Rails Error - undefined local variable or method `signout_path' - ruby-on-rails

Question

The error is from app/views/layouts/_header.html.erb. That piece of line is part of my app/views/layouts/_header.html.erb whic is the following:
<header class="navbar navbar-fixed-top navbar-inverse">
<div class="navbar-inner">
<div class="container">
<%= link_to "sample app", root_path, id: "logo" %>
<nav>
<ul class="nav pull-right">
<li><%= link_to "Home", root_path %></li>
<li><%= link_to "Help", help_path %></li>
<% if signed_in? %>
<li><%= link_to "Users", '#' %></li>
<li id="fat-menu" class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">
Account <b class="caret"></b>
</a>
<ul class="dropdown-menu">
<li><%= link_to "Profile", current_user %></li>
<li><%= link_to "Settings", '#' %></li>
<li class="divider"></li>
<li>
<%= link_to "Sign out", signout_path, method: "delete" %>
</li>
</ul>
</li>
<% else %>
<li><%= link_to "Sign in", signin_path %></li>
<% end %>
</ul>
</nav>
</div>
</div>
</header>

Answer 1

Ok, it's getting late here and i don't wait for your output of rake routes or routes.rb file.
As mentioned in my comment, got to your shell, cd to your application directory and run
rake routes
this will display all possible routes. Chances are, that there's already a route for the sign out process.
If not, you have to create the route in your /config/routes.rb and direct it to the right controller. For example
delete '/logout', to: 'sessions#destroy', as: 'signout'
where 'delete' is the request, '/logout' my example url, 'sessions' the controller and 'destroy' it's action and 'signout' your method name (as you wished it in your code).
you can just write
delete '/logout', to: 'sessions#destroy'
in this case, you have to replace your method-name signout_path for example with the url.
One last hint: Logging out can be done, too with GET instead of DELETE. Maybe you created a route with only the GET method? Should be obvious in the output of rake routes, too.