Associating a resource with multiple resources?

Hi,

I have these models in my ror application: author, article and book. I
want to associate author to article and book so:

book has many authors
article has many authors
author belongs to both of them

What’s the best practice for doing so? Should I have both book_id and
article_id in author table? Other solutions?

Thanks in advance,

Houman,

I think you want a has_many :through relationship. Here is an analogy:

http://wiki.rubyonrails.org/rails/pages/Beginner+Howto+on+has_many+:through

Arshak

Houman D. wrote:

Hi,

I have these models in my ror application: author, article and book. I
want to associate author to article and book so:

book has many authors
article has many authors
author belongs to both of them

What’s the best practice for doing so? Should I have both book_id and
article_id in author table? Other solutions?

Thanks in advance,

If you have reasons to stick with the current model, then introduce a
fourth concept, call it ‘Publishing’. A ‘publishing’ is something
that an author has written. In this case, it associates an author to
a book or an article. Now you can use two techniques –
has_many :through (as suggested by Arshak) and polymorphic
associations.

create_table :publishing do |t|
t.reference :publishable, :polymorphic=>true
t.reference :author
end

class Publishing < ARec::Base
belongs_to :author
belongs_to :publishable, :polymorphic=>true

end

class Author < ARec::Base
has_many :publishings

end

class Book < ARec::Base
has_many :publishings, :as=>:publishable
has_many :authors, :through=>:publishing

end

class Article < ARec::Base
has_many :publishings, :as=>:publishable
has_many :authors, :through=>:publishing

end

The other possibility would be to use Single Table Inheritance,
putting the books and articles into a single table that uses a
discriminator column so that you can tell them apart. You can still
use the has_many :through concept (to support 1 or more authors) but
you eliminate one table.

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