module Sjekksum::UPC

Module for calculation and validation of UPC (Universal Product Code) checksums

@see en.wikipedia.org/wiki/Universal_Product_Code#Check_digits Universal Product Code

It's like Luhn but multiplies by 3 instead of 2. Also it must allow validation of numbers with leading zeros.

Public Instance Methods

checksum(number)
Alias for: of
convert(number) click to toggle source

Transforms a number by appending the UPC checksum digit

It will preserve type (Integer/String) and therefore leading zeros.

@example

Sjekksum::UPC.convert("03600024145") #=> "036000241457"

@param number [Integer, String] number without a checksum

@return [Integer, String] final number including the checksum

# File lib/sjekksum/upc.rb, line 62
def convert number
  raise_on_type_mismatch number
  typed_conversion number
end
Also aliased as: transform
is_valid?(number)
Alias for: valid?
of(number) click to toggle source

Calculates UPC checksum

@example

Sjekksum::UPC.of("03600024145") #=> 7

@param number [Integer, String] number for which the checksum should be calculated

@return [Integer] calculated checksum

# File lib/sjekksum/upc.rb, line 23
def of number
  raise_on_type_mismatch number
  digits = convert_number_to_digits(number)

  sum    = digits.map.with_index do |digit, idx|
    idx.even? ? (digit * 3) : digit
  end.reduce(&:+)

  (10 - sum % 10) % 10
end
Also aliased as: checksum
transform(number)
Alias for: convert
valid?(number) click to toggle source

UPC validation of provided number

@example

Sjekksum::UPC.valid?("036000241457") #=> true

@param number [Integer, String] number with included checksum

@return [Boolean]

# File lib/sjekksum/upc.rb, line 44
def valid? number
  raise_on_type_mismatch number
  num, check = split_number(number)
  self.of(num) == check
end
Also aliased as: is_valid?