Ruby on Rails 2.0: link_to for nested resources

If you specify nested resources in routes.rb such as

  map.resources :daily_contents do |daily_content|
    daily_content.resources :vocabularies   
  end

you have to specify a parameter for link_to like this:

  <% for vocabulary in @daily_content.vocabularies %>
    ..
    <%= link_to 'Show', [@daily_content, vocabulary] %>
  <% end %>

The generated URL is like this:

    http://localhost:3000/daily_contents/5/vocabularies/2

Moreover, if @daily_content.entities is just an array, which happens to contain an object of type, Vocabulary, the following works as well:

  <% for entity in @daily_content.entities %>
    ..
    <%= link_to 'Show', [@daily_content, entity] %>
  <% end %>

Again the generated URL is same as above like:

    http://localhost:3000/daily_contents/5/vocabularies/2