Action Controller Error: undefined local variable or method `current_user'

Newbie learning Rails. I'm currently on Chp9 here:
http://railstutorial.org/chapters/sign-in-sign-out#top

At the end of the tutorial, rails is erroring (see below). being new
to Rails and after having checked the tutorial... How do you resolve
this kind of error. It's saying current_user is not defined, and it is
supposed to be defined with/Sites/sample_app/app/helpers/
sessions_helper.rb

NameError in Pages#home

Showing /Users/iamme/Sites/sample_app/app/views/layouts/
_header.html.erb where line #6 raised:

undefined local variable or method `current_user' for #<#<Class:
0x103371258>:0x10336be70>
Extracted source (around line #6):

3: <nav class="round">
4: <ul>
5: <li><%= link_to "Home", root_path %></li>
6: <% if signed_in? %>
7: <li><%= link_to "Profile", current_user %></li>
8: <% end %>
9: <li><%= link_to "Help", help_path %></li>
Trace of template inclusion: app/views/layouts/application.html.erb

Rails.root: /Users/iamme/Sites/sample_app

Application Trace | Framework Trace | Full Trace
app/helpers/sessions_helper.rb:13:in `signed_in?'
app/views/layouts/_header.html.erb:6:in
`_app_views_layouts__header_html_erb___1701013666_2174344740_524030'
app/views/layouts/application.html.erb:10:in
`_app_views_layouts_application_html_erb__1439570095_2174436720_0'

---- END

sessions_helper.rb CODE:

module SessionsHelper

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

  def current_user=(user)
    @current_user = user
  end

  def signed_in?
    !current_user.nil?
  end

  def sign_out
    cookies.delete(:remember_token)
    self.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

--- END

thanks

Ok figured it out, the sessions_helper.rb needs to look like this:

module SessionsHelper

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

  def current_user=(user)
    @current_user = user
  end

  def current_user
    @current_user ||= user_from_remember_token
  end

  def signed_in?
    !current_user.nil?
  end

  def sign_out
    cookies.delete(:remember_token)
    self.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