undefined local variable or method 'current_user'

Question

I'm currently going through a RoR tutorial (http://railstutorial.org/chapters/sign-in-sign-out#sec:signin_success is the relevant section) which seems to be fairly good, although I've run into the following problem when trying to view the sample site.

Extracted source (around line #10):

7:          <li><%= link_to "Home", root_path %></li>
8:          <li><%= link_to "About", about_path %></li>
9:          
10:             <% if signed_in? %>
11:                 <li><%= link_to "Profile", current_user %></li>
12:                 <li><%= link_to "Sign out", signout_path, :method => delete %></li>
13:             <% else %>

As you can see, the issue is stemming from my method "signed_in?" which is supposed to check if the user has logged in or not by checking whether the current_user variable is set (I've included the rest of the code from the helper to give a context, apologies):

module SessionsHelper

  def sign_in(user)
    cookies.permanent.signed[:remember_token] = [user.id, user.salt]
    current_user = user
  end

  def sign_out
    cookies.delete[:remember_token]
    current_user = nil
  end

  def current_user= (user)
    @current_user ||= user_from_remember_token
  end

  def signed_in?
    !current_user.nil?
  end

  private

    def user_from_remember_token
      User.authenticate_with_salt(*remember_token)
    end

    def remember_token
      cookies.signed[:remember_token] || [nil, nil]
    end

end

From my understanding, .nil? is a method that checks whether or not an object has been defined and therefore the object being undefined shouldn't generate an error but rather return false? I searched the tutorial for all cases of current_user (before checking to see if anyone else had this problem with little success) and my code seems correct so I'm a little confused and if anyone is able to help me understand the way Ruby variables are supposed to be accessed and why my code isn't working I'd be most grateful.

Edit:

I'm not sure if it's important with scope as I'm just beginning both Rails and Ruby, however the helper SessionsHelper is being used by my Users controller and views (it's included in my Applications controller)

Answer 1

I ran in to this same issue & it was for the same reason. You overlooked part of the instructions on 'Listing 9.16'.

def current_user= (user)
  @current_user ||= user_from_remember_token
end

You were supposed to change this to the following.

def current_user
  @current_user ||= user_from_remember_token
end

You'll also want to change all of the instances of *self.*current_user to *@*current_user.

Once you do this the error(s) are resolved.