Rails - Apr 2006 - Added method to ActiveRecord Class

Hi,

Let''s say:

class Class2 << ActiveRecord
   belongs_to: class1
end

class Class1 << ActiveRecord
    has_many :class2s

    def get_max_class2
        ?how to get the max of class2 list ?
    end
end

I would like to know how I have to write the get_max_class2 method
in order to have the max value of the class2 list ?

I would like to call this method this way:
class2_max = class1.get_max_class2

Any ideas ? Thanks a lot in advance
Regards
Seb

On Apr 4, 2006, at 3:15 AM, Sebastien Hugues wrote:

Well, it does depend on what you really mean by "max", but...
> Hi,
>
> Let''s say:
>
> class Class2 << ActiveRecord
>    belongs_to: class1
> end
>
> class Class1 << ActiveRecord
>     has_many :class2s
>
>     def get_max_class2
>         ?how to get the max of class2 list ?
        self.class2s.max	# if <=> is well-defined for Class2
otherwise, the max ''id'' like:
        self.class2s.max { |a,b| a.id <=> b.id }
>     end
> end
>
> I would like to know how I have to write the get_max_class2 method
> in order to have the max value of the class2 list ?
>
> I would like to call this method this way:
> class2_max = class1.get_max_class2
>
> Any ideas ? Thanks a lot in advance
> Regards
> Seb
Of course, you could also:

class Class1 << ActiveRecord::Base
   has_many :class2s
   has_one  :max_class2, :class_name => "Class2", :order =>
"id DESC"

   # the max_class2 then is free, but if you insist
   def get_max_class2
     self.max_class2
   end
end

Look at:  http://api.rubyonrails.org/classes/ActiveRecord/ 
Associations/ClassMethods.html#M000531

(I did!)

-Rob

Rob Biedenharn
Rob@AgileConsultingLLC.com
--------------------------
"I sort of keep hoping that red herrings will steadilly come along,  
to keep people busy; I get secret satisfaction when bad ideas take  
hold and suck a lot of people in ... like Java."
-- Don Knuth, Things a Computer Scientist Rarely Talks About, p.16  
(Stanford, California: CSLI Publications, 2001)