Silence is Foo Mental notes on Ruby/Git/Rails/Flex

Mimicking Rails 3’s ActiveRecord query interface in Rails 2.x

NOTICE: This is only for educational and fun purposes, nothing else. I'm not trying to say that you'll get all the pros of the new query interface in Rails 2.x, it isn't even close.

The first time I used the new ActiveRecord query interface (Rails 3) I started to get boring with the one in Rails 2.x, I can't do anything, I have to use the old query interface since converting my projects from Rails 2 to Rails 3 is not an option, so I thought to make a sort of placebo, just for fun, just to be used in my local console, and here is.

module FakeActiveRecord3Methods
  def self.included(base)
    base.class_eval do
      %w/select group order limit offset joins having/.each do |method|
        named_scope method.to_sym, lambda { |arg| { method.to_sym => arg } }
      end

      named_scope :where, lambda { |arg| { :conditions => arg } }
      named_scope :includes, lambda { |arg| { :include => arg } }
    end
  end
end

Click here to see a Gist in GitHub

I used named scopes because they are chainable, if I would have added instance methods to ActiveRecord::Base it would haven't worked as I want to, maybe there's a way to make it work that way, but this was a 5-minutes module, I didn't want to spent too much time on it.

well, I have to say I don't use this module in production servers, only locally in development mode. This is how I configure my development environment to use it:

In my environment/development.rb

config.after_initialize do
  [User, And, All, The, Models, You, Want].each do |model|
    model.class_eval do
      include FakeActiveRecord3Methods
    end
  end
end

Click here to see a Gist in GitHub

I add the models I use the most, if I need to use the FakeActiveRecord3Methods module in other model I include it in the console. To make this even easier I added to my ~/.irbrc the following code:

class Class
    public :include
end

It allows us to include a module this way:

Profile.include FakeActiveRecord3Methods

otherwise Ruby will throw an exception saying we're trying to access a private method.

It might seem cumbersome to make all of this but it isn't that hard.

It's a shame I won't be able to prove that FakeActiveRecord3Methods works in most of the cases but you can test with the examples shown in Rails Guides: Active Record Querying.

Here are some queries using this module anyways. I think all of them are self-explanatory.

User.select("id, email").limit(2)
=> [#<User id: 1, email: "e@mail.com">, #<User id: 2, email: "bar@foo.com">]

User.select("id, email").where(["created_at > ?", 1.month.ago]).order("email DESC").limit(1)
=> [#<User id: 5, email: "foo@bar.com">

User.limit(5)

User.select(:id)

User.select(:id).limit(10).offset(100)

User.order :created_at

Joins

users = User.select("users.id, profiles.company").joins(:profile)
users.first.company # => Foo Company

users.first.profile.company # => Foo Company

Includes

users = User.limit(10)
users.first.name # => Foo
users.first.profile.company # => it will query the database

users = User.includes(:profile).limit(10) # it will bring the profile as well
users.first.profile.company # it won't query the database

Of course, you should be aware that in named scopes the order really matters, be careful and remember, in Rails 3, the where, select, group, order, limit, offset, joins and includes returns an instance of ActiveRecord::Relation which is not the case in the FakeActiveRecord3Methods module, it returns an instance of ActiveRecord::NamedScope::Scope and that's because named scopes returns an instance of such class.

By the way, if you want to read the Rails 2's ActiveRecord Query Interface, you can do so clicking here

Thanks for reading.