The logic to validate Iranian National Code

IranianNationalCodeValidator.swift

func validateNationalCode(_ code: String) -> Bool {

    let stringCode = code.trimmingCharacters(in: CharacterSet.decimalDigits.inverted)
    if code.allSatisfy({ $0 == code.first }) { return false }

    guard stringCode.count == 10 else { return false }

    var convertedCode = code.compactMap { Int(String($0)) }
    guard convertedCode.count == 10 else { return false }

    let lastDigit = convertedCode.removeLast()

    let prefixSum = convertedCode.enumerated().reduce(0) { $0 + ($1.element * (code.count - $1.offset)) }

    let checksum = prefixSum - (prefixSum / 11) * 11

    if [0, 1].contains(lastDigit) && lastDigit == checksum { return true }
    if checksum > 1 && lastDigit == abs(checksum - 11) { return true }
    return false
}