我如何在Swift中生成一个随机的字母数字字符串?
当前回答
如果你的随机字符串应该是安全随机的,使用这个:
import Foundation
import Security
// ...
private static func createAlphaNumericRandomString(length: Int) -> String? {
// create random numbers from 0 to 63
// use random numbers as index for accessing characters from the symbols string
// this limit is chosen because it is close to the number of possible symbols A-Z, a-z, 0-9
// so the error rate for invalid indices is low
let randomNumberModulo: UInt8 = 64
// indices greater than the length of the symbols string are invalid
// invalid indices are skipped
let symbols = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
var alphaNumericRandomString = ""
let maximumIndex = symbols.count - 1
while alphaNumericRandomString.count != length {
let bytesCount = 1
var randomByte: UInt8 = 0
guard errSecSuccess == SecRandomCopyBytes(kSecRandomDefault, bytesCount, &randomByte) else {
return nil
}
let randomIndex = randomByte % randomNumberModulo
// check if index exceeds symbols string length, then skip
guard randomIndex <= maximumIndex else { continue }
let symbolIndex = symbols.index(symbols.startIndex, offsetBy: Int(randomIndex))
alphaNumericRandomString.append(symbols[symbolIndex])
}
return alphaNumericRandomString
}
其他回答
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
}
}
针对Swift 3.0
func randomString(_ length: Int) -> String {
let letters : NSString = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
let len = UInt32(letters.length)
var randomString = ""
for _ in 0 ..< length {
let rand = arc4random_uniform(len)
var nextChar = letters.character(at: Int(rand))
randomString += NSString(characters: &nextChar, length: 1) as String
}
return randomString
}
一种避免输入整套字符的方法:
func randomAlphanumericString(length: Int) -> String {
enum Statics {
static let scalars = [UnicodeScalar("a").value...UnicodeScalar("z").value,
UnicodeScalar("A").value...UnicodeScalar("Z").value,
UnicodeScalar("0").value...UnicodeScalar("9").value].joined()
static let characters = scalars.map { Character(UnicodeScalar($0)!) }
}
let result = (0..<length).map { _ in Statics.characters.randomElement()! }
return String(result)
}
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)
}
免费循环,尽管它被限制在43个字符。如果你需要更多,可以修改。与单独使用UUID相比,这种方法有两个优点:
“更大的熵”使用小写字母,因为UUID()只生成大写字母 UUID最大长度为36个字符(包括4个连字符),不包含连字符的长度为32个字符。你应该需要更长的东西,或不希望连字符包括,使用base64EncodedString处理这个
此外,该函数使用UInt来避免负数。
func generateRandom(size: UInt) -> String {
let prefixSize = Int(min(size, 43))
let uuidString = UUID().uuidString.replacingOccurrences(of: "-", with: "")
return String(Data(uuidString.utf8)
.base64EncodedString()
.replacingOccurrences(of: "=", with: "")
.prefix(prefixSize))
}
在循环中调用它来检查输出:
for _ in 0...10 {
print(generateRandom(size: 32))
}
生产:
Nzk3NjgzMTdBQ0FBNDFCNzk2MDRENzZF
MUI5RURDQzE1RTdCNDA3RDg2MTI4QkQx
M0I3MjJBRjVFRTYyNDFCNkI5OUM1RUVC
RDA1RDZGQ0IzQjI1NDdGREI3NDgxM0Mx
NjcyNUQyOThCNzhCNEVFQTk1RTQ3NTIy
MDkwRTQ0RjFENUFGNEFDOTgyQTUxODI0
RDU2OTNBOUJGMDE4NDhEODlCNEQ1NjZG
RjM2MTUxRjM4RkY3NDU2OUFDOTI0Nzkz
QzUwOTE1N0U1RDVENDE4OEE5NTM2Rjcy
Nzk4QkMxNUJEMjYwNDJDQjhBQkY5QkY5
ODhFNjU0MDVEMUI2NEI5QUIyNjNCNkVF
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