nifty rails 3.0 methods

Daniel Willemse di 22 jun 10

So with the Rails 3.0 beta release as of late, I decided to try and play around with a new rails app. I’m pretty new to Ruby and Rails, so trying a new version of Rails (where they also changed routing, one of the things I personally have most problems with) was pretty challenging for me.

For those that haven’t yet checked out the new and cool stuff that’s available with rails 3, here’s some new code versus the 2.x version.
I had a fresh app in rails 2.3.5, which I tried to rebuild in rails 3.0.
In the old app for instance, there was code like:

Invoice.find(:all, :conditions => ["number > ?", 5])
or
Invoice.find(:all, :order => "number DESC")

While in the new and improved rails,
you can write it much easier like this:

Invoice.where("number > ?", 5) and
Invoice.order("number DESC")

The cool part about this, is that you can chain these new methods like this:

Invoice.order("number DESC").where("number > ?" 5)

This technique also works for named scopes. With rails 3.0, you can easily make a named scope as follows:

scope :above_1, where("number > 1")
scope :below_5, where("number < 5")
scope :above_1_and_below_5, above_1.below_5

There are more of these new methods and as I play more with rails 3.0 I’ll try and update

So besides making it easier for you to chain together find options, why would you use these above the find methods
in rails 2.x?
Well I found my answer in a railscast where it is explained that the find option has been revised.
http://railscasts.com/episodes/202-active-record-queries-in-rails-3
In the video, it is shown that for instance, Model.scope (Article.recent in the video) returns an active record relation instead of performing the query. And that the query is performed when you try and get the actual data.

I have not yet been able to reproduce the same queries as in the railscast so I’ve not figured out how it works.
When I do however, I’ll try and share my findings and post an update.

Daniel Willemse

(the code I use, which should show me an active record relation in the console)

class Invoice < ActiveRecord::Base
  scope :above_1, where("number > 1")
  scope :below_5, where("number < 5")
  scope :above_1_and_below_5, above_1.below_5
end

>> i = Invoice.above_2_and_below_5.all

returns:

=>#<Invoice id: 4, …. ….. ….. , updated_at: "2010-06-22 19:50:29">]

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