マイナンバー チェックデジット

gistfile1.swift

extension String {
  func isValidMyNumber() -> Bool {
    enum Error: ErrorType {
      case NonNumber
    }
    let numbers: [Int]
    do {
      numbers = try self.characters.map { (char) -> Int in
        guard let value = Int(String(char)) else {
          throw Error.NonNumber
        }
        return value
      }
    } catch {
      return false
    }
    guard numbers.count == 12 else {
      return false
    }
    let sum = (1...11).reduce(0) { (current, index) -> Int in
      let p = numbers[11 - index]
      let q: Int
      if 1...6 ~= index {
        q = index + 1
      } else {
        q = index - 5
      }
      return current + p * q
    }
    return 11 - sum % 11 == numbers[11]
  }
}

let matrix = [
  "123456789010": false,
  "123456789011": false,
  "123456789012": false,
  "123456789013": false,
  "123456789014": false,
  "123456789015": false,
  "123456789016": false,
  "123456789017": false,
  "123456789018": true,
  "123456789019": false,
  "023456789013": true,
  "02345678901X": false,
  "02345678901XX": false,
  "023456789013X": false,
]

matrix.forEach { (string, result) -> () in
  assert(string.isValidMyNumber() == result)
}