Rails - Apr 2006 - validation on before_add callback

problem: validation error is not functionning in callback

callback for many-to-many association:

# keyword.rb
:before_add => :reject_self_related


    def reject_self_related(related_keyword)
        if (related_keyword == self)
# this does not work:
            errors.add(:name, "Relating a keyword to itself is 
forbidden!")
            raise "Relating a keyword to itself is forbidden!"
        end
    end


in the keyword.rhtml form:

<%= error_messages_for ''keyword'' %>

does not display the error message.

what am I doing wrong?

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Isabelle wrote:

Hi Isabelle,

First off, is the callback being triggered at all ?  If you replace the 
whole body with the raise, do you see the exception ?

Second, if you just replace the body with the errors.add, do you see the 
error ?

Last, == on Object tests for the exact same Object, I think ActiveRecord 
override this to compare ids, if the new item hasn''t yet been saved,
the
== method will return false.  Perhaps you need to check, say 
keyword.text, or whatever the property is that stores the text.

Alan

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Alan Francis wrote:
> Isabelle wrote:
> 
> Hi Isabelle,
> 
> First off, is the callback being triggered at all ?  If you replace the 
> whole body with the raise, do you see the exception ?
yes. I can catch the exception in the controller and display the 
exception message:

# keywords_controller.rb

        # attempt to add item to list
        begin
          @keyword.related_keywords<< @related
        rescue Exception
          # extract error messages from the global variable
          # representing the Exception object
          flash[:notice] = $!.message
        end
> Second, if you just replace the body with the errors.add, do you see the 
> error ?
no, and the object that should not have been saved is saved.
> Last, == on Object tests for the exact same Object, I think ActiveRecord 
> override this to compare ids, if the new item hasn''t yet been
saved, the
> == method will return false.  Perhaps you need to check, say 
> keyword.text, or whatever the property is that stores the text.
I see your point. In my case the callback is before adding an existing 
item to a collection that is defined as a self-referential 
has_and_belongs_to_many relation.


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> I see your point. In my case the callback is before adding an existing 
> item to a collection that is defined as a self-referential 
> has_and_belongs_to_many relation.
I''d reckon that''s the problem then, and would compare the
attribute,
rather than the object.


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Alan Francis wrote:
> 
>> I see your point. In my case the callback is before adding an existing 
>> item to a collection that is defined as a self-referential 
>> has_and_belongs_to_many relation.
> 
> I''d reckon that''s the problem then, and would compare the
attribute,
> rather than the object.
tried it and still the errors.add() is not executed

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