===VIEW===

      <%- form_for @credential, user_external_credentials_path(@user), :class => "horizontal" do -%>
        <div class="input-wrapper">
          <%= f.label :login, "Twitter Username" -%>
          <%= f.text_field :login, :class => 'text' -%>
        </div>

        <div class="input-wrapper">
          <%= f.label :password, "Twitter Password" -%>
          <%= f.password_field :password, :class => 'text' -%>
        </div>
    
        <div class="btn-wrapper">
          <%= f.submit "Save", :class => "button" %>
        </div>
      <%- end -%>
    <%- end -%>

=== CONTROLLER ===

  def sharing
    @credential = @user.external_credentials.new
  end

=== ERROR ===

ActionView::TemplateError (undefined method `external_credentials_path' for #<ActionView::Base:0x102f76e0>) on line #8 of app/views/users/sharing.html.erb:
5:     <%- if @user.twitter_credential.present? -%>
6:       Your Twitter credentials have been stored for username <strong><%= @user.twitter_credential.login %></strong>.
7:     <%- else -%>
8:       <%- form_for @credential, user_external_credentials_path(@user) do -%>
9:         <div class="input-wrapper">
10:           <%= f.label :login, "Twitter Username" -%>
11:           <%= f.text_field :login, :class => 'text' -%>

    vendor/rails/actionpack/lib/action_controller/polymorphic_routes.rb:109:in `__send__'
    vendor/rails/actionpack/lib/action_controller/polymorphic_routes.rb:109:in `polymorphic_url'
    vendor/rails/actionpack/lib/action_controller/polymorphic_routes.rb:116:in `polymorphic_path'
    vendor/rails/actionpack/lib/action_view/helpers/form_helper.rb:298:in `apply_form_for_options!'
    vendor/rails/actionpack/lib/action_view/helpers/form_helper.rb:277:in `form_for_without_haml'
    vendor/gems/haml-edge-2.1.13/rails/./lib/haml/helpers/action_view_mods.rb:171:in `form_for'
    app/views/users/sharing.html.erb:8