Question

A user can have many posts, and each post can have many comments. When visiting a user’s profile, you get a list of posts rendered like so in the view:

<%= render @posts %>

I want to also render the comments for each post by doing something like:

<%= render @comments %>

However, where would I declare @comments? If I declare it in user#show, then I’d get all the comments for the user, as opposed to the comments for a specific post.

So when a collection is rendered, does it access a controller for each instance? If so, what controller method is it using?

Answer 1

You can render each post’s comments inside the post partial:

<% @posts.each do |post| %>
  <%= render post %>
  <%= render :partial => 'posts_comments', :collection => post.comments %>
<% end %>

This does not go to the controller on each post.comments statement, it just queries the DB.

You can also eliminate the multiple queries by setting the @posts instance variable in the controller in the following way:

@posts = @user.posts.includes(:comments)

Then when you do post.comments it will not query the DB, but load the comments from the memory.