Devise: binding 'resource' (aka general error reporting)

The much maligned but otherwise innocent "devise_error_messages!" method
in the DeviseHelper module starts out with:

def devise_error_messages!
    return "" if resource.errors.empty?
    ...
end

My question: where is 'resource' set up? I'd like to replicate its
functionality, but my naive approach (creating a FooHelper module in
app/helpers) fails because 'resource' isn't bound.

Another way to ask the question: rather than creating specific error
handlers for User, Topic, Profile, etc, I'd like to write a single error
handling helper that can be used for any model.

Right now each of my _form.html.erb files start with something like:

<% if @user.errors.any? %>
<div id="error_explanation">
  <h2><%= pluralize(@user.errors.count, "error") %> prohibited this user
from being saved:</h2>
  <ul>
    <% @user.errors.full_messages.each do |msg| %>
    <li><%= msg %></li>
    <% end %>
  </ul>
</div>
<% end %>

... but it's clearly unDRY to replicate that for @user, @topic,
@profile. How can I write a helper that will generalize to the current
resource?

- ff

P.S.: Anyone looking to eliminate the "DEPRECATION WARNING:
f.error_messages was removed from Rails" warning might be interested in
the answer to this thread. Now it will turn up in a search...

I figured out the answer to my own question, and I'm embarrassed by how
trivial it is: create a helper function that takes @user, @topic,
@profile etc as an argument. For example:

# app/helpers/my_helper.rb
module MyHelper
  def my_error_message(obj)
    return unless obj.errors.any?
    summary = "#{pluralize(obj.errors.count, "error")} prevented this
#{obj.class} from being saved:"
    msgs = obj.errors.full_messages.map { |msg| content_tag(:li, msg)
}.join
    "<div
id=\"error_explanation\"><h3>#{summary}</h3><ul>#{msgs}</ul></div>".html_safe
  end
end

Now you can sprinkle <%= my_error_message(@user) %> in the top of
user/_form.html.erb, etc. Works like a champ.

- ff

Much obliged for this answer!