Rails 4: combining has_many :through association with polymorphic association

Question

In my Rails 4 app, I have the following models:

User
has_many :administrations
has_many :calendars, through: :administrations
has_many :comments
has_many :calendar_comments, through: :calendars, :source => :comments

Calendar
has_many :administrations
has_many :users, through: :administrations
has_many :posts
has_many :comments, through: posts
has_many :ads

Administration
belongs_to :user
belongs_to :calendar

Post
belongs_to :calendar
has_many :comments, as: :commentable

Ad
belongs_to :calendar
has_many :comments, as: :commentable

Comment
belongs_to :commentable, polymorphic: true
belongs_to :user

I need to access the comments that belong_to an ad from the calendar the ad belongs_to.

This is what I am trying to do in my Calendars#Index action:

@posts_comments = @user.calendar_comments.where(commentable_type: "Post").order("created_at DESC").limit(5)
@ads_comments = @user.calendar_comments.where(commentable_type: "Ad").order("created_at DESC").limit(5)

My first guess was to add has_many :comments, through: ads in the Calendar model:

Calendar
has_many :administrations
has_many :users, through: :administrations
has_many :posts
has_many :comments, through: posts
has_many : ads
has_many :comments, through: ads

But that cancels the effect of has_many :comments, through: posts and then I can no longer access the comments that belong_to an post from the calendar the post belongs_to.

Is there a way to make BOTH has_many :comments, through: posts AND has_many :comments, through: ads work?

—————

UPDATE: according to this article and that Stack Overflow question, the answer may lay in the use of source: and source_type:.

Not sure how to use those however.

—————

UPDATE 2: would the following code make any sense?

class Calendar < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :users, through: :administrations
  has_many :posts, dependent: :destroy
  has_many :commented_posts, through: :comments, source: :commentable, source_type: 'Post'
  has_many :ads, dependent: :destroy
  has_many :commented_ads, through: :comments, source: :commentable, source_type: 'Ad'

—————

UPDATE 3: when I try the above code, I get the following error message:

Could not find the source association(s) :comments in model Calendar. Try 'has_many :calendar_comments, :through => :calendars, :source => <name>'. Is it one of administrations, users, posts, commented_posts, ads, commented_ads, invites, or pokes?

I tried the following:

class Calendar < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :users, through: :administrations
  has_many :posts, dependent: :destroy
  has_many :calendar_comments, :through => :calendars, :source => :post
  has_many :ads, dependent: :destroy
  has_many :calendar_comments, :through => :calendars, :source => :ad

—————

UPDATE 4: a new failed attempt with the following code:

class Calendar < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :users, through: :administrations
  has_many :posts, dependent: :destroy
  has_many :calendar_comments, :through => :commentable, :source => :post
  has_many :ads, dependent: :destroy
  has_many :calendar_comments, :through => :commentable, :source => :ad

Still not working, same error message as above.

—————

UPDATE 5: based on MrYoshiji's answer, I now have

class Calendar < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :users, through: :administrations
  has_many :posts, dependent: :destroy
  has_many :posts_comments, through: :posts, source_type: 'Post'
  has_many :ads, dependent: :destroy
  has_many :ads_comments, through: :ads, source_type: 'Ad'

Now, has_many :calendar_comments, through: :calendars, :source => :comments in the User model is no longer working.

I tried:

has_many :comments
has_many :calendar_post_comments, through: :calendars, :source => :post_comments
has_many :calendar_ad_comments, through: :calendars, :source => :ad_comments

Still not working.

—————

UPDATE 6: I am still stuck with this issue, since I cannot figure out a way to get the following code working:

@posts_comments = @user.calendar_comments.where(commentable_type: "Post").order("created_at DESC").limit(5)
@ads_comments = @user.calendar_comments.where(commentable_type: "Ad").order("created_at DESC").limit(5)

I tried many different things, and the best I could come up with so far was:

class Calendar < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :users, through: :administrations
  has_many :posts, dependent: :destroy
  has_many :post_comments, through: :posts, source_type: 'Post'
  has_many :ads, dependent: :destroy
  has_many :ad_comments, through: :ads, source_type: 'Ad'
end

class User < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :calendars, through: :administrations
  has_many :comments
  has_many :calendar_post_comments, through: :calendars, :source => :post_comments
  has_many :calendar_ad_comments, through: :calendars, :source => :ad_comments
end

Then, I update my Calendars controller as follows:

def index
    @user = current_user
    @calendars = @user.calendars.all
    @posts_comments = @user.calendar_post_comments
                              .order("created_at DESC")
                              .limit(5)
    @ads_comments = @user.calendar_ad.comments
                              .order("created_at DESC")
                              .limit(5)
end

But this returns the following error:

NoMethodError at /calendars
undefined method `chain' for nil:NilClass
@posts_comments = @user.calendar_post_comments.order("created_at DESC").limit(5)

What is wrong here?

Answer 1

You should try the following:

class Calendar < ActiveRecord::Base
  # [ ... ]
  has_many :posts
  has_many :posts_comments, through: posts, source_type: 'Post'
  has_many :ads
  has_many :ads_comments, through: ads, source_type: 'Ad'

Considering that Ad and Post models both have the following:

has_many :comments, as: :commentable