Joining the same model twice in a clean way, but making the code reusable
- by Shako
I have a model Painting which has a Paintingtitle in each language and a Paintingdescription in each language:
class Painting < ActiveRecord::Base
has_many :paintingtitles, :dependent => :destroy
has_many :paintingdescriptions, :dependent => :destroy
end
class Paintingtitle < ActiveRecord::Base
belongs_to :painting
belongs_to :language
end
class Paintingdescription < ActiveRecord::Base
belongs_to :painting
belongs_to :language
end
class Language < ActiveRecord::Base
has_many :paintingtitles, :dependent => :nullify
has_many :paintingdescriptions, :dependent => :nullify
has_many :paintings, :through => :paintingtitles
end
As you might notice, I reference the Language model from my Painting model via both the Paintingtitle model and Paintingdescription model. This works for me when getting a list of paintings with their title and description in a specific language:
cond = {"paintingdescription_languages.code" => language_code, "paintingtitle_languages.code" => language_code}
cond['paintings.publish'] = 1 unless admin
paginate(
:all,
:select => ["paintings.id, paintings.publish, paintings.photo_file_name, paintingtitles.title, paintingdescriptions.description"],
:joins => "
INNER JOIN paintingdescriptions ON (paintings.id = paintingdescriptions.painting_id)
INNER JOIN paintingtitles ON (paintings.id = paintingtitles.painting_id)
INNER JOIN languages paintingdescription_languages ON (paintingdescription_languages.id = paintingdescriptions.language_id)
INNER JOIN languages paintingtitle_languages ON (paintingtitle_languages.id = paintingtitles.language_id) ",
:conditions => cond,
:page => page,
:per_page => APP_CONFIG['per_page'],
:order => "id DESC"
)
Now I wonder if this is a correct way of doing this. I need to fetch paintings with their title and description in different functions, but I don't want to specify this long join statement each time. Is there a cleaner way, for instance making use of the has_many through? e.g.
has_many :paintingdescription_languages, :through => :paintingdescriptions, :source => :language
has_many :paintingtitle_languages, :through => :paintingtitles, :source => :language
But if I implement above 2 lines together with the following ones, then only paintingtitles are filtered by language, and not the paintingdescriptions:
cond = {"languages.code" => language_code}
cond['paintings.publish'] = 1 unless admin
paginate(
:all,
:select => ["paintings.id, paintings.publish, paintings.photo_file_name, paintingtitles.title, paintingdescriptions.description"],
:joins => [:paintingdescription_languages, :paintingtitle_languages],
:conditions => cond,
:page => page,
:per_page => APP_CONFIG['per_page'],
:order => "id DESC"
)
