Module: Sjekksum::UPC

Extended by:
Shared, UPC
Included in:
UPC
Defined in:
lib/sjekksum/upc.rb

Overview

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

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

Instance Method Summary collapse

Instance Method Details

#convert(number) ⇒ Integer, String Also known as: transform

Transforms a number by appending the UPC checksum digit

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

Examples:

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

Parameters:

  • number (Integer, String)

    number without a checksum

Returns:

  • (Integer, String)

    final number including the checksum


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# File 'lib/sjekksum/upc.rb', line 62

def convert number
  raise_on_type_mismatch number
  typed_conversion number
end

#of(number) ⇒ Integer Also known as: checksum

Calculates UPC checksum

Examples:

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

Parameters:

  • number (Integer, String)

    number for which the checksum should be calculated

Returns:

  • (Integer)

    calculated checksum


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# 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

#valid?(number) ⇒ Boolean Also known as: is_valid?

UPC validation of provided number

Examples:

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

Parameters:

  • number (Integer, String)

    number with included checksum

Returns:

  • (Boolean)

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# 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