models - 'find'-ing by a method

rubyonrails-talk
#1

wondering if there is a way to do this..

say we have a model that has attributes length and width..

:length and :width

and we have a class square:

class Square < ActiveRecord::Base

  def area
    area = length * width
  end

end

is there a way i can do a:

Square.find(:area => '144')

to produce any squares with an area of 144?

i know there are lots of other ways to do this, but in the case i am
working on, a find would be REALLY clean..

#2

Not directly (although clearly you could write Square.where('length *
width = 144'), or define a named scope that does this. you also can't
use indexes for queries like this (unless your db supports functional
indexes)

Fred

#3

wondering if there is a way to do this…

say we have a model that has attributes length and width…

:length and :width

and we have a class square:

class Square < ActiveRecord::Base

def area

area = length * width

end

end

is there a way i can do a:

Square.find(:area => ‘144’)

You can always use your db’s arithmetic operators, for mysql you can look at

http://dev.mysql.com/doc/refman/5.0/en/arithmetic-functions.html

#4

thanks, guys!

i ended up just writing a method for the model that does the check..
it's something that would only happen maybe once a week.. and then,
maybe only one or two transactions.