生成随机字符串后的奇怪返回值（Swift 3）

Question

我创建了一个生成并返回字母和数字的随机字符串的方法，但由于某种原因，我只得到一个带数字的字符串，字符串的长度不接近我要求的字符串是。返回的一些字符串示例：“478388299949939566”（插入18作为长度），“3772919388584334”（插入9作为长度），“2293010089409293945”（插入6作为长度）。任何人都能看到我在这里缺少的东西吗？

func generateRandomStringWithLength(length:Int) -> String {

    let randomString:NSMutableString = NSMutableString(capacity: length)

    let letters:NSMutableString = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

    for index in 0...length {

        let randomIndex:Int = Int(arc4random_uniform(UInt32(62)))
        randomString.append("\(letters.character(at: randomIndex))")

    }

    return String(randomString)
}

Answer 1

你的问题在这里：

letters.character(at: randomIndex)

它的函数返回给定UTF-16代码单元索引处的字符，而不仅仅是字符

这是我的版本，我想它更快。

func generateRandomStringWithLength(length: Int) -> String {

    var randomString = ""
    let letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

    for _ in 1...length {
        let randomIndex  = Int(arc4random_uniform(UInt32(letters.characters.count)))
        let a = letters.index(letters.startIndex, offsetBy: randomIndex)
        randomString +=  String(letters[a])
    }

    return randomString
}

generateRandomStringWithLength(length: 5)

Answer 2

使用此：

func generateRandomStringWithLength(length:Int) -> String {

        let randomString:NSMutableString = NSMutableString(capacity: length)

        let letters:NSMutableString = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

        var i: Int = 0

        while i < length {

            let randomIndex:Int = Int(arc4random_uniform(UInt32(letters.length)))
            randomString.appendString("\(Character( UnicodeScalar( letters.characterAtIndex(randomIndex))))")
            i += 1
        }

        return String(randomString)
    }

调用generateRandomStringWithLength方法：

print(generateRandomStringWithLength(5))

print(generateRandomStringWithLength(10))

print(generateRandomStringWithLength(20))

print(generateRandomStringWithLength(7))

print(generateRandomStringWithLength(14))

样本输出：

GIrqb
nWmieQRVdk
r0It9V1xkGFRa2HVwtCw
RLIRuVI
nXnFGV2LQ3CjbD