Forum: Ruby on Rails Use callbacks to determine model field changes?

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3ff9c2544554b13c6c7877e76684751b?d=identicon&s=25 Lee Smith (smitjel)
on 2009-05-27 16:26
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What's the best way to examine what fields on a model are changing?
Would you use a callback to do that and how?

I guess the simplest example of this is how lighthouseapp documents
changes that a person makes to a ticket:

Milestone changed from “2.x” to “3.0”

State changed from “new” to “open”

How could I accomplish the same thing?
8cac6e764279d4ca612f4a6ec767fdaf?d=identicon&s=25 Benjamin Curtis (Guest)
on 2009-05-27 16:32
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Take a look at
ActiveRecord::Dirty<http://api.rubyonrails.org/classes/ActiveRecord/Di...
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Benjamin Curtis
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B14575f0ca69f10938fdd67e7156e0e1?d=identicon&s=25 Craig Demyanovich (Guest)
on 2009-05-27 16:32
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If you're on Rails >= 2.1, you can track attribute changes:

http://api.rubyonrails.org/classes/ActiveRecord/Dirty.html

You might also like Ryan Bates' screencast on the topic:

http://railscasts.com/episodes/109-tracking-attrib...

Regards,
Craig


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Craig Demyanovich
Mutually Human Software
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3ff9c2544554b13c6c7877e76684751b?d=identicon&s=25 Lee Smith (smitjel)
on 2009-05-28 20:16
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Thanks for the help guys.

However, I've now hit the trap where I need session data in the
observer (who is changing the model)...
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