マイナンバーのチェックデジットをSwiftで計算する ref: http://qiita.com/su_k/items/4b442e3094fdea031065

Failureを返すパターン

enum ValidationResult {
    case Success
    case Failure(ValidationErrorType)
}

enum ValidationErrorType: ErrorType {
    case WrongLength(Int) // マイナンバーの桁数(文字数)が不正の場合
    case NotANumber // 数字以外が含まれている場合
    case InvalidNumber // 検査して不正なマイナンバーだった場合
}

// 便宜上関数名末尾に2をつけています。
func validateMyNumber2(numstr: String) -> ValidationResult {

    let length = numstr.utf8.count
    if length != 12 {
        return ValidationResult.Failure(.WrongLength(length))
    }

    let exp = try! NSRegularExpression(pattern: "^[0-9]+$", options: [])
    if exp.matchesInString(numstr, options: [], range: NSMakeRange(0, length)).count == 0 {
        return ValidationResult.Failure(.NotANumber)
    }

    var characters = numstr.characters.map{ String($0) }
    let checkDigit = Int(characters.removeLast())!

    var pq = 0

    for (index, num) in characters.reverse().enumerate() {
        let n = index + 1
        let p = Int(num)!
        let q = (n >= 7) ? n - 5 : n + 1
        pq += p * q
    }

    let remainder = pq % 11
    let valid = (remainder <= 1) ? (checkDigit == 0) : (checkDigit == (11 - remainder))
    return valid ? ValidationResult.Success : ValidationResult.Failure(.InvalidNumber)
}

falseを返すパターン

func validateMyNumber(numstr: String) -> Bool {

    // 桁数チェック
    let length = numstr.utf8.count
    if length != 12 {
        return false
    }

    // 正規表現を使って数字のみかどうかチェック
    let exp = try! NSRegularExpression(pattern: "^[0-9]+$", options: [])
    if exp.matchesInString(numstr, options: [], range: NSMakeRange(0, length)).count == 0 {
        return false
    }

    // 扱いやすいように一旦Stringを１文字ずつ分割
    var characters = numstr.characters.map{ String($0) }
    // チェックデジットをcharactersからpop
    // pop後はcharactersの中身は12->11個になります。
    let checkDigit = Int(characters.removeLast())!

    // 検査用数字の計算
    var pq = 0

    for (index, num) in characters.reverse().enumerate() {
        let n = index + 1
        let p = Int(num)!
        let q = (n >= 7) ? n - 5 : n + 1
        pq += p * q
    }

    // 検査
    let remainder = pq % 11
    return (remainder <= 1) ? (checkDigit == 0) : (checkDigit == (11 - remainder))
}

file4.swift

// 上記ソースの後に貼っても動くように便宜上"__"をつけておきます。
func __validateMyNumber(numstr: String) throws -> Bool {

    let length = numstr.utf8.count
    if length != 12 {
        throw ValidationErrorType.WrongLength(length)
    }

    let exp = try! NSRegularExpression(pattern: "^[0-9]+$", options: [])
    if exp.matchesInString(numstr, options: [], range: NSMakeRange(0, length)).count == 0 {
        throw ValidationErrorType.NotANumber
    }

    var characters = numstr.characters.map{ String($0) }
    let checkDigit = Int(characters.removeLast())!

    var pq = 0

    for (index, num) in characters.reverse().enumerate() {
        let n = index + 1
        let p = Int(num)!
        let q = (n >= 7) ? n - 5 : n + 1
        pq += p * q
    }

    let remainder = pq % 11
    return (remainder <= 1) ? (checkDigit == 0) : (checkDigit == (11 - remainder))
}

func tryValidation(numstr: String) {
    do {
        let valid = try __validateMyNumber(numstr)
        print("\(numstr) is",(valid ? "valid" : "invalid"))
    } catch ValidationErrorType.WrongLength(let length) {
        print("\(numstr) is wrong length: \(length)")
    } catch ValidationErrorType.NotANumber {
        print("\(numstr) is not a number")
    } catch {
        print("unknown error occurred")
    }
}

tryValidation("123456789012") // => "123456789012 is invalid\n"

結果

validateMyNumber("1234567890123") // => false
validateMyNumber("１２３４５６７８９０１０") // => false
validateMyNumber("A23456789010") // => false
validateMyNumber("123456789010") // => false
validateMyNumber("123456789011") // => false
validateMyNumber("123456789012") // => false
validateMyNumber("123456789013") // => false
validateMyNumber("123456789014") // => false
validateMyNumber("123456789015") // => false
validateMyNumber("123456789016") // => false
validateMyNumber("123456789017") // => false
validateMyNumber("123456789018") // => true
validateMyNumber("123456789019") // => false
validateMyNumber("023456789013") // => true

結果2

validateMyNumber2("1234567890123") // -> Failure(ValidationErrorType.WrongLength(13))
validateMyNumber2("１２３４５６７８９０１０") // -> Failure(ValidationErrorType.WrongLength(36))
validateMyNumber2("A23456789010") // => Failure(ValidationErrorType.NotANumber)
validateMyNumber2("123456789010") // => Failure(ValidationErrorType.InvalidNumber)
validateMyNumber2("123456789011") // => Failure(ValidationErrorType.InvalidNumber)
validateMyNumber2("123456789012") // => Failure(ValidationErrorType.InvalidNumber)
validateMyNumber2("123456789013") // => Failure(ValidationErrorType.InvalidNumber)
validateMyNumber2("123456789014") // => Failure(ValidationErrorType.InvalidNumber)
validateMyNumber2("123456789015") // => Failure(ValidationErrorType.InvalidNumber)
validateMyNumber2("123456789016") // => Failure(ValidationErrorType.InvalidNumber)
validateMyNumber2("123456789017") // => Failure(ValidationErrorType.InvalidNumber)
validateMyNumber2("123456789018") // => Success
validateMyNumber2("123456789019") // => Failure(ValidationErrorType.InvalidNumber)
validateMyNumber2("023456789013") // => Success