# %r regex matching is ignoring my leading zeros

**URL:** <https://www.ruby-forum.com/t/r-regex-matching-is-ignoring-my-leading-zeros/56288>\
**Category:** Ruby\
**Created:** [March 29, 2006, 11:54pm UTC](https://www.ruby-forum.com/t/r-regex-matching-is-ignoring-my-leading-zeros/56288 "2006-03-29T23:54:41Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![ennyaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/e5b9ba/32.png) [@ennyaa](https://www.ruby-forum.com/u/ennyaa)\
**Post date:** [March 29, 2006, 11:54pm UTC](https://www.ruby-forum.com/t/r-regex-matching-is-ignoring-my-leading-zeros/56288/1 "2006-03-29T23:54:41Z")

</div>

Hello,

I hope someone can help me or at least confirm that I’m not going  
insane.

I have a model in which I’m trying to validate information before it  
saves.  
One particular field is for and expiration date. The code in my model  
to do the validation looks like this:

validates\_format\_of :expiration,  
:with =\> %r{^[\d]{4,4}$},  
:message =\> “must be formatted (mmyy)”

The problem is if someone enter a date that starts with a zero like  
“0309” The validation somehow just doesn’t “see” the leading zero and  
keeps returning an error as though the user isn’t submitting it  
properly. I did verify that the controller is definetly sending all  
four digits in the post.

I tried different combinations like: r{^(0|1)[\d]{3}$} but no matter  
what I did the zero was ignored. I finally had to change it to look for  
3 or 4 digits just to make it work but that of course isn’t proper  
validation as my submissions must have 4 digits.

Can anyone help me? Am I going crazy here?

Thanks,  
Dara

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<div class="post-metadata">

**Author:** ![ennyaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/e5b9ba/32.png) [@ennyaa](https://www.ruby-forum.com/u/ennyaa)\
**Post date:** [March 30, 2006, 12:30am UTC](https://www.ruby-forum.com/t/r-regex-matching-is-ignoring-my-leading-zeros/56288/2 "2006-03-30T00:30:56Z")

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Dara Sanderson schrieb:

> validates\_format\_of :expiration,  
> I tried different combinations like: r{^(0|1)[\d]{3}$} but no matter  
> what I did the zero was ignored. I finally had to change it to look for  
> 3 or 4 digits just to make it work but that of course isn’t proper  
> validation as my submissions must have 4 digits.
> 
> Can anyone help me? Am I going crazy here?
> 
> Thanks,  
> Dara

i am not an expert in RE but don’t you think [\d]{4,4} should be  
\d{4,4}

inside a class [] . and i think \ lose their special meaning

hth, Daniel

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**Author:** ![ennyaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/e5b9ba/32.png) [@ennyaa](https://www.ruby-forum.com/u/ennyaa)\
**Post date:** [March 30, 2006, 12:39am UTC](https://www.ruby-forum.com/t/r-regex-matching-is-ignoring-my-leading-zeros/56288/3 "2006-03-30T00:39:58Z")

</div>

Hi –

On Thu, 30 Mar 2006, Dara Sanderson wrote:

> validates\_format\_of :expiration,  
> I tried different combinations like: r{^(0|1)[\d]{3}$} but no matter  
> what I did the zero was ignored. I finally had to change it to look for  
> 3 or 4 digits just to make it work but that of course isn’t proper  
> validation as my submissions must have 4 digits.
> 
> Can anyone help me? Am I going crazy here?

My guess is that somewhere along the line the month is being turned  
into an integer and back to a string, so that “03” becomes 3 and then  
“3”. I don’t know where, though.

David

–  
David A. Black (removed\_email\_address@domain.invalid)  
Ruby Power and Light, LLC ([http://www.rubypowerandlight.com](http://www.rubypowerandlight.com))

“Ruby for Rails” chapters now available  
from Manning Early Access Program! [Ruby for Rails](http://www.manning.com/books/black)

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<div class="post-metadata">

**Author:** ![ennyaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/e5b9ba/32.png) [@ennyaa](https://www.ruby-forum.com/u/ennyaa)\
**Post date:** [March 30, 2006, 12:39am UTC](https://www.ruby-forum.com/t/r-regex-matching-is-ignoring-my-leading-zeros/56288/4 "2006-03-30T00:39:59Z")

</div>

Dara Sanderson ha scritto:

> validates\_format\_of :expiration,  
> :with =\> %r{^[\d]{4,4}$},  
> :message =\> “must be formatted (mmyy)”
> 
> The problem is if someone enter a date that starts with a zero like  
> “0309” The validation somehow just doesn’t “see” the leading zero and  
> keeps returning an error as though the user isn’t submitting it  
> properly. I did verify that the controller is definetly sending all  
> four digits in the post.

I think I’d write the Regexp as:  
%r{^\d{4}$}

Anyway, you one seem to work as expected on my box in irb:  
irb(main):001:0\> x=/^[\d]{4,4}$/  
=\> /^[\d]{4,4}$/  
irb(main):002:0\> x2=%r|^[\d]{4,4}$|  
=\> /^[\d]{4,4}$/  
irb(main):003:0\> x.match “0102”  
=\> #MatchData:0x2c0b300  
irb(main):004:0\> x2.match “0102”  
=\> #MatchData:0x2c08fa8

and in rails:  
$cat app\models\foo.rb  
class Foo \< ActiveRecord::Base  
validates\_format\_of :bar, :with=\>%r{^\d{4}$}  
end

> > f=Foo.new  
> > =\> #\<Foo:0x39658e8 @new\_record=true, @attributes={“bar”=\>""}\>
> 
> > f.bar =“0123”  
> > =\> “0123”
> 
> > f.save  
> > =\> true
> 
> > f.bar =“012”  
> > =\> “012”
> 
> > f.save  
> > =\> false

what version of ruby are you running?  
Maybe it could have been some damn pesky problem like not having  
reloaded the model (this happened to me many times 🙂 ?

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<div class="post-metadata">

**Author:** ![ennyaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/e5b9ba/32.png) [@ennyaa](https://www.ruby-forum.com/u/ennyaa)\
**Post date:** [March 30, 2006, 3:10am UTC](https://www.ruby-forum.com/t/r-regex-matching-is-ignoring-my-leading-zeros/56288/5 "2006-03-30T03:10:59Z")

</div>

First of all, thanks guys for trying to help.

I changed my model validation to remove the brackets from around the \d.  
Still no dice.

When I tried it irb as Gabriele did it worked fine though. Just doesn’t  
want to work on the actual form I’m using.

I’m afraid I dno’t know how to test rails as you have here:

> and in rails:  
> $cat app\models\foo.rb  
> class Foo \< ActiveRecord::Base  
> validates\_format\_of :bar, :with=\>%r{^\d{4}$}  
> end
> 
> > > f=Foo.new  
> > > =\> #\<Foo:0x39658e8 @new\_record=true, @attributes={“bar”=\>""}\>
> > 
> > > f.bar =“0123”  
> > > =\> “0123”
> > 
> > > f.save  
> > > =\> true
> > 
> > > f.bar =“012”  
> > > =\> “012”
> > 
> > > f.save  
> > > =\> false
> 
> what version of ruby are you running?  
> Maybe it could have been some damn pesky problem like not having  
> reloaded the model (this happened to me many times 🙂 ?

I’m hosted on Dreamhost so they’re on version 1.8.2 of ruby.

Maybe it does have something to do with conversion to a string. Maybe  
I’ll try and manipulate it in my controller before saving.

Any other suggestions?

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**Author:** ![ennyaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/e5b9ba/32.png) [@ennyaa](https://www.ruby-forum.com/u/ennyaa)\
**Post date:** [March 30, 2006, 12:14pm UTC](https://www.ruby-forum.com/t/r-regex-matching-is-ignoring-my-leading-zeros/56288/6 "2006-03-30T12:14:35Z")

</div>

Dara Sanderson ha scritto:

> First of all, thanks guys for trying to help.
> 
> I changed my model validation to remove the brackets from around the \d.  
> Still no dice.
> 
> When I tried it irb as Gabriele did it worked fine though. Just doesn’t  
> want to work on the actual form I’m using.
> 
> I’m afraid I dno’t know how to test rails as you have here:

this is just the the script/console thing in rails

> Any other suggestions?  
> It seem that the problem is hitting before the validation against the  
> regex is actually called, the string is mangled somewhere.  
> Maybe you can try defining your own validation method and checking that  
> the value is the expected one, or if maybe it is truncated as david  
> black suggested.