Question

Let’s say we’re making a blog. Usually, the models look like this:

class User
  has_many :posts
end

class Post
  belongs_to :user
end

And their schemas look like:

User
  id

Post
  id
  user_id

But now, users can log in through Facebook/Twitter/etc, and we want a post to belong not to the User object, but rather to the combination of the provider and the uid of provider.

The new schema would look like:

User
  id
  provider
  uid

Post
  id
  user_provider
  user_uid

And I’m not sure how the models would look like:

class User
  has_many :posts, :foreign_key => ['user_provider', 'user_uid'] # Is this right??
end

class Post
  belongs_to :user, :class_name => User # Again, this is a guess...
end

Am I on the right track? What is the Rails way of doing this?

Answer 1

You cannot have composite primary keys in rails out of the box. Fot that I think you will have to use gems. I would advise you to find a workaround.

However to have a starting point, look here:

http://compositekeys.rubyforge.org/