Question

What I am trying to do is the following:
Say we have a post that may have many questions and answers where both questions and answers belong to a given post. What I am trying to figure out is how to get the posts that have less than 5 questions and answers together.

something like:

@posts = Post.where(post.questions + post.answers < 5)

any suggestions?

Answer 1

You could create a new field on the table that would hold the sum of the questions and answers of a post. This could be done using a callback like this:

  class Post < ActiveRecord::Base
    ...

    # After you've created the sum field (migration etc.)
    before_save do |post|
      post.sum = post.questions.count + post.answers.count
    end
  end

Then in your controller you could do @posts = Post.where('sum < 5')