# From string to field name

**URL:** <https://www.ruby-forum.com/t/from-string-to-field-name/188616>\
**Category:** Rails\
**Created:** [May 14, 2010, 8:26pm UTC](https://www.ruby-forum.com/t/from-string-to-field-name/188616 "2010-05-14T20:26:15Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![Viorel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/bcef8e/32.png) [@Viorel](https://www.ruby-forum.com/u/Viorel)\
**Post date:** [May 14, 2010, 8:26pm UTC](https://www.ruby-forum.com/t/from-string-to-field-name/188616/1 "2010-05-14T20:26:15Z")

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I have something like this:  
for xx in ‘01’…‘09’  
field\_name=‘field’+xx  
puts ModelName.field\_name  
end

My problem is that ModelName has no field named field\_name, it have  
fields like field01, field02,…,field09. So, how do I transform a  
string in a field name?

It might be a trivial solution, but I can’t find it. I would  
appreciate any help.

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**Author:** ![Viorel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/bcef8e/32.png) [@Viorel](https://www.ruby-forum.com/u/Viorel)\
**Post date:** [May 14, 2010, 8:35pm UTC](https://www.ruby-forum.com/t/from-string-to-field-name/188616/2 "2010-05-14T20:35:37Z")

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I am trying to access those fields

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**Author:** ![Viorel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/bcef8e/32.png) [@Viorel](https://www.ruby-forum.com/u/Viorel)\
**Post date:** [May 14, 2010, 8:28pm UTC](https://www.ruby-forum.com/t/from-string-to-field-name/188616/3 "2010-05-14T20:28:00Z")

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What exactly are you trying to do with this?

On Fri, May 14, 2010 at 2:24 PM, Viorel [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> It might be a trivial solution, but I can’t find it. I would  
> For more options, visit this group at  
> [http://groups.google.com/group/rubyonrails-talk?hl=en](http://groups.google.com/group/rubyonrails-talk?hl=en).

–

* * *

Joshua S. Martin

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<div class="post-metadata">

**Author:** ![Viorel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/bcef8e/32.png) [@Viorel](https://www.ruby-forum.com/u/Viorel)\
**Post date:** [May 14, 2010, 8:36pm UTC](https://www.ruby-forum.com/t/from-string-to-field-name/188616/4 "2010-05-14T20:36:47Z")

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On May 14, 9:26 pm, Joshua M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> What exactly are you trying to do with this?  
> I am trying to access these fields

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<div class="post-metadata">

**Author:** ![Viorel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/bcef8e/32.png) [@Viorel](https://www.ruby-forum.com/u/Viorel)\
**Post date:** [May 14, 2010, 8:42pm UTC](https://www.ruby-forum.com/t/from-string-to-field-name/188616/5 "2010-05-14T20:42:39Z")

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Thank you Michel! I works!

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<div class="post-metadata">

**Author:** ![Viorel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/bcef8e/32.png) [@Viorel](https://www.ruby-forum.com/u/Viorel)\
**Post date:** [May 14, 2010, 8:37pm UTC](https://www.ruby-forum.com/t/from-string-to-field-name/188616/6 "2010-05-14T20:37:58Z")

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On 14 May 2010 19:24, Viorel [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> My problem is that ModelName has no field named field\_name, it have  
> fields like field01, field02,…,field09. So, how do I transform a  
> string in a field name?

puts ModelName.send(field\_name)

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<div class="post-metadata">

**Author:** ![Viorel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/bcef8e/32.png) [@Viorel](https://www.ruby-forum.com/u/Viorel)\
**Post date:** [May 14, 2010, 9:11pm UTC](https://www.ruby-forum.com/t/from-string-to-field-name/188616/7 "2010-05-14T21:11:56Z")

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Or model\_name.read\_attribute(field\_name)

However if you multiple fields like that, it sounds like you need a  
has\_many relationship.

has\_many :field\_names

object.field\_names.each do |field\_mame|

# do something

end

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<div class="post-metadata">

**Author:** ![Viorel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/bcef8e/32.png) [@Viorel](https://www.ruby-forum.com/u/Viorel)\
**Post date:** [May 14, 2010, 9:23pm UTC](https://www.ruby-forum.com/t/from-string-to-field-name/188616/8 "2010-05-14T21:23:38Z")

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On May 14, 10:10 pm, David [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> > Great. Now normalize your database schema to get rid of those repeating  
> > fields.

You are absolutely right, both of you. It is not my schema, but I hope  
that your answers will persuade those responsible. Than you!

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<div class="post-metadata">

**Author:** ![Viorel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/bcef8e/32.png) [@Viorel](https://www.ruby-forum.com/u/Viorel)\
**Post date:** [May 14, 2010, 8:51pm UTC](https://www.ruby-forum.com/t/from-string-to-field-name/188616/9 "2010-05-14T20:51:33Z")

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[Please quote when replying]

Viorel wrote:

> Thank you Michel! I works!

Great. Now normalize your database schema to get rid of those repeating  
fields.

## Best,

Marnen Laibow-Koser  
[http://www.marnen.org](http://www.marnen.org)  
removed\_email\_address@domain.invalid