Hello I get stuck at this point,

If anyone else runs into this problem and wants to continue using Rails 4 for this tutorial, i've posted a quick workaround on how to use Devise and add extra fields using Strong Parameters in Rails 4.

1. Ignore everything in this Treebook tutorial that has to do with attr_accessible. You can ignore all of those steps until you reach the 'Customizing Forms' section of this Treebook tutorial.

2. Once you reach the 'Customizing Forms' section of this Treebook tutorial, open this tutorial: http://www.jacopretorius.net/2014/03/adding-custom-fields-to-your-devise-user-model-in-rails-4.html

3. Skip ahead in this new tutorial to "Customizing the RegistrationsController," because we already did the first few steps before reaching the 'Customizing Forms' section in the Treebook tutorial.

4. Following along in this new short tutorial, go to Sublime Text and open up the controllers folder. Create a new ruby file in controllers called: registrations_controller.rb

5. Copy and paste the following into the registrations_controller.rb file that you created:

class RegistrationsController < Devise::RegistrationsController

  private

  def sign_up_params
    params.require(:user).permit(:first_name, :last_name, :profile_name, :email, :password, :password_confirmation)
  end

  def account_update_params
    params.require(:user).permit( :email, :password, :password_confirmation, :current_password)
  end
end

6: Then, go to the config folder in Sublime text and open the routes.rb file. Delete the devise_for :users line and replace it with the following:

 devise_for :users, :controllers => { registrations: 'registrations' }

1. Then, go to your statuses_controller.rb file and, at the very bottom, find this:

# Never trust parameters from the scary internet, only allow the white list through.
    def status_params
      params.require(:status).permit(:name, :content)
    end 

and change it to this:

# Never trust parameters from the scary internet, only allow the white list through.
    def status_params
      params.require(:status).permit(:user_id, :content)
    end 

You are all set! All of your parameters within your form should now be passed to the database when a new user signs up. You can continue forward in the Treebook tutorial.

Which version of Rails?

4.1.4

Thanks Maciej I'm going to switch to Rails 3.

I am using Rails 4. This is how I fixed my issue. While posting a new status don't select the random user_id like (1,2,34....etc). First open your console and see what is your user_id. Let us say, your user_id 3, keep that in mind!. Now while posting a new status always make sure you only select the user_id as 3 only. If you select any other user_id it will throw you nill class error for first_name. Because when you call @status.user.first_name, here the user does not exist if you select the user_id other than 3. Only user_id 3 exists. So if you call first_name on any user other than 3 it will throw you an error which clearly says "You're calling first_name on nill class which is User."