Module | ActionView::Partials
In: | lib/action_view/partials.rb

There‘s also a convenience method for rendering sub templates within the current controller that depends on a single object (we call this kind of sub templates for partials). It relies on the fact that partials should follow the naming convention of being prefixed with an underscore — as to separate them from regular templates that could be rendered on their own.

In a template for Advertiser#account:

     <%= render :partial => "account" %>

This would render "advertiser/_account.rhtml" and pass the instance variable @account in as a local variable `account` to the template for display.

In another template for Advertiser#buy, we could have:

      <%= render :partial => "account", :locals => { :account => @buyer } %>

      <% for ad in @advertisements %>
        <%= render :partial => "ad", :locals => { :ad => ad } %>
      <% end %>

This would first render "advertiser/_account.rhtml" with @buyer passed in as the local variable `account`, then render "advertiser/_ad.rhtml" and pass the local variable `ad` to the template for display.

## Rendering a collection of partials

The example of partial use describes a familiar pattern where a template needs to iterate over an array and render a sub template for each of the elements. This pattern has been implemented as a single method that accepts an array and renders a partial by the same name as the elements contained within. So the three-lined example in "Using partials" can be rewritten with a single line:

      <%= render :partial => "ad", :collection => @advertisements %>

This will render "advertiser/_ad.rhtml" and pass the local variable `ad` to the template for display. An iteration counter will automatically be made available to the template with a name of the form `partial_name_counter`. In the case of the example above, the template would be fed `ad_counter`.

NOTE: Due to backwards compatibility concerns, the collection can‘t be one of hashes. Normally you‘d also just keep domain objects, like Active Records, in there.

## Rendering shared partials

Two controllers can share a set of partials and render them like this:

      <%= render :partial => "advertisement/ad", :locals => { :ad => @advertisement } %>

This will render the partial "advertisement/_ad.rhtml" regardless of which controller this is being called from.

### External Aliases

render_partial_collection | -> | render_collection_of_partials

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