require 'active_support/core_ext/object/blank'
module ActionView
# = Action View Partials
#
# 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.
#
# == The :as and :object options
#
# By default <tt>ActionView::Partials::PartialRenderer</tt> has its object in a local variable with the same
# name as the template. So, given
#
# <%= render :partial => "contract" %>
#
# within contract we'll get <tt>@contract</tt> in the local variable +contract+, as if we had written
#
# <%= render :partial => "contract", :locals => { :contract => @contract } %>
#
# With the <tt>:as</tt> option we can specify a different name for said local variable. For example, if we
# wanted it to be +agreement+ instead of +contract+ we'd do:
#
# <%= render :partial => "contract", :as => :agreement %>
#
# The <tt>:object</tt> option can be used to directly specify which object is rendered into the partial;
# useful when the template's object is elsewhere, in a different ivar or in a local variable for instance.
#
# Revisiting a previous example we could have written this code:
#
# <%= render :partial => "account", :object => @buyer %>
#
# <% for ad in @advertisements %>
# <%= render :partial => "ad", :object => ad %>
# <% end %>
#
# The <tt>:object</tt> and <tt>:as</tt> options can be used together.
#
# == 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+.
#
# The <tt>:as</tt> option may be used when rendering partials.
#
# You can specify a partial to be rendered between elements via the <tt>:spacer_template</tt> option.
# The following example will render <tt>advertiser/_ad_divider.html.erb</tt> between each ad partial:
#
# <%= render :partial => "ad", :collection => @advertisements, :spacer_template => "ad_divider" %>
#
# If the given <tt>:collection</tt> is nil or empty, <tt>render</tt> will return nil. This will allow you
# to specify a text which will displayed instead by using this form:
#
# <%= render(:partial => "ad", :collection => @advertisements) || "There's no ad to be displayed" %>
#
# 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 => @account} %>
# <%= 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
def _render_partial(options, &block) #:nodoc:
_partial_renderer.setup(options, block).render
end
def _partial_renderer #:nodoc:
@_partial_renderer ||= PartialRenderer.new(self)
end
end
end
