title: helper method included in a model produces "undefined local variable or method `config' for" error
body: <p>I have a quite complex helper method that is also needed to be in a model. I've done it with just including some helpers in my model, but the same approach is not working on Rails 3.0.7.</p>
  
  <pre><code>module ContentsHelper
    def content_teaser record
      # it uses image_tag, truncate, raw, and some others.
    end
  end
  
  class Content &lt; ActiveRecord::Base
    include ActionView::Helpers::TagHelper
    include ActionView::Helpers::UrlHelper
    include ActionController::UrlFor
    include ActionView::Helpers::TextHelper
    include ActionView::Helpers::RawOutputHelper
    include ActionView::Helpers::AssetTagHelper
    include ContentsHelper
    include Rails.application.routes.url_helpers
  
    def teaser
      content_teaser self.body        
    end
  end
  </code></pre>
  
  <p>and the error information I have</p>
  
  <pre><code>undefined local variable or method `config' for #&lt;Content:0x10bac7248&gt;
  app/helpers/contents_helper.rb:8:in `content_teaser'
  app/models/content.rb:70:in `teaser'
  </code></pre>
  
  <p>any suggestion/advice?</p>