undefined method `post_id' with post as a join table?

Question

Okay, so I am currently working on a commenting system where posts belong to classrooms and posts have comments. So classrooms have comments through posts.

Here are the models

class Classroom < ActiveRecord::Base
  has_many :posts
  has_many :comments, through: :posts
...
end
class Comment < ActiveRecord::Base
    belongs_to :post
...
end
class Post < ActiveRecord::Base
  belongs_to :classroom
  has_many :comments
...
end

I'm trying to save post_ids but it won't let me with a simple hidden field so I tried it with a value and it still doesn't work. it says that post_id is an undefined method.

Here is my classroom controller's show method because it is where the new comment form is being rendered.

def show
    @classroom = Classroom.find(params[:id])
    @posts = @classroom.posts
    @comments =  @classroom.comments
    @comment = Comment.new
  end

Here is the new comment form.

<%= simple_form_for(@comment) do |f| %>
  <%= f.error_notification %>

  <%= f.text_area :content %>

  <%= f.hidden_field :post_id, :value => @classroom.post_id  %>
  <div class="form-actions">
    <br>
    <%= f.button :submit %>
  </div>
<% end %>

Error Message NoMethodError in Classrooms#show undefined method `post_id' for Classroom:0x007f52aa646b18

How do I save the post_id? Thanks!

Answer 1

NoMethodError in Classrooms#show undefined method `post_id' for Classroom:0x007f52aa646b18

<%= f.hidden_field :post_id, :value => @classroom.post_id  %>

The error is obvious as you are doing @classroom.post_id as Classroom don't have a field called post_id

Define a @post with the help of @classroom

def show
  @classroom = Classroom.find(params[:id])
  @post = Post.where(classroom_id: @classroom.id).first
  @posts = @classroom.posts
  @comments =  @classroom.comments
  @comment = Comment.new
end

and use that in the hidden_field

<%= f.hidden_field :post_id, :value => @post.id %>