module ActionView
# 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.erb" 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.erb" with @buyer passed in as the local variable +account+, then
# render "advertiser/_ad.erb" 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.erb" 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.erb" regardless of which controller this is being called from.
#
# == Rendering objects with the RecordIdentifier
#
# Instead of explicitly naming the location of a partial, you can also let the RecordIdentifier do the work if
# you're following its conventions for RecordIdentifier#partial_path. Examples:
#
# # @account is an Account instance, so it uses the RecordIdentifier to replace
# # <%= render :partial => "accounts/account", :locals => { :account => @buyer } %>
# <%= render :partial => @account %>
#
# # @posts is an array of Post instances, so it uses the RecordIdentifier to replace
# # <%= render :partial => "posts/post", :collection => @posts %>
# <%= render :partial => @posts %>
#
# == Rendering the default case
#
# If you're not going to be using any of the options like collections or layouts, you can also use the short-hand
# defaults of render to render partials. Examples:
#
# # Instead of <%= render :partial => "account" %>
# <%= render "account" %>
#
# # Instead of <%= render :partial => "account", :locals => { :account => @buyer } %>
# <%= render "account", :account => @buyer %>
#
# # @account is an Account instance, so it uses the RecordIdentifier to replace
# # <%= render :partial => "accounts/account", :locals => { :account => @account } %>
# <%= render(@account) %>
#
# # @posts is an array of Post instances, so it uses the RecordIdentifier to replace
# # <%= render :partial => "posts/post", :collection => @posts %>
# <%= render(@posts) %>
#
# == Rendering partials with layouts
#
# Partials can have their own layouts applied to them. These layouts are different than the ones that are
# specified globally for the entire action, but they work in a similar fashion. Imagine a list with two types
# of users:
#
# <%# app/views/users/index.html.erb &>
# Here's the administrator:
# <%= render :partial => "user", :layout => "administrator", :locals => { :user => administrator } %>
#
# Here's the editor:
# <%= render :partial => "user", :layout => "editor", :locals => { :user => editor } %>
#
# <%# app/views/users/_user.html.erb &>
# Name: <%= user.name %>
#
# <%# app/views/users/_administrator.html.erb &>
# <div id="administrator">
# Budget: $<%= user.budget %>
# <%= yield %>
# </div>
#
# <%# app/views/users/_editor.html.erb &>
# <div id="editor">
# Deadline: <%= user.deadline %>
# <%= yield %>
# </div>
#
# ...this will return:
#
# Here's the administrator:
# <div id="administrator">
# Budget: $<%= user.budget %>
# Name: <%= user.name %>
# </div>
#
# Here's the editor:
# <div id="editor">
# Deadline: <%= user.deadline %>
# Name: <%= user.name %>
# </div>
#
# You can also apply a layout to a block within any template:
#
# <%# app/views/users/_chief.html.erb &>
# <% render(:layout => "administrator", :locals => { :user => chief }) do %>
# Title: <%= chief.title %>
# <% end %>
#
# ...this will return:
#
# <div id="administrator">
# Budget: $<%= user.budget %>
# Title: <%= chief.name %>
# </div>
#
# As you can see, the <tt>:locals</tt> hash is shared between both the partial and its layout.
#
# If you pass arguments to "yield" then this will be passed to the block. One way to use this is to pass
# an array to layout and treat it as an enumerable.
#
# <%# app/views/users/_user.html.erb &>
# <div class="user">
# Budget: $<%= user.budget %>
# <%= yield user %>
# </div>
#
# <%# app/views/users/index.html.erb &>
# <% render :layout => @users do |user| %>
# Title: <%= user.title %>
# <% end %>
#
# This will render the layout for each user and yield to the block, passing the user, each time.
#
# You can also yield multiple times in one layout and use block arguments to differentiate the sections.
#
# <%# app/views/users/_user.html.erb &>
# <div class="user">
# <%= yield user, :header %>
# Budget: $<%= user.budget %>
# <%= yield user, :footer %>
# </div>
#
# <%# app/views/users/index.html.erb &>
# <% render :layout => @users do |user, section| %>
# <%- case section when :header -%>
# Title: <%= user.title %>
# <%- when :footer -%>
# Deadline: <%= user.deadline %>
# <%- end -%>
# <% end %>
module Partials
extend ActiveSupport::Concern
class PartialRenderer
def self.partial_names
@partial_names ||= Hash.new {|h,k| h[k] = ActiveSupport::ConcurrentHash.new }
end
def self.formats
@formats ||= Hash.new {|h,k| h[k] = Hash.new{|h,k| h[k] = Hash.new {|h,k| h[k] = {}}}}
end
def initialize(view_context, options, block)
partial = options[:partial]
@view = view_context
@options = options
@locals = options[:locals] || {}
@block = block
# Set up some instance variables to speed up memoizing
@partial_names = self.class.partial_names[@view.controller.class]
@templates = self.class.formats
@format = view_context.formats
# Set up the object and path
@object = partial.is_a?(String) ? options[:object] : partial
@path = partial_path(partial)
end
def render
return render_collection if collection
template = find_template
render_template(template, @object || @locals[template.variable_name])
end
def render_collection
# Even if no template is rendered, this will ensure that the MIME type
# for the empty response is the same as the provided template
@options[:_template] = default_template = find_template
return nil if collection.blank?
if @options.key?(:spacer_template)
spacer = find_template(@options[:spacer_template]).render(@view, @locals)
end
segments = []
collection.each_with_index do |object, index|
template = default_template || find_template(partial_path(object))
@locals[template.counter_name] = index
segments << render_template(template, object)
end
segments.join(spacer)
end
def render_template(template, object = @object)
@options[:_template] ||= template
# TODO: is locals[:object] really necessary?
@locals[:object] = @locals[template.variable_name] = object
@locals[@options[:as]] = object if @options[:as]
content = @view._render_single_template(template, @locals, &@block)
return content if @block || !@options[:layout]
find_template(@options[:layout]).render(@view, @locals) { content }
end
private
def collection
@collection ||= if @object.respond_to?(:to_ary)
@object
elsif @options.key?(:collection)
@options[:collection] || []
end
end
def find_template(path = @path)
return if !path
@templates[path][@view.controller_path][@format][I18n.locale] ||= begin
prefix = @view.controller.controller_path unless path.include?(?/)
@view.find(path, {:formats => @view.formats}, prefix, true)
end
end
def partial_path(object = @object)
return object if object.is_a?(String)
@partial_names[object.class] ||= begin
return nil unless object.respond_to?(:to_model)
object.to_model.class.model_name.partial_path.dup.tap do |partial|
path = @view.controller_path
partial.insert(0, "#{File.dirname(path)}/") if path.include?(?/)
end
end
end
end
def render_partial(options)
@assigns_added = false
# TODO: Handle other details here.
self.formats = options[:_details][:formats] if options[:_details]
_render_partial(options)
end
def _render_partial(options, &block) #:nodoc:
PartialRenderer.new(self, options, block).render
end
end
end
