Question

I’m trying to create a Regex to check for 6-12 characters, one being a digit, the rest being any characters, no spaces. Can Regex do this? I’m trying to do this in objective-c and I’m not familiar with Regex at all. I’ve been reading a couple tutorials, but most are for matching simple cases of a number, or a set of numbers, but not exactly what i’m looking for. I can do it with methods, but I was wondering if it that would be too slow and I figured I could try learning something new.

asdfg1 == ok
asdfg 1 != ok
asdfgh != ok
123456 != ok
asdfasgdasgdasdfasdf != ok

Answer 1

It seems that you mean “letter” when you say “character”, right? And (thanks to burning_LEGION for pointing that out) there may be only one digit?

In that case, use

^(?=\D*\d\D*$)[^\W_]{6,12}$

Explanation:

^             # Start of string
(?=\D*\d\D*$) # Assert that there is exactly one digit in the string
[^\W_]        # Match a letter or digit (explanation below)
{6,12}        # 6-12 times
$             # End of string

[^\W_] might look a little odd. How does it work? Well, \w matches any letter, digit or underscore. \W matches anything that \w doesn’t match. So [^\W] (meaning “match any character that is not not alphanumeric/underscore”) is essentially the same as \w, but by adding _ to this character class, we can remove the underscore from the list of allowed characters.