Creating multiple relationships in rails with same datatypes

Question

What I am trying to do is kind of like this:

I have datatypes "user" and "article" for instance. I want to have relationships between these two, but in more than one way.

So for instance, I'd like to let a user "like" or "bookmark" an article. So I need to have two relations in the database, one for users liking the article, and one for users bookmarking, so making a "user_article" table for instance won't be sufficient, correct?

What is the best way of going about doing this?

Answer 1

I'd suggest Bookmarking model that have bookmarking_type (note that type is reserved for RoR). Then you could has_many :bookmarkings and has_many :liked_articles, :through => :bookmarkings and has_many :bookmarks, :through => :bookmarkings. Of course you should add conditions or just join SQL to these assocations, but all should be good. I do believe there's even plugin for that, just can't recall the name atm.

Answer 2

What you are describing are "Data Models" not "Data Types". Data types = String, integer etc. If it is a Active Record Object it's a Data Model or a Active Record Model more specifically.

Eimantas pointed out you are describing a 2 "has_many" relationships but not "have_many" as written in his post. In his example the bookmarkings is called a join model. Remember you can place other things in the join model and use the relationships there to accomplish things. Say you want to have a bookmark order or a favorite rank- the join model is the idea spot for this.

Stripped down example:

class Article < ActiveRecord::Base
  has_many :users, :through => :user_bookmarks
end

class UserBookmark < ActiveRecord::Base
  belongs_to :user
  belongs_to :article
end

class User < ActiveRecord::Base
  has_many :user_bookmarks
  has_many :articles, :through => :user_bookmarks
end

Things to look at after getting the basics down: Counter caches - if you are doing counts they are your friend.

It is likely way easier and cleaner to just use these 2 join models rather than try to dive into polymorphism right now. After you get that up and running you could explore that next.