Ruby Fleebie » Use named_scope to add elegant finders to your models

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Use named_scope to add elegant finders to your models

Aug 20, 2008 @ 12:46 pm

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I used to be a fan of the has_finder gem written by Nick Kallen.

Now with Rails 2.1, this functionnality is built-in so you don’t need to install the gem.

The named_scope method allows you to add finders to any model. A code snippet is worth 10000 words :

class Story < ActiveRecord::Base
  named_scope :hilarious, :conditions => ["type = ?","comedy"]
  named_scope :popular, :conditions => ["popularity_level > ?", 3]
end

Doing this you can chain expressions like this :

funny_stories = @all_stories.hilarious
funny_and_popular = @all_stories.hilarious.popular

Maybe you knew it, maybe you didn’t. If you didn’t, now you know it. (I feel very smart about this last sentence. I think I am going to put this in my room somewhere)

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Posted under : short & sweet

2 Comments

MyAvatars 0.2

Minor nitpick: named_scope was introduced in Railes 2.1, so anyone using Rails 2.0.2 (like me) still has to use has_finder.

Comment by : pete

— August 20, 2008 @ 2:42 pm

MyAvatars 0.2

Thanks for the precision Pete. I’m going to update the original post.

Comment by : Frank

— August 20, 2008 @ 3:10 pm

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