Rails - Oct 2005 - ActiveRecord relations and dynamic conditions

When using  ActiveRecord  ''has_many''  feature one can use
'':conditions''
criteria e.g.

class Contact < ActiveRecord::Base
 
        # assotiations
        belongs_to :company
        has_many :problems, :conditions => "some condition"
end

Is there any way how to dynamicly specify the condition in has_many 
statement ? 

Thanks for any advice,

David Marko

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Don''t specify :conditions in the has_many, but instead in .find

--  
-- Tom Mornini


On Oct 11, 2005, at 1:37 AM,
dmarko-KxaEA3z1jV+iEHBPiYQIQwC/G2K4zDHf@public.gmane.org wrote:
>
> When using  ActiveRecord  ''has_many''  feature one can use
> '':conditions'' criteria e.g.
>
> class Contact < ActiveRecord::Base
>
>         # assotiations
>         belongs_to :company
>         has_many :problems, :conditions => "some condition"
> end
>
> Is there any way how to dynamicly specify the condition in has_many  
> statement ?
>
> Thanks for any advice,
>
> David Marko
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>


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On 11-okt-2005, at 10:37,
dmarko-KxaEA3z1jV+iEHBPiYQIQwC/G2K4zDHf@public.gmane.org wrote:
>
> When using  ActiveRecord  ''has_many''  feature one can use
> '':conditions'' criteria e.g.
>
> class Contact < ActiveRecord::Base
>
>         # assotiations
>         belongs_to :company
>         has_many :problems, :conditions => "some condition"
> end
>
> Is there any way how to dynamicly specify the condition in has_many  
> statement ?
I think you can use "lazy evaluation" in the form of

:condition=>''some_column = {condition_method_on_model}''

-- 
Julian "Julik" Tarkhanov

Hmm, but model methods have no access to  ''controller'' objects
like
''session'' is. To be more specific I want to  filter data based
on current
logged user to be sure that anly allowed data are listed. Users info is 
stored in session  and  model methods have no access to it. 

David Marko




"Julian ''Julik'' Tarkhanov"
<listbox-RY+snkucC20@public.gmane.org>
Sent by: rails-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
11.10.2005 15:06
Please respond to
rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org


To
rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
cc

Subject
Re: [Rails] ActiveRecord relations and dynamic conditions







On 11-okt-2005, at 10:37,
dmarko-KxaEA3z1jV+iEHBPiYQIQwC/G2K4zDHf@public.gmane.org wrote:
>
> When using  ActiveRecord  ''has_many''  feature one can use
> '':conditions'' criteria e.g.
>
> class Contact < ActiveRecord::Base
>
>         # assotiations
>         belongs_to :company
>         has_many :problems, :conditions => "some condition"
> end
>
> Is there any way how to dynamicly specify the condition in has_many 
> statement ?
I think you can use "lazy evaluation" in the form of

:condition=>''some_column = {condition_method_on_model}''

-- 
Julian "Julik" Tarkhanov

_______________________________________________
Rails mailing list
Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
http://lists.rubyonrails.org/mailman/listinfo/rails



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On 11-okt-2005, at 15:14,
dmarko-KxaEA3z1jV+iEHBPiYQIQwC/G2K4zDHf@public.gmane.org wrote:
>
> Hmm, but model methods have no access to  ''controller''
objects like
> ''session'' is. To be more specific I want to  filter data
based on
> current logged user to be sure that anly allowed data are listed.  
> Users info is stored in session  and  model methods have no access  
> to it.
>
>
Yes, this decoupling is there intentionally and personally I think  
it''s right. I also encountered this problem, for now I see only these  
solutions.

1. I implement a kind of a security filter, which can do things like

if @filter.can_view?(@loaded_object)
  proceed...
else
  deny
end

This it an object that gets loaded with the controller and is  
constructed passing it a User model on creation. Then in this object  
I quickly write "delegate" actions that deal with specific models,  
for example

begin
     @filter.update_attributes(@job, params[:job])
rescue PermissionError
     #it is forbidden
end

In the filter I can define methods like "can_view_support_ticket? 
(ticket)"  or "can_update_notice?(notice)"

The object will by itself dispatch a question about permissions to  
this method if it gets a SupportTicket object.

This is in a way similar to the recently posted Model Security  
tutorial - I think it''s indeed wise to delegate security management  
to a separate class/object instead of making your controllers  
checking each and ever condition.

What you might use is simply a find method on the collection, like

Technician.find(3).support_tickets.find("owner_id = #{@user.id}")

-- 
Julian "Julik" Tarkhanov

It''s a bit of a hack, but adding a before_filter to your application
controller like this:

before_filter :assign_session
<snip>
def assign_session
    $session = session
end

Will allow you access to your session in your models through $session.
Of course, this probably violates the principles of MVC, as you have
controller code in your models.

Elliot

On 11/10/05, dmarko-KxaEA3z1jV+iEHBPiYQIQwC/G2K4zDHf@public.gmane.org
<dmarko-KxaEA3z1jV+iEHBPiYQIQwC/G2K4zDHf@public.gmane.org>
wrote:
>
> Hmm, but model methods have no access to  ''controller''
objects like
> ''session'' is. To be more specific I want to  filter data
based on current
> logged user to be sure that anly allowed data are listed. Users info is
> stored in session  and  model methods have no access to it.
>
> David Marko
>
>
>
>
>  "Julian ''Julik'' Tarkhanov"
<listbox-RY+snkucC20@public.gmane.org>
> Sent by: rails-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
>
> 11.10.2005 15:06
>
> Please respond to
>  rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
>
>
> To rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
>
> cc
>
> Subject Re: [Rails] ActiveRecord relations and dynamic conditions
>
>
>
>
>
>
>  On 11-okt-2005, at 10:37,
dmarko-KxaEA3z1jV+iEHBPiYQIQwC/G2K4zDHf@public.gmane.org wrote:
>
>  >
>  > When using  ActiveRecord  ''has_many''  feature one
can use
>  > '':conditions'' criteria e.g.
>  >
>  > class Contact < ActiveRecord::Base
>  >
>  >         # assotiations
>  >         belongs_to :company
>  >         has_many :problems, :conditions => "some
condition"
>  > end
>  >
>  > Is there any way how to dynamicly specify the condition in has_many
>  > statement ?
>
>  I think you can use "lazy evaluation" in the form of
>
>  :condition=>''some_column =
{condition_method_on_model}''
>
>  --
>  Julian "Julik" Tarkhanov
>
>  _______________________________________________
>  Rails mailing list
>  Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
>  http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>