How to apply incrementing numbers from strings (invoice numbers)

Question

I am trying to implement incrementing invoice numbers on my current application, however I am confused as to how to go about it as the applications invoices are a string.

Currently the invoice numbers look like this: Q20140001 and they are supposed to increase by 1 for each new invoice (so the next invoice number would be Q20140002 ). All I would like to do is split the string ( in to Q and 20140001 ). Then I would like to have the 20140001 number increment to 20140002 .

My guess is that every time I want to create a new number, I check the last invoice number that was stored on the database, parse it into a string and an integer, take the integer and increment it by 1, and then add the Q back on to it.

I'm not sure if my approach is correct, though.

Answer 1

Did you tried using the String#succ method?

IRB session:

2.1.2 :001 > 'Q20140001'.succ
 => "Q20140002"
2.1.2 :002 >

One thing you must keep in mind is, that after 99999999 invoices, the result may not be what you want:

2.1.2 :002 > 'Q99999999'.succ
 => "R00000000"
2.1.2 :003 >

Q will be incremented to the next ASCII position R , resulting in R00000000 . One possible solution is to fill the invoice number with enough zeros, something like: Q00000000020140001 or leave the things as they are, which may be better in the long run.