Validating no spaces in field


I've never been much of a regex wrangler, and learning rails at the same time isn't helping.

I want to create a validation that fails if a user tries to create a username with spaces. But I can't seem to get the right validates_format_of regex going.

Can anyone help with this simple question?

Thanks! Andrew

validates_format_of :username, :with => /^\S+$/

but that's still probably too open for a username (it'll allow "u $ern4m3" for instance)

Most of the time, usernames are restricted to:

validates_format_of :username, :with => /^[a-zA-Z][a-z0-9A-Z]{2,10}$/

(usernames starting with a letter, followed by 2 or more letters or digits up to 10, min username length = 3, max username length = 11)

here are a few links that explain the syntax concisely: - -

Thank you so much, that did the trick perfectly!

And double thanks for teaching a man to fish. I think I might be able to write a simple regex of my own now!

Thanks again!!!


While I think that your regex is smokin’ hot, I do think you might be better served [at least on the error messages front] by two validations there:

validates_format_of :username, :with => /[1][a-z0-9A-Z]*$/, :message => “can only contain letters and numbers” # Or something

validates_length_of, :minimum => 2, :maximum => 10, :too_short => “must be at least 2 characters”, :too_long => “cannot be longer than 10 characters”

that way you’ll have separate error messages for each problem rather than having to lump them all in together. You way does work though. I’m just trying to offer a helpful hint.


  1. a-zA-Z ↩︎


I agree and my model already had a validates_length_of so I modified the proposed regex to eliminate the length check.

Discussing this with my partner we decided to allow numbers, letters, and underscore (_) so I am going to try the regex /^[a-zA-Z0-9_]*$/

We don't care if the first character is a letter, number, or underscore, only that these are the only characters allowed anywhere in the username. So "_username", "user_name", and "1user_name" should all be valid.

Think this should work? I don't have access to the site to test it until I get home tonight.

I had never noticed that validates_length_of supports two error messages, one for too short, and one for too long. I'll have to implement that in my code tonight as well.

Now if I could only find a non-ugly way to sort the error messages so they match the order of the form fields I'd be all set. :frowning:

It’s not [that] hard to roll your own version of error_messages_on. Something like

def error_messages_hacked(instance, *order) return if instance.errors.empty? dummy = do |attribute| “#{instance} #{ instance.errors_on(attribute)}” end.flatten

Do any HTML styling you want on dummy

which will be a collection of error message strings


<%= error_messages_hacked @user, :name, :email, :whatever -%>

That’s pretty not ugly, right?