Simple regex check failing in a rails model

Question

I have a check of the following type

 validates :callback_handle, :format => { :with => /[_0-9a-zA-Z]+/ix }, :unless  => "callback.nil?"

I do not want any non 0-9, a-z A-Z characters to pass. So i set callback_handle to "!alksjda" (note ! at the begining). This test does not fail. What am I doing wrong?

I tried a few things on irb: This is what I got:

1.9.2-p320 :001 > a = "!askldjlad"
 => "!askldjlad" 
1.9.2-p320 :002 > a =~ /[_0-9a-zA-Z]+/ix
 => 1 
1.9.2-p320 :003 > a = "askldjlad"
 => "askldjlad" 
1.9.2-p320 :004 > a =~ /[_0-9a-zA-Z]+/ix
 => 0

I thought it would return false or nil on failure to find the match.

Can someone tell me what is wrong here in my understanding?

EDIT: I figured out that =~ will return position of a match. So the question becomes How do I not allow something that has any other character to not match?

jdl · Accepted Answer · 2012-12-21 18:41:11Z

3

Your regular expression is still able to match, because there is at least 1 character in your string that is alpha-numeric. If you want to make sure that the entire string matches then you should define the beginning and end of the match.

Old:

a =~ /[_0-9a-zA-Z]+/ix

This is saying "match at least one of these characters somewhere in a.

New:

a =~ /\A[_0-9a-zA-Z]+\z/ix

This is saying "start at the beginning of the string, then match at least 1 of only these characters, followed by the end of the string" in a.

edited Dec 21, 2012 at 18:41

answered Dec 21, 2012 at 18:23

jdl

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3 Comments

jdoe Over a year ago

Nope, this is saying about a line, not a string. "a\n!" =~ /^[_0-9a-zA-Z]+$/ix returns 0. You need to use \A+\z pair instead: /\A[_0-9a-zA-Z]+\z/ix.

Firas Dib Over a year ago

Whats with the x-modifier?

jdl Over a year ago

The x is doing nothing in this particular case. It was copied from the original question, and I didn't worry about it, because it's also not hurting anything.

Anthony Alberto · Accepted Answer · 2012-12-21 18:23:10Z

1

Your regex just asks that your string contains 1 or more valid characters ... this should fix it :

 validates :callback_handle, :format => { :with => /^[_0-9a-zA-Z]+$/ix }, :unless  => "callback.nil?"

answered Dec 21, 2012 at 18:23

Anthony Alberto

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1 Comment

jdoe Over a year ago

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