How to override activerecord's default attribute column associations?

Question

I'm working on a legacy database that is complete non-sense. I have a table called movie that contains columns with names like c00, c01, c02 and so on. The table also uses non-standard primary_keys. So I've created a class called movie like this:

class Movie < ActiveRecord::Base
  set_table_name "movie"
  set_primary_key "idMovie"

  belongs_to :media_file, :foreign_key => "idFile" 

  def title
    self.c00
  end

  def plot
    self.c01
  end
end

I'd like to be able to do something like Movie.find_by_title("Die Hard") and have it return the right result. Also I'd like to be able to say Movie.create(:title => "Die Hard"). How do I do this?

Answer 1

I think you want alias_attribute. Check out Brian Hogan's excellent presentation from RailsConf this year.

Answer 2

The find_by_* methods use reflection, so it just isn't going to happen with Rails out-of-the-box. You can, of course, define your own methods:

def self.find_by_title(title)
    first(:conditions => { :c00 => title })
end

The next step would be to iterate over a hash of column_aliases => real_columns to use as fodder for calls to alias_attribute and define_method.

Answer 3

You really just need a combination of Sarah's answer and Ben's answer:

class Movie < ActiveRecord::Base

  # gives you Movie.find_by_title
  # and lets you chain with other named scopes
  named_scope :find_by_title, lambda { |title| { :conditions => { :c00 => title } } }

  # gives you
  #   movie.title
  #   movie.title=(title)
  # and
  #   Movie.new(:title => title)
  alias_attribute :title, :c00

end