# frozen_string_literal: true
require "action_view/renderer/partial_renderer/collection_caching"
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.html.erb".
#
# In another template for Advertiser#buy, we could have:
#
# <%= render partial: "account", locals: { account: @buyer } %>
#
# <% @advertisements.each do |ad| %>
# <%= render partial: "ad", locals: { ad: ad } %>
# <% end %>
#
# This would first render <tt>advertiser/_account.html.erb</tt> with <tt>@buyer</tt> passed in as the local variable +account+, then
# render <tt>advertiser/_ad.html.erb</tt> and pass the local variable +ad+ to the template for display.
#
# == The +:as+ and +:object+ options
#
# By default ActionView::PartialRenderer doesn't have any local variables.
# The <tt>:object</tt> option can be used to pass an object to the partial. For instance:
#
# <%= render partial: "account", object: @buyer %>
#
# would provide the <tt>@buyer</tt> object to the partial, available under the local variable +account+ and is
# equivalent to:
#
# <%= render partial: "account", locals: { account: @buyer } %>
#
# With the <tt>:as</tt> option we can specify a different name for said local variable. For example, if we
# wanted it to be +user+ instead of +account+ we'd do:
#
# <%= render partial: "account", object: @buyer, as: 'user' %>
#
# This is equivalent to
#
# <%= render partial: "account", locals: { user: @buyer } %>
#
# == \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 <tt>advertiser/_ad.html.erb</tt> and pass the local variable +ad+ to the template for display. An
# iteration object will automatically be made available to the template with a name of the form
# +partial_name_iteration+. The iteration object has knowledge about which index the current object has in
# the collection and the total size of the collection. The iteration object also has two convenience methods,
# +first?+ and +last?+. In the case of the example above, the template would be fed +ad_iteration+.
# For backwards compatibility the +partial_name_counter+ is still present and is mapped to the iteration's
# +index+ method.
#
# 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 be displayed instead by using this form:
#
# <%= render(partial: "ad", collection: @advertisements) || "There's no ad to be displayed" %>
#
# == \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 <tt>advertisement/_ad.html.erb</tt> regardless of which controller this is being called from.
#
# == \Rendering objects that respond to +to_partial_path+
#
# Instead of explicitly naming the location of a partial, you can also let PartialRenderer do the work
# and pick the proper path by checking +to_partial_path+ method.
#
# # @account.to_partial_path returns 'accounts/account', so it can be used to replace:
# # <%= render partial: "accounts/account", locals: { account: @account} %>
# <%= render partial: @account %>
#
# # @posts is an array of Post instances, so every post record returns 'posts/post' on +to_partial_path+,
# # that's why we can 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.to_partial_path returns 'accounts/account', so it can be used to replace:
# # <%= render partial: "accounts/account", locals: { account: @account} %>
# <%= render @account %>
#
# # @posts is an array of Post instances, so every post record returns 'posts/post' on +to_partial_path+,
# # that's why we can 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>
#
# If a collection is given, the layout will be rendered once for each item in
# the collection. For example, these two snippets have the same output:
#
# <%# app/views/users/_user.html.erb %>
# Name: <%= user.name %>
#
# <%# app/views/users/index.html.erb %>
# <%# This does not use layouts %>
# <ul>
# <% users.each do |user| -%>
# <li>
# <%= render partial: "user", locals: { user: user } %>
# </li>
# <% end -%>
# </ul>
#
# <%# app/views/users/_li_layout.html.erb %>
# <li>
# <%= yield %>
# </li>
#
# <%# app/views/users/index.html.erb %>
# <ul>
# <%= render partial: "user", layout: "li_layout", collection: users %>
# </ul>
#
# Given two users whose names are Alice and Bob, these snippets return:
#
# <ul>
# <li>
# Name: Alice
# </li>
# <li>
# Name: Bob
# </li>
# </ul>
#
# The current object being rendered, as well as the object_counter, will be
# available as local variables inside the layout template under the same names
# as available in the partial.
#
# 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.
class PartialRenderer < AbstractRenderer
include CollectionCaching
def initialize(lookup_context, options)
super(lookup_context)
@options = options
@locals = @options[:locals] || {}
@details = extract_details(@options)
end
def render(partial, context, block)
template = find_template(partial, template_keys(partial))
if !block && (layout = @options[:layout])
layout = find_template(layout.to_s, template_keys(partial))
end
render_partial_template(context, @locals, template, layout, block)
end
private
def template_keys(_)
@locals.keys
end
def render_partial_template(view, locals, template, layout, block)
ActiveSupport::Notifications.instrument(
"render_partial.action_view",
identifier: template.identifier,
layout: layout && layout.virtual_path,
locals: locals
) do |payload|
content = template.render(view, locals, add_to_stack: !block) do |*name|
view._layout_for(*name, &block)
end
content = layout.render(view, locals) { content } if layout
payload[:cache_hit] = view.view_renderer.cache_hits[template.virtual_path]
build_rendered_template(content, template)
end
end
def find_template(path, locals)
prefixes = path.include?(?/) ? [] : @lookup_context.prefixes
@lookup_context.find_template(path, prefixes, true, locals, @details)
end
end
end