Activerecord has_many :through through multiple models

Question

I\'m trying to access all comments from a given user with user.comments. The query is to go through two different models, which likely both return results. My r

Answer 1

I believe your associations would be confused, as user.comments wouldn't know whether it's going through Participant or Organiser, so the best option would be to declare two different joins (with different names):

http://guides.rubyonrails.org/association_basics.html#self-joins

Answer 2

Since we couldn't use has_many, through here because comments come from both of organisers and participants. I just think there are 2 solutions here:

Solution #1 Define comments method:

class User < ActiveRecord::Base
  def comments
    Comment.joins([{organiser: :user}, {participant: :user}])
           .where(users: {id: self.id})
  end
end

So then your query to find comments is:

User.first.comments

Solution #2 Use scope in Comment

class Comment < ActiveRecord::Base
  scope :from_user, -> (user) { 
    joins([{organiser: :user}, {participant: :user}]).where(users: {id: user.id}) 
  }
end

So your query will be like:

user = User.first
comments = Comment.from_user(user)

Answer 3

I found a solution after many tries. You can use a scope with param in your last has_many sentence in the User model:

has_many :comments, -> (user) {where organiser: user.organisers}, through: :participants

The "user" param represet the User object whom is calling the comments method.

Answer 4

Since we couldn't use has_many, through here because comments come from both of organizers and participants. I just think there are 2 solutions here:

Basically you can still change the foreign key to accept the self.id automatically with Rails here

User.first.comments

class User
  has_many :comments, -> { joins([{ organiser: :user }, { participant: :user }]) }, through: :participants, foreign_key: "users.id"
end

Answer 5

Could you do something as simple as:

has_many :comments, -> { joins(:participant, :organizer) }, class_name: 'Comment'

This should return all comments that have a Participant or Organizer User, since Rails tends to default joins to an inner join. You may not even need that :class_name argument.