Forum: Ruby on Rails Cache Magic field for totaling

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Surendra S. (Guest)
on 2006-02-28 14:38
(Received via mailing list)
Hello,
 Rails provide counter cache field for associations, I want a similar
cache
for totaling up values
(say account_balance = sum_of_deposits - sum_of_withdrawals).

I was wondering if rails, already has another surprise in store for me,
or is
there any plug-in or how-to for doing these kind of things.

Thanks.

--
Surendra S.
http://ssinghi.kreeti.com, http://www.kreeti.com
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Surendra S. (Guest)
on 2006-03-03 16:08
(Received via mailing list)
Surendra S. <removed_email_address@domain.invalid> writes:

>  Rails provide counter cache field for associations, I want a similar cache
> for totaling up values
> (say account_balance = sum_of_deposits - sum_of_withdrawals).

OK. I went ahead and wrote something of my own. For this purpose I had
to
extend the rails internal a bit, it is working but I was wondering
whether I
have done things the right way.

[1] Is there any way of adding one more option to the 'belongs_to'
declaration? I didn't find any so I wrote my own declaration titled
'belongs_to_opt'. But there is a little bit of redundancy in the my
implementation of `belongs_to_opt' and rails internal `belongs_to', I
was
wondering if there was a way of getting rid of that.

[2]In the rails wiki to extend ActiveRecords `append_features' is used
http://wiki.rubyonrails.com/rails/pages/ExtendingA...

I was wondering shouldn't it be `included', because in the Pragmatic
book it
is mentioned that `included' is the preferred way.

I have extended ActiveRecords in the following way, does it follows the
convention, does the style of extending looks OK?

module ActiveRecord
  module Associations # :nodoc:
    def self.append_features(base)
      super
      base.extend(ClassMethods)
    end

    module ClassMethods
      def belongs_to_opt(association_id, options = { })
               .......
    end

    class AssociationCollection
       ....
    end
  end
end

It is my first foray into peeking at the rails core, and I am really
impressed
by the clarity of the code. It was so easy to understand and grasp the
flow. My first impression is that Rails not only helps in writing
beautiful
code, but itself is written beautifully.

Any tips will be appreciated.
Thanks.

--
Surendra S.
http://ssinghi.kreeti.com, http://www.kreeti.com
Read the latest news at: http://news.kreeti.com
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| And thin partitions do their bounds divide.
|
|     (John Dryden, Absalom and Achitophel, 1681)
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