Vehicle Identification Number (VIN or chassis number) validation in Swift 3.0 with String extension

StringUtils.swift

//
//  Created by Rashid Ramazanov on 18/01/2017.
//  Converted from Java snippet in https://en.wikipedia.org/wiki/Vehicle_identification_number#Example_Code
//

import Foundation

extension String {
    
    var isValidChassisNo: Bool {
        return getCheckDigit(vin: self) == (self as NSString).character(at: 8)
    }
    
    private func transliterate(char: unichar) -> Int {
        return ("0123456789.ABCDEFGH..JKLMN.P.R..STUVWXYZ" as NSString).range(of: String(Character(UnicodeScalar(char)!))).location % 10
    }
    
    private func getCheckDigit(vin: String) -> unichar {
        let map: NSString = "0123456789X"
        let weights: NSString = "8765432X098765432"
        var sum = 0
        for (index, _) in vin.characters.enumerated() {
            sum += transliterate(char: (vin as NSString).character(at: index)) * map.range(of: String(Character(UnicodeScalar(weights.character(at: index))!))).location
        }
        return map.character(at: sum % 11)
    }
    
}