[Rails] What is best way to define AR scope for this?

[Michael Bostler]

Hi all,


Say I have an article class that has one main tag, but can also be
associated with multiple secondary tags. Something like schema listed
below. How can I implement the scope method below?


Basically I want one method where I can return ALL articles related to a
tag, regardless of whether it is a primary tag relationship or secondary
tag relationship.


Many Thanks!


class Article < ActiveRecord::Base
  belongs_to :primary_tag,
             :class_name => "Tag"

  has_many :secondary_tag_listings

  has_many :secondary_tags,
           :through     => :secondary_tag_listings,
           :class_name  => "Tag"

  scope :all_with_tag, lambda { |tag_name|
    # TODO: how to find all with either primary OR secondary tags
    #       as tag_name?
  }
end




class SecondaryTagListings < ActiveRecord::Base
  belongs_to :article
  belongs_to :tag
end




class Tag < ActiveRecord::Base
  has_many :primary_articles,
           :class_name => "Article"

  has_many :secondary_tag_listings

  has_many :secondary_articles,
           :through     => :secondary_tag_listings,
           :class_name  => "Article"
end

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