Rails - Jul 2007 - Setting a callback whose action depends on the previous state of the object

I''ve been reading about ActiveRecord::Callbacks and they''re
really
cool. But I have a complex need I''m not sure they answer.

Let''s say we have a User model. User has a #status attribute, which
can be either "active", "closed" or "blocked".

I want to set a callback to perform an action if an "active" User has
been blocked. So I need to know:

1. That the user has at first been in "active" status.
2. That his status has been set to "blocked".

I need to set the callback when someone tries to save him in this
state, so to sum up:

I need to run some logic when someone updates a user.status from
''active'' to ''blocked''.

Any idea how?

--
Maurice B. Gladwell

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On Jul 7, 2007, at 5:49 PM, Maurice Gladwell wrote:
> Let''s say we have a User model. User has a #status attribute,
which
> can be either "active", "closed" or
"blocked".
>
> I want to set a callback to perform an action if an "active" User
has
> been blocked. So I need to know:
>
> 1. That the user has at first been in "active" status.
> 2. That his status has been set to "blocked".
>
> I need to set the callback when someone tries to save him in this
> state, so to sum up:
>
> I need to run some logic when someone updates a user.status from
> ''active'' to ''blocked''.
>
> Any idea how?
>
> --
> Maurice B. Gladwell
Thinking completely off the top of my head (e.g., none of this has  
actually been run), I''d say you could hook into the status writer and  
set a flag for later use in a before_save callback.

before_save :handle_newly_blocked

def status=(new_status)
   if self.status == ''active'' && new_status ==
''blocked''
     @newly_blocked = true
   end
   write_attribute(:status, new_status)
end

def handle_newly_blocked
   if @newly_blocked
     #  .. handle it ..
   end
end


-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org




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Maurice Gladwell wrote:
> I''ve been reading about ActiveRecord::Callbacks and
they''re really
> cool. But I have a complex need I''m not sure they answer.
> 
> Let''s say we have a User model. User has a #status attribute,
which
> can be either "active", "closed" or
"blocked".
> 
> I want to set a callback to perform an action if an "active" User
has
> been blocked. So I need to know:
> 
> 1. That the user has at first been in "active" status.
> 2. That his status has been set to "blocked".
> 
> I need to set the callback when someone tries to save him in this
> state, so to sum up:
> 
> I need to run some logic when someone updates a user.status from
> ''active'' to ''blocked''.
> 
> Any idea how?
> 
> --
> Maurice B. Gladwell
I don''t know how you are going to use this function,
but maybe you''re going to use it this way.

A user presses the "block" button.
this calls the "block!" method on the user,
execute whatever code you need.

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

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On 8-Jul-07, at 4:59 PM, Matthew Rudy wrote:
>
> Maurice Gladwell wrote:
>> I''ve been reading about ActiveRecord::Callbacks and
they''re really
>> cool. But I have a complex need I''m not sure they answer.
>>
>> Let''s say we have a User model. User has a #status attribute,
which
>> can be either "active", "closed" or
"blocked".
>>
>> I want to set a callback to perform an action if an "active"
User has
>> been blocked. So I need to know:
>>
>> 1. That the user has at first been in "active" status.
>> 2. That his status has been set to "blocked".
>>
>> I need to set the callback when someone tries to save him in this
>> state, so to sum up:
>>
>> I need to run some logic when someone updates a user.status from
>> ''active'' to ''blocked''.
>>
>> Any idea how?
>>
>> --
>> Maurice B. Gladwell
>
> I don''t know how you are going to use this function,
> but maybe you''re going to use it this way.
>
> A user presses the "block" button.
> this calls the "block!" method on the user,
> execute whatever code you need.
>
Although your example is a simple state machine, I am a big fan of  
acts_as_state_machine.

http://lunchroom.lunchboxsoftware.com/2006/1/21/acts-as-state-machine

Jodi



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Sorry for the late response, but I couldn''t resist telling you to look
at the acts_as_state_machine plugin. It lets you program transition
logic like you''re describing declaratively.

On 7/7/07, Maurice Gladwell
<maurice.gladwell-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> I''ve been reading about ActiveRecord::Callbacks and
they''re really
> cool. But I have a complex need I''m not sure they answer.
>
> Let''s say we have a User model. User has a #status attribute,
which
> can be either "active", "closed" or
"blocked".
>
> I want to set a callback to perform an action if an "active" User
has
> been blocked. So I need to know:
>
> 1. That the user has at first been in "active" status.
> 2. That his status has been set to "blocked".
>
> I need to set the callback when someone tries to save him in this
> state, so to sum up:
>
> I need to run some logic when someone updates a user.status from
> ''active'' to ''blocked''.
>
> Any idea how?
>
> --
> Maurice B. Gladwell
>
> >
>

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-Pre-order my book The Rails Way
http://www.amazon.com/dp/0321445619

blog: http://jroller.com/obie/

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