Rails - Oct 2007 - How to hook into model attribute changes?

Hi,

What''s the best way to hook into any changes made to the value of a
single model attribute? I need to know when the encrypted_password
attribute on my User model changes i.e. when the user has changed their
password. I''m not interested in the actual changed value, I just need
to
know when it''s been changed so that I can regenerate their API key as
well.

Thanks in advance.

John
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Hi John


On Oct 22, 7:28 pm, John Topley
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> Hi,
>
> What''s the best way to hook into any changes made to the value of
a
> single model attribute? I need to know when the encrypted_password
> attribute on my User model changes i.e. when the user has changed their
> password. I''m not interested in the actual changed value, I just
need to
> know when it''s been changed so that I can regenerate their API key
as
> well.
cch: You should look into callbacks. For example, I use

  def after_update(record)
    log(record, "UPDATE")
  end

to record whether a change has been made

>
> Thanks in advance.
>
> John
> --
> Posted viahttp://www.ruby-forum.com/.

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CCH wrote:
> Hi John
> 
> 
> On Oct 22, 7:28 pm, John Topley
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
> wrote:
>> Hi,
>>
>> What''s the best way to hook into any changes made to the value
of a
>> single model attribute? I need to know when the encrypted_password
>> attribute on my User model changes i.e. when the user has changed their
>> password. I''m not interested in the actual changed value, I
just need to
>> know when it''s been changed so that I can regenerate their API
key as
>> well.
> 
> cch: You should look into callbacks. For example, I use
> 
>   def after_update(record)
>     log(record, "UPDATE")
>   end
> 
> to record whether a change has been made
Thanks. I did try that but the problem is that the user can change other 
settings on the screen that lets them change their password and the API 
key musn''t be regenerated if those other settings are changed. Hence, I
need to detect a changed password only.

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You could try using this plugin and a callback (after_update maybe?)
to determine when to regenerate the API key:

http://svn.viney.net.nz/things/rails/plugins/acts_as_modified/README

On Oct 22, 8:46 am, John Topley
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> CCH wrote:
> > Hi John
>
> > On Oct 22, 7:28 pm, John Topley
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
> > wrote:
> >> Hi,
>
> >> What''s the best way to hook into any changes made to the
value of a
> >> single model attribute? I need to know when the encrypted_password
> >> attribute on my User model changes i.e. when the user has changed
their
> >> password. I''m not interested in the actual changed value,
I just need to
> >> know when it''s been changed so that I can regenerate
their API key as
> >> well.
>
> > cch: You should look into callbacks. For example, I use
>
> >   def after_update(record)
> >     log(record, "UPDATE")
> >   end
>
> > to record whether a change has been made
>
> Thanks. I did try that but the problem is that the user can change other
> settings on the screen that lets them change their password and the API
> key musn''t be regenerated if those other settings are changed.
Hence, I
> need to detect a changed password only.
>
> --
> Posted viahttp://www.ruby-forum.com/.

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Thanks Andrew, I''ll try that out.

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John Topley wrote:
> What''s the best way to hook into any changes made to the value of
a
> single model attribute? I need to know when the encrypted_password
> attribute on my User model changes i.e. when the user has changed their
> password. I''m not interested in the actual changed value, I just
need to
> know when it''s been changed so that I can regenerate their API key
as
> well.
Something like

class User
   def encrypted_password=(ep)
     self.api_key = API.gen_key(ep) # if ep != encrypted_password
     super
   end
end

The condition isn''t necessary in this case because the
encrypted_password is only set if a password change is
detected, not on every form submission by the user.

-- 
We develop, watch us RoR, in numbers too big to ignore.


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