間的 Swift 隨機浮點數

Question

在 Swift 中，我試圖在 0 和 1 之間獲得一個隨機浮點數，但我似乎無法使類型轉換起作用。

func randomCGFloat() -> CGFloat {
    return CGFloat(arc4random()) / UINT32_MAX
}

我收到“CGFloat”無法轉換為“UInt8”錯誤

運行 Xcode 6。

Answer 1

這是對Int、Double、Float、CGFloat隨機數的擴展

Swift 3 & 4 & 5 語法

import Foundation
import CoreGraphics

// MARK: Int Extension

public extension Int {

    /// Returns a random Int point number between 0 and Int.max.
    static var random: Int {
        return Int.random(n: Int.max)
    }

    /// Random integer between 0 and n-1.
    ///
    /// - Parameter n:  Interval max
    /// - Returns:      Returns a random Int point number between 0 and n max
    static func random(n: Int) -> Int {
        return Int(arc4random_uniform(UInt32(n)))
    }

    ///  Random integer between min and max
    ///
    /// - Parameters:
    ///   - min:    Interval minimun
    ///   - max:    Interval max
    /// - Returns:  Returns a random Int point number between 0 and n max
    static func random(min: Int, max: Int) -> Int {
        return Int.random(n: max - min + 1) + min

    }
}

// MARK: Double Extension

public extension Double {

    /// Returns a random floating point number between 0.0 and 1.0, inclusive.
    static var random: Double {
        return Double(arc4random()) / 0xFFFFFFFF
    }

    /// Random double between 0 and n-1.
    ///
    /// - Parameter n:  Interval max
    /// - Returns:      Returns a random double point number between 0 and n max
    static func random(min: Double, max: Double) -> Double {
        return Double.random * (max - min) + min
    }
}

// MARK: Float Extension

public extension Float {

    /// Returns a random floating point number between 0.0 and 1.0, inclusive.
    static var random: Float {
        return Float(arc4random()) / 0xFFFFFFFF
    }

    /// Random float between 0 and n-1.
    ///
    /// - Parameter n:  Interval max
    /// - Returns:      Returns a random float point number between 0 and n max
    static func random(min: Float, max: Float) -> Float {
        return Float.random * (max - min) + min
    }
}

// MARK: CGFloat Extension

public extension CGFloat {

    /// Randomly returns either 1.0 or -1.0.
    static var randomSign: CGFloat {
        return (arc4random_uniform(2) == 0) ? 1.0 : -1.0
    }

    /// Returns a random floating point number between 0.0 and 1.0, inclusive.
    static var random: CGFloat {
        return CGFloat(Float.random)
    }

    /// Random CGFloat between 0 and n-1.
    ///
    /// - Parameter n:  Interval max
    /// - Returns:      Returns a random CGFloat point number between 0 and n max
    static func random(min: CGFloat, max: CGFloat) -> CGFloat {
        return CGFloat.random * (max - min) + min
    }
}

用 ：

let randomNumDouble  = Double.random(min: 0.00, max: 23.50)
let randomNumInt     = Int.random(min: 56, max: 992)
let randomNumFloat   = Float.random(min: 6.98, max: 923.09)
let randomNumCGFloat = CGFloat.random(min: 6.98, max: 923.09)

Answer 2

嘗試將除數初始化為浮點數，a la：

CGFloat(Float(arc4random()) / Float(UINT32_MAX))

Answer 3

快速 4.2 ：

let randomFloat = Float.random(in: 0..<1)

Answer 4

更新Sandy Chapman對 Swift 3的回答：

extension ClosedRange where Bound : FloatingPoint {
    public func random() -> Bound {
        let range = self.upperBound - self.lowerBound
        let randomValue = (Bound(arc4random_uniform(UINT32_MAX)) / Bound(UINT32_MAX)) * range + self.lowerBound
        return randomValue
    }
}

現在你可以說(-1.0...1.0).random() 。

編輯我想今天（Swift 4）我會寫這樣的東西：

extension ClosedRange where Bound : FloatingPoint {
    public func random() -> Bound {
        let max = UInt32.max
        return
            Bound(arc4random_uniform(max)) /
            Bound(max) *
            (upperBound - lowerBound) +
            lowerBound
    }
}

注意Swift 4.2 引入了原生隨機數生成，所有這些都沒有實際意義。

Answer 5

這里框架在 Swift 中生成隨機數數據方面做得很好： https : //github.com/thellimist/SwiftRandom/blob/master/SwiftRandom/Randoms.swift

public extension Int {
    /// SwiftRandom extension
    public static func random(lower: Int = 0, _ upper: Int = 100) -> Int {
        return lower + Int(arc4random_uniform(UInt32(upper - lower + 1)))
    }
}

public extension Double {
    /// SwiftRandom extension
    public static func random(lower: Double = 0, _ upper: Double = 100) -> Double {
        return (Double(arc4random()) / 0xFFFFFFFF) * (upper - lower) + lower
    }
}

public extension Float {
    /// SwiftRandom extension
    public static func random(lower: Float = 0, _ upper: Float = 100) -> Float {
        return (Float(arc4random()) / 0xFFFFFFFF) * (upper - lower) + lower
    }
}

public extension CGFloat {
    /// SwiftRandom extension
    public static func random(lower: CGFloat = 0, _ upper: CGFloat = 1) -> CGFloat {
        return CGFloat(Float(arc4random()) / Float(UINT32_MAX)) * (upper - lower) + lower
    }
}

Answer 6

下面是IntervalType類型的擴展，用於執行此操作：

extension IntervalType {
    public func random() -> Bound {
        let range = (self.end as! Double) - (self.start as! Double)
        let randomValue = (Double(arc4random_uniform(UINT32_MAX)) / Double(UINT32_MAX)) * range + (self.start as! Double)
        return randomValue as! Bound
    }
}

使用此擴展，您可以使用區間語法生成區間，然后在該區間中獲取隨機值：

(0.0...1.0).random()

添加

如果您希望對Int做同樣的事情，那么您可以在CollectionType協議上使用以下擴展：

extension CollectionType {
    public func random() -> Self._Element {
        if let startIndex = self.startIndex as? Int {
            let start = UInt32(startIndex)
            let end = UInt32(self.endIndex as! Int)
            return self[Int(arc4random_uniform(end - start) + start) as! Self.Index]
        }
        var generator = self.generate()
        var count = arc4random_uniform(UInt32(self.count as! Int))
        while count > 0 {
            generator.next()
            count = count - 1
        }
        return generator.next() as! Self._Element
    }
}

Int不使用IntervalType 。 他們使用Range代替。 在CollectionType類型上這樣做的好處是它會自動轉移到Dictionary和Array類型。

例子：

(0...10).random()               // Ex: 6
["A", "B", "C"].random()        // Ex: "B"
["X":1, "Y":2, "Z":3].random()  // Ex: (.0: "Y", .1: 2)

Answer 7

斯威夫特 5

let randomFloat = CGFloat.random(in: 0...1)

Answer 8

jmduke 建議的內容似乎可以在 Playground 中使用，但在功能上略有變化：

func randomCGFloat() -> Float {
    return Float(arc4random()) /  Float(UInt32.max)
}

以及為什么從 swift doc 和 drawag 指出的原因：類型轉換必須是顯式的，文檔中的示例是：

let three = 3
let pointOneFourOneFiveNine = 0.14159
let pi = Double(three) + pointOneFourOneFiveNine
// pi equals 3.14159, and is inferred to be of type Double

Answer 9

drand48()

如果你需要[雙]。 在 0 和 1 之間。僅此而已。

Answer 10

基於 YannickSteph 的回答

要使其適用於任何浮點類型，如Double 、 Float 、 CGFloat等，您可以為BinaryFloatingPoint類型進行擴展：

extension BinaryFloatingPoint {

    /// Returns a random floating point number between 0.0 and 1.0, inclusive.
    public static var random: Self {
        return Self(arc4random()) / 0xFFFFFFFF
    }

    /// Random double between 0 and n-1.
    ///
    /// - Parameter n:  Interval max
    /// - Returns:      Returns a random double point number between 0 and n max
    public static func random(min: Self, max: Self) -> Self {
        return Self.random * (max - min) + min
    }
}

Answer 11

細節

Xcode：9.2，Swift 4

解決方案

extension BinaryInteger {

    static func rand(_ min: Self, _ max: Self) -> Self {
        let _min = min
        let difference = max+1 - _min
        return Self(arc4random_uniform(UInt32(difference))) + _min
    }
}

extension BinaryFloatingPoint {

    private func toInt() -> Int {
        // https://stackoverflow.com/q/49325962/4488252
        if let value = self as? CGFloat {
            return Int(value)
        }
        return Int(self)
    }

    static func rand(_ min: Self, _ max: Self, precision: Int) -> Self {

        if precision == 0 {
            let min = min.rounded(.down).toInt()
            let max = max.rounded(.down).toInt()
            return Self(Int.rand(min, max))
        }

        let delta = max - min
        let maxFloatPart = Self(pow(10.0, Double(precision)))
        let maxIntegerPart = (delta * maxFloatPart).rounded(.down).toInt()
        let randomValue = Int.rand(0, maxIntegerPart)
        let result = min + Self(randomValue)/maxFloatPart
        return Self((result*maxFloatPart).toInt())/maxFloatPart
    }
}

用法

print("\(Int.rand(1, 20))")
print("\(Float.rand(5.231233, 44.5, precision: 3))")
print("\(Double.rand(5.231233, 44.5, precision: 4))")
print("\(CGFloat.rand(5.231233, 44.5, precision: 6))")

完整樣本

import Foundation
import CoreGraphics

func run() {
    let min = 2.38945
    let max = 2.39865
    for _ in 0...100 {
        let precision = Int.rand(0, 5)
        print("Precision: \(precision)")
        floatSample(min: Float(min), max: Float(max), precision: precision)
        floatSample(min: Double(min), max: Double(max), precision: precision)
        floatSample(min: CGFloat(min), max: CGFloat(max), precision: precision)
        intSample(min: Int(1), max: Int(10000))
        print("")
    }
}

private func printResult<T: Comparable>(min: T, max: T, random: T) {
    let result = "\(T.self) rand[\(min), \(max)] = \(random)"
    print(result)
}

func floatSample<T: BinaryFloatingPoint>(min: T, max: T, precision: Int) {
    printResult(min: min, max: max, random: T.rand(min, max, precision: precision))
}

func intSample<T: BinaryInteger>(min: T, max: T) {
    printResult(min: min, max: max, random: T.rand(min, max))
}

結果