No instance variables in Rails controllers

gistfile1.rb

class PostsController < ActiveRecord::Base
  helper_method :posts, :post

  def index; end

  def create
    if post.save
    end
  end

  private

  def posts
    @posts ||= Post.all
  end

  def post
    @post ||= Post.new(params[:post] || {})
  end
end