I was looking at implementing a luhn and credit card type check the other day in java and I noticed that there seems to be a lack of code for doing this in ruby. So I figured I would put something together for doing the checks in ruby.
The following function will do a luhn check for a given number (any number not just credit card numbers). The luhn algorithm is fairly simple, if you want to learn more about it check here.
def luhnCheck(ccNumber)
ccNumber = ccNumber.gsub(/\D/, '')
cardLength = ccNumber.length
parity = cardLength % 2
sum = 0
for i in 0...cardLength
digit = ccNumber[i] - 48
if i % 2 == parity
digit = digit * 2
end
if digit > 9
digit = digit - 9
end
sum = sum + digit
end
return (sum % 10) == 0
end
Before running the luhn check you may want to verify that you have a valid card type or at least one you want to accept. The following function will do that based on the current bin ranges for the differenct companies as of today (for more on this see the following: credit card number information and BIN range information). N.B. Bin ranges change from time to time so this will become dated. It should be easy enough to find the updated ranges.
def ccTypeCheck(ccNumber)
ccNumber = ccNumber.gsub(/\D/, '')
case ccNumber
when /^3[47]\d{13}$/ then return "AMEX"
when /^4\d{12}(\d{3})?$/ then return "VISA"
when /^5\d{15}|36\d{14}$/ then return "MC"
when /^6011\d{12}|650\d{13}$/ then return "DISC"
when /^3(0[0-5]|8[0-1])\d{11}$/ then return "DINERS"
when /^(39\d{12})|(389\d{11})$/ then return "CB"
when /^3\d{15}|1800\d{11}|2131\d{11}$/ then return "JCB"
else return "NA"
end
end
1
A Ruby method without a coroutine? I just can’t stand it…
Seriously though, I tried to give this one a bit more of the Ruby sass…so far it matches the results of the original.
Of course, it is a judgement call which is easier to read and to follow.
I think my only real claim to an improvement is that now the core of the algorithm is normalized to accept an Enumerable of numeric values; slightly more reusable maybe someday in some context?
2
Just a small point, that regexp only removes capital Ds, it should really be /\D/ instead.
3
In addition to wrighty’s comment:
Another small point, but in all regexps in the ccTypeCheck() method, the lowercase “d”s should all really be “\d” (ie. the digit character class for Ruby regexps)
(I guess the ruby source code on this page gets mangled when it is rendered as HTML by the blogging software, or some such thing, and the backslashes removed in the process)
4
Sir,
How can the extraction of name on a credit card be made? your urgent response Sir. Thanks.
5
Here is an even shorter version. It relies on the fact that the check digit (rightmost) is always considered odd. So we reverse the number and toggle the odd flag on each accumulation iteration.
def valid_luhn?(num)
num = num.to_s.reverse.split(//).map { |d| d.to_i }
odd = false
num.inject(0) { |memo, i|
memo + ((odd = !odd) ? i : (i*2 > 9 ? i*2 - 9 : i*2))
} % 10 == 0
end
6
here’s my version:
def check_digits? num
odd = true
num.to_s.gsub(/\D/,'').reverse.split('').map(&:to_i).collect { |d|
d *= 2 if odd = !odd
d > 9 ? d - 9 : d
}.sum % 10 == 0
end