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 the template for Advertiser#buy, we could have:
<% for ad in @advertisements %>
<%= render_partial "ad", ad %>
<% end %>
This would 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_collection "ad", @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.
Rendering shared partials
Two controllers can share a set of partials and render them like this:
<%= render_partial "advertisement/ad", ad %>
This will render the partial "advertisement/_ad.rhtml" regardless of which controller this is being called from.
Alias for render_partial_collection
[ show source ]
# File vendor/rails/actionpack/lib/action_view/partials.rb, line 34
34: def render_partial(partial_path, object = nil, local_assigns = {})
35: path, partial_name = partial_pieces(partial_path)
36: object ||= controller.instance_variable_get("@#{partial_name}")
37: counter_name = partial_counter_name(partial_name)
38: local_assigns = local_assigns.merge(counter_name => 1) unless local_assigns.has_key?(counter_name)
39: render("#{path}/_#{partial_name}", { partial_name => object }.merge(local_assigns))
40: end
[ show source ]
# File vendor/rails/actionpack/lib/action_view/partials.rb, line 42
42: def render_partial_collection(partial_name, collection, partial_spacer_template = nil, local_assigns = {})
43: collection_of_partials = Array.new
44: counter_name = partial_counter_name(partial_name)
45: collection.each_with_index do |element, counter|
46: collection_of_partials.push(render_partial(partial_name, element, { counter_name => counter }.merge(local_assigns)))
47: end
48:
49: return nil if collection_of_partials.empty?
50: if partial_spacer_template
51: spacer_path, spacer_name = partial_pieces(partial_spacer_template)
52: collection_of_partials.join(render("#{spacer_path}/_#{spacer_name}"))
53: else
54: collection_of_partials
55: end
56: end