# Observe\_field on multiple select box

**URL:** <https://www.ruby-forum.com/t/observe-field-on-multiple-select-box/175596>\
**Category:** Rails\
**Created:** [September 16, 2009, 8:13am UTC](https://www.ruby-forum.com/t/observe-field-on-multiple-select-box/175596 "2009-09-16T08:13:58Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![salil](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c89c15/32.png) [@salil](https://www.ruby-forum.com/u/salil)\
**Post date:** [September 16, 2009, 8:13am UTC](https://www.ruby-forum.com/t/observe-field-on-multiple-select-box/175596/1 "2009-09-16T08:13:58Z")

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Hi All,

I want to use observe\_field on multiple select box.  
following is my code

\<%= select\_tag ‘usa[states][]’,  
options\_from\_collection\_for\_select(state, :state, :state, nil),  
:multiple =\> true, :class=\>“multi\_select” %\>  
\<%= observe\_field :usa\_states\_ , :url =\>{:controller=\>“logins”,:action  
=\>‘multi\_select\_city’, :id=\>‘1’}, :update=\> ‘deliverable\_city’ , :with  
=\> “’  
state=’+document.getElementById(‘usa\_states\_’).value+’&type=restaurant’”,  
:on=\>‘click’ %\>

I want to select the city of the different State i selected through  
multiple select box.  
My problem is that i get only one value of a state when i click the  
multiple states i don’t where i’m goin wrong.  
Is it possible to use observe\_field on multiple select box?

Thanks & Regards,

Salil G.

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<div class="post-metadata">

**Author:** ![salil](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c89c15/32.png) [@salil](https://www.ruby-forum.com/u/salil)\
**Post date:** [September 16, 2009, 1:44pm UTC](https://www.ruby-forum.com/t/observe-field-on-multiple-select-box/175596/2 "2009-09-16T13:44:13Z")

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$(‘usa\_states\_’).value will return the first selected item’s value.  
It doesn’t matter if it is a multiple select. Change your UI a bit.

On Sep 16, 11:13 am, Salil G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)

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<div class="post-metadata">

**Author:** ![salil](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c89c15/32.png) [@salil](https://www.ruby-forum.com/u/salil)\
**Post date:** [September 17, 2009, 3:56pm UTC](https://www.ruby-forum.com/t/observe-field-on-multiple-select-box/175596/3 "2009-09-17T15:56:37Z")

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Hi All,

I found out the solution for this using following link.

1. [HTML/JavaScript - Reference all selected options in a multiple list - mredkj.com](http://www.mredkj.com/tutorials/tutorial004.html)
2. use following javascript to find out how many options are selected  
and pass it thorugh observe field.

Thanks & Regards,

Salil G.