Rails - Jul 2006 - Weird problem. How to tell if an attribute has changed? Please help.

How do you tell if an foreign key attribute has been changed?

For example, lets say you have a model with attribute table_a_id.  
Would you do this?

def table_a_id=(value)
     if value != table_a_id
       @table_a_changed = true
       write_attribute ''table_a_id'', value
     end
   end

   def table_a=(value)
     if value != table_a
       @table_a_changed = true
       @table_a = value
     end
   end

I did this and when I try to save the model I get ''undefined method  
updated?''. What am I doing wrong here? Or is there a better way to  
determine if an attribute has changed? The reason I''m doing this is  
because in my after_save method I need to run some special code if  
the relationship has changed.

Thanks a lot for your help.


Thank You,
Ben Johnson
E: bjohnson@contuitive.com



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Adding a side-effect to the mutators seems like the way to go: that''s 
what mutators are for. I''m a little unsure about updating each
attribute
immediately (which write_attribute() seems to do).

Also, where do you resent @table_a_changed ?

Are you sure it is not talking about a method named "updated?".
I''ve had
hours of fun working out what ruby error message are actually talking 
about.

Ben Johnson wrote:
>def table_a_id=(value)
>     if value != table_a_id
>       @table_a_changed = true
>       write_attribute ''table_a_id'', value
>     end
>   end
> ...
> I did this and when I try to save the model I get ''undefined
method
> updated?''. What am I doing wrong here? Or is there a better way to
> determine if an attribute has changed? 
Cheers


-- 
Posted via http://www.ruby-forum.com/.

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On Wed, Jul 12, 2006 at 02:17:32PM -0500, Ben Johnson
wrote:
> How do you tell if an foreign key attribute has been changed?
It sounds like the acts_as_modified plugin is what you want:
http://svn.viney.net.nz/things/rails/plugins/acts_as_modified/

- --
Peter Harkins  -  http://push.cx


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