title: instance and class variables in rails controller
body: <p>I'm new to rails and ruby. I was studying the concept of class and instance variables. I understood the difference but when I tried it out using the controller in rails it got me confused. What I did is I declared a class and instance variables outside the class methods:</p>
  
  <pre><code>class BooksController &lt; ApplicationController
    # GET /books
    # GET /books.json
  
    @@world = "Hello World"
    @insworld = "my hobby"
  
    def index
      @books = Book.all
      binding.pry
  
      respond_to do |format|
        format.html # index.html.erb
        format.json { render json: @books }
      end
    end
  
  end
  </code></pre>
  
  <p>I was under the impression that @insworld has the value of "my hobby", but when I tried to check the value of @insworld when I was inside the <code>index method</code>, @insworld was returning a nil value. @@world has the value of "Hello World". So what happened here? Aren't they defined in the same class?</p>