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", :account => @buyer %>
<% for ad in @advertisements %>
<%= render_partial "ad", :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_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 => @advertisement %>
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 45
45: def render_partial(partial_path, local_assigns = {}, deprecated_local_assigns = {})
46: path, partial_name = partial_pieces(partial_path)
47: object = extracting_object(partial_name, local_assigns, deprecated_local_assigns)
48: local_assigns = extract_local_assigns(local_assigns, deprecated_local_assigns)
49: add_counter_to_local_assigns!(partial_name, local_assigns)
50:
51: render("#{path}/_#{partial_name}", { partial_name => object }.merge(local_assigns))
52: end
[ show source ]
# File vendor/rails/actionpack/lib/action_view/partials.rb, line 54
54: def render_partial_collection(partial_name, collection, partial_spacer_template = nil, local_assigns = {})
55: collection_of_partials = Array.new
56: counter_name = partial_counter_name(partial_name)
57: collection.each_with_index do |element, counter|
58: collection_of_partials.push(render_partial(partial_name, element, { counter_name => counter }.merge(local_assigns)))
59: end
60:
61: return nil if collection_of_partials.empty?
62: if partial_spacer_template
63: spacer_path, spacer_name = partial_pieces(partial_spacer_template)
64: collection_of_partials.join(render("#{spacer_path}/_#{spacer_name}"))
65: else
66: collection_of_partials
67: end
68: end