# How to get which field changed in observe\_form helper

**URL:** <https://www.ruby-forum.com/t/how-to-get-which-field-changed-in-observe-form-helper/156740>\
**Category:** Rails\
**Created:** [January 2, 2009, 9:09am UTC](https://www.ruby-forum.com/t/how-to-get-which-field-changed-in-observe-form-helper/156740 "2009-01-02T09:09:59Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![youhaodeyi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/b9bd4f/32.png) [@youhaodeyi](https://www.ruby-forum.com/u/youhaodeyi)\
**Post date:** [January 2, 2009, 9:09am UTC](https://www.ruby-forum.com/t/how-to-get-which-field-changed-in-observe-form-helper/156740/1 "2009-01-02T09:09:59Z")

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I use observe\_form to monitor all the fields in a form. But how can I  
get which field changed?

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**Author:** ![youhaodeyi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/b9bd4f/32.png) [@youhaodeyi](https://www.ruby-forum.com/u/youhaodeyi)\
**Post date:** [January 3, 2009, 7:03pm UTC](https://www.ruby-forum.com/t/how-to-get-which-field-changed-in-observe-form-helper/156740/2 "2009-01-03T19:03:43Z")

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You could save the form values to a session or flash and compare to  
the values from the form delivered by observe\_form. This would be  
especially easy if the form is based on an object.

Pepe