Validate Iranian national code in Swift 4 - کنترل صحت کد ملی ایران

ValidateIranianNationalCode.swift

    func validate(input: String) -> Bool {
        
        let digits = input.map { Int(String($0)) }
        
        guard digits.count == 10 && digits.count == input.count else {
            return false
        }
        
        let check = digits[9]!
        let remainder = digits.prefix(upTo: 9).enumerated().reduce(0) { 
          $0 + $1.element! * (10 - $1.offset) 
        } % 11
        
        return remainder < 2 ? check == remainder : check + remainder == 11
        
    }