# Can an hidden\_field changed be detected by observe\_form?

**URL:** <https://www.ruby-forum.com/t/can-an-hidden-field-changed-be-detected-by-observe-form/104972>\
**Category:** Rails\
**Created:** [May 24, 2007, 2:03pm UTC](https://www.ruby-forum.com/t/can-an-hidden-field-changed-be-detected-by-observe-form/104972 "2007-05-24T14:03:11Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![kadoudal](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/f0a364/32.png) [@kadoudal](https://www.ruby-forum.com/u/kadoudal)\
**Post date:** [May 24, 2007, 2:03pm UTC](https://www.ruby-forum.com/t/can-an-hidden-field-changed-be-detected-by-observe-form/104972/1 "2007-05-24T14:03:11Z")

</div>

in a view, I am changing programmatically an hidden field ‘category\_id’  
(simulating a click)

- \<%= link\_to\_function("Baby-sitting", nil, :class =\> "enfants") do |page| page \<

…  
\<%= hidden\_field\_tag :category\_id, @category\_id -%\>

I try to submit the form whenever this field (or other standard input  
field…) is changed

\<%= observe\_form(‘prop\_search\_form’,  
:loading =\> “Element.show(‘search\_spinner’);  
Form.disable(‘prop\_search\_form’);”,  
:complete =\> “Element.hide(‘search\_spinner’);  
Form.enable(‘prop\_search\_form’);”,  
:update =\> {}, :url =\> { :controller =\> ‘proposal’, :action =\> ‘list’ })  
%\>

any field is correctly detected but not this hidden field… is it wrong  
?  
I also tried to put this value in a readonly text field… same  
problem… change event is not detected

thanks for your help