Rails - Mar 2007 - Order by dynamic field

Hello,

If I have the following model:

class MyModel < ActiveRecord::Base
  def self.some_calculations(id)
     .....
  end
end

Is it possible to use MyModel.find() and order the results by my defined
method self.some_calculations(id)?

--
Thanks in advance,
Justas

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

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On Mar 11, 2007, at 11:52 AM, Justas wrote:
> If I have the following model:
>
> class MyModel < ActiveRecord::Base
>   def self.some_calculations(id)
>      .....
>   end
> end
>
> Is it possible to use MyModel.find() and order the results by my  
> defined
> method self.some_calculations(id)?
To accomplish that you need to fetch all the involved rows, and order  
the objects in Ruby land:

   @models = MyModel.find_all_by_foo(foo).sort {|a, b| ... }

Of course that may be too expensive, depending on the amount of data.  
If that was the case, you could consider maintaining those  
calculations via AR callbacks and cache them in some column. That  
way, you''d delegate ordering to the database.

-- fxn


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Yes, why not?

class MyModel < ActiveRecord::Base
  def self.some_calculations(id)
     find(:all, :conditions => [''id != ?'', id], :order
=> ''rand()'')
  end
end
>> MyModel.some_calculations(66)
OR drop the self and have an instance method....

class MyModel < ActiveRecord::Base
  def some_calculations
     find(:all, :conditions => [''id != ?'', id], :order
=> ''rand()'')
  end
end
>> MyModel.find(66).some_calculations
On Mar 11, 6:52 pm, Justas
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> Hello,
>
> If I have the following model:
>
> class MyModel < ActiveRecord::Base
>   def self.some_calculations(id)
>      .....
>   end
> end
>
> Is it possible to use MyModel.find() and order the results by my defined
> method self.some_calculations(id)?
>
> --
> Thanks in advance,
> Justas
>
> --
> Posted viahttp://www.ruby-forum.com/.

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On Mar 11, 2007, at 3:10 PM, eden li wrote:
> class MyModel < ActiveRecord::Base
>   def self.some_calculations(id)
>      find(:all, :conditions => [''id != ?'', id], :order
=> ''rand()'')
>   end
> end
Justas wants to order the rows according to the result of applying  
some_calculations() to them.

-- fxn




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