Create regular expression in ruby on rails for validate username

Question

I need create a regular expression in ruby on rails for validate the user name following this rules:

 1)- The user name accept only lowercase letters, numbers,dashes and underscores
 2)- The first character must be a lowercase letter
 3)- The username have as minimum 6 characters and 30 characters as maximun

I thought some like this, but I'm not very sure

  /^ ([a-z][a-z\_-0-9]+){6,30}  $/

Answer 1

I'd suggest the following:

/^[a-z][a-z\-0-9_]{5,29}$/

I'll break it down:

• ^[az] - the sequence starts with ( ^ ) a lowercase character
• [az\\-0-9_] - any of the chars in that group
• {5,29} - between 5 and 29 (30 max, minus the one at the start of the sequence) of the previous set of chars
• $ the end of the sequence

You mentioned character classes - sure, you can use them. I typically don't because they're not as portable (someone may chime in and prove me wrong here) and I don't think they're as easy to understand, simply because I tend to forget which ones are which. YMMV