Rails Validation that use validates a string with a regex?

Question

I have a Message.uuid field which I want to add validations for which include:

Supported:

A-Z, a-z, 0-9
dashes in the middle but never starting or ending in a dash.
At least 5, no more than 500 characters

What is the best way in rails to write a model validation for these rules?

Thanks

UPDATE:

  validates :uuid,
    :length => { :within => 5..500 },
    :format => { :with => /[A-Za-z\d][-A-Za-z\d]{3,498}[A-Za-z\d]/ }

With a valid UUID this is failing

You need to anchor your regular expression between ^ and $, or something like "@%#@#$AAAAA@#%@#$" will pass. — user229044
– user229044 ♦, Commented Aug 31, 2011 at 19:21
You should also limit the scope of your format validator; you currently attempting to validate length twice, and a UUID like AAA will cause two errors: one about the length, and one about the format. You probably only want it to cause a length error. — user229044
– user229044 ♦, Commented Aug 31, 2011 at 19:24

user229044 · Accepted Answer · 2011-08-31 19:23:59Z

7

I'd leave the length validation up to a validates_length_of validator, so that you get more specific error messages. This will do two things for you: Simplify the regex used with your validates_format_of validator, and provide a length-specific error message when the uuid is too short/long rather than showing the length error as a "format" error.

Try the following:

validates_length_of :uuid, :within => 5..500
validates_format_of :uuid, :with => /^[a-z0-9]+[-a-z0-9]*[a-z0-9]+$/i

You can combine the two validations into a single validates with Rails 3:

validates :uuid,
    :length => { :within => 5..500 },
    :format => { :with => /^[a-z0-9][-a-z0-9]*[a-z0-9]$/i }

edited Aug 31, 2011 at 19:23

answered Aug 31, 2011 at 18:22

user229044♦

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5 Comments

Benoit Garret Over a year ago

Aren't you missing the caps here?

user229044 Over a year ago

@Benoit I was, briefly, but remembered the /i on the regex which ignores case.

AnApprentice Over a year ago

Just tried this but it doesn't seem to be working, it keeps redirecting. I've pasted the code I'm using above. Thoughts?

AnApprentice Over a year ago

Even just using the validates_length_of with a input of 123412 is causing a redirect

user229044 Over a year ago

@ColdTree Validators don't cause redirects. Models don't even cause redirects. Whatever problem your encountering, it has nothing to do with your models. Try running rails console and creating a Message with an invalid UUID, and checking which errors it has.

Community · Accepted Answer · 2017-05-23 12:12:06Z

2

Use:

validates :uuid, :format => {:with => /my regexp/}

As for the regexp, you've already asked for it in another question.

edited May 23, 2017 at 12:12

CommunityBot

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answered Aug 31, 2011 at 18:22

Benoit Garret

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