SwifterSwift有这个实现

/// SwifterSwift: Create a new random string of given length.
///
///     String(randomOfLength: 10) -> "gY8r3MHvlQ"
///
/// - Parameter length: number of characters in string.
init(randomOfLength length: Int) {
    guard length > 0 else {
        self.init()
        return
    }

    let base = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    var randomString = ""
    for _ in 1...length {
        randomString.append(base.randomElement()!)
    }
    self = randomString
}

我做了一些改变，并使用这个实现

static func random(randomOfLength length: Int) -> String {
    guard length > 0 else { return "" }
    let base = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    var randomString = ""
    for _ in 1...length {
        guard let randomCharacter = base.randomElement() else { continue }
        randomString.append(randomCharacter)
    }
    return randomString
}

你也可以这样使用它:

extension String {

    static func random(length: Int = 20) -> String {

        let base = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
        var randomString: String = ""

        for _ in 0..<length {

            let randomValue = arc4random_uniform(UInt32(base.characters.count))
            randomString += "\(base[base.startIndex.advancedBy(Int(randomValue))])"
        }

        return randomString
    }
}

简单的用法:

let randomString = String.random()

Swift 3语法:

extension String {

    static func random(length: Int = 20) -> String {
        let base = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
        var randomString: String = ""

        for _ in 0..<length {
            let randomValue = arc4random_uniform(UInt32(base.characters.count))
            randomString += "\(base[base.index(base.startIndex, offsetBy: Int(randomValue))])"
        }
        return randomString
    }
}

Swift 4语法:

extension String {

    static func random(length: Int = 20) -> String {
        let base = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
        var randomString: String = ""

        for _ in 0..<length {
            let randomValue = arc4random_uniform(UInt32(base.count))
            randomString += "\(base[base.index(base.startIndex, offsetBy: Int(randomValue))])"
        }
        return randomString
    }
}

更新后的2019年。

在不寻常的情况下

性能很重要。

下面是一个非常清晰的缓存函数:

func randomNameString(length: Int = 7)->String{
    
    enum s {
        static let c = Array("abcdefghjklmnpqrstuvwxyz12345789")
        static let k = UInt32(c.count)
    }
    
    var result = [Character](repeating: "-", count: length)
    
    for i in 0..<length {
        let r = Int(arc4random_uniform(s.k))
        result[i] = s.c[r]
    }
    
    return String(result)
}

这适用于当您有一个固定的、已知的字符集时。

方便的提示:

注意，“abcdefghjklmnpqrstuvwxyz12345789”避免了“坏”字符

没有0,o, o, i等等…人类经常混淆的字符。

这通常用于预订代码和人类客户将使用的类似代码。

我对这个问题的更快速的回答是:

func randomAlphanumericString(length: Int) -> String {

    let letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".characters
    let lettersLength = UInt32(letters.count)

    let randomCharacters = (0..<length).map { i -> String in
        let offset = Int(arc4random_uniform(lettersLength))
        let c = letters[letters.startIndex.advancedBy(offset)]
        return String(c)
    }

    return randomCharacters.joinWithSeparator("")
}

如果您只需要一个唯一标识符UUID()。uuidString可以满足您的需求。

斯威夫特5.6

此函数生成一个以36为基数的10位数字，然后将其作为字母数字字符串返回。

func randomCode(length: Int) -> String {
    let radix = 36 // = 10 digits + 26 letters
    let number = Int.random(in: 0..<(pow(radix, length)))
    return String(number, radix: radix, uppercase: true)
}

或者如果你不希望代码以“0”开头:

func randomCode(length: Int) -> String {
    let radix = 36 // = 10 digits + 26 letters
    let range = (pow(radix, length)/2)..<(pow(radix, length))
    let number = Int.random(in: range)
    return String(number, radix: radix, uppercase: true)
}