module ActionController #:nodoc:
module Layout #:nodoc:
def self.included(base)
base.extend(ClassMethods)
base.class_eval do
# NOTE: Can't use alias_method_chain here because +render_without_layout+ is already
# defined as a publicly exposed method
alias_method :render_with_no_layout, :render
alias_method :render, :render_with_a_layout
class << self
alias_method_chain :inherited, :layout
end
end
end
# Layouts reverse the common pattern of including shared headers and footers in many templates to isolate changes in
# repeated setups. The inclusion pattern has pages that look like this:
#
# <%= render "shared/header" %>
# Hello World
# <%= render "shared/footer" %>
#
# This approach is a decent way of keeping common structures isolated from the changing content, but it's verbose
# and if you ever want to change the structure of these two includes, you'll have to change all the templates.
#
# With layouts, you can flip it around and have the common structure know where to insert changing content. This means
# that the header and footer are only mentioned in one place, like this:
#
# // The header part of this layout
# <%= yield %>
# // The footer part of this layout -->
#
# And then you have content pages that look like this:
#
# hello world
#
# Not a word about common structures. At rendering time, the content page is computed and then inserted in the layout,
# like this:
#
# // The header part of this layout
# hello world
# // The footer part of this layout -->
#
# == Accessing shared variables
#
# Layouts have access to variables specified in the content pages and vice versa. This allows you to have layouts with
# references that won't materialize before rendering time:
#
# <h1><%= @page_title %></h1>
# <%= yield %>
#
# ...and content pages that fulfill these references _at_ rendering time:
#
# <% @page_title = "Welcome" %>
# Off-world colonies offers you a chance to start a new life
#
# The result after rendering is:
#
# <h1>Welcome</h1>
# Off-world colonies offers you a chance to start a new life
#
# == Automatic layout assignment
#
# If there is a template in <tt>app/views/layouts/</tt> with the same name as the current controller then it will be automatically
# set as that controller's layout unless explicitly told otherwise. Say you have a WeblogController, for example. If a template named
# <tt>app/views/layouts/weblog.erb</tt> or <tt>app/views/layouts/weblog.builder</tt> exists then it will be automatically set as
# the layout for your WeblogController. You can create a layout with the name <tt>application.erb</tt> or <tt>application.builder</tt>
# and this will be set as the default controller if there is no layout with the same name as the current controller and there is
# no layout explicitly assigned with the +layout+ method. Nested controllers use the same folder structure for automatic layout.
# assignment. So an Admin::WeblogController will look for a template named <tt>app/views/layouts/admin/weblog.erb</tt>.
# Setting a layout explicitly will always override the automatic behaviour for the controller where the layout is set.
# Explicitly setting the layout in a parent class, though, will not override the child class's layout assignement if the child
# class has a layout with the same name.
#
# == Inheritance for layouts
#
# Layouts are shared downwards in the inheritance hierarchy, but not upwards. Examples:
#
# class BankController < ActionController::Base
# layout "bank_standard"
#
# class InformationController < BankController
#
# class VaultController < BankController
# layout :access_level_layout
#
# class EmployeeController < BankController
# layout nil
#
# The InformationController uses "bank_standard" inherited from the BankController, the VaultController overwrites
# and picks the layout dynamically, and the EmployeeController doesn't want to use a layout at all.
#
# == Types of layouts
#
# Layouts are basically just regular templates, but the name of this template needs not be specified statically. Sometimes
# you want to alternate layouts depending on runtime information, such as whether someone is logged in or not. This can
# be done either by specifying a method reference as a symbol or using an inline method (as a proc).
#
# The method reference is the preferred approach to variable layouts and is used like this:
#
# class WeblogController < ActionController::Base
# layout :writers_and_readers
#
# def index
# # fetching posts
# end
#
# private
# def writers_and_readers
# logged_in? ? "writer_layout" : "reader_layout"
# end
#
# Now when a new request for the index action is processed, the layout will vary depending on whether the person accessing
# is logged in or not.
#
# If you want to use an inline method, such as a proc, do something like this:
#
# class WeblogController < ActionController::Base
# layout proc{ |controller| controller.logged_in? ? "writer_layout" : "reader_layout" }
#
# Of course, the most common way of specifying a layout is still just as a plain template name:
#
# class WeblogController < ActionController::Base
# layout "weblog_standard"
#
# If no directory is specified for the template name, the template will by default by looked for in +app/views/layouts/+.
#
# == Conditional layouts
#
# If you have a layout that by default is applied to all the actions of a controller, you still have the option of rendering
# a given action or set of actions without a layout, or restricting a layout to only a single action or a set of actions. The
# <tt>:only</tt> and <tt>:except</tt> options can be passed to the layout call. For example:
#
# class WeblogController < ActionController::Base
# layout "weblog_standard", :except => :rss
#
# # ...
#
# end
#
# This will assign "weblog_standard" as the WeblogController's layout except for the +rss+ action, which will not wrap a layout
# around the rendered view.
#
# Both the <tt>:only</tt> and <tt>:except</tt> condition can accept an arbitrary number of method references, so
# #<tt>:except => [ :rss, :text_only ]</tt> is valid, as is <tt>:except => :rss</tt>.
#
# == Using a different layout in the action render call
#
# If most of your actions use the same layout, it makes perfect sense to define a controller-wide layout as described above.
# Some times you'll have exceptions, though, where one action wants to use a different layout than the rest of the controller.
# This is possible using the <tt>render</tt> method. It's just a bit more manual work as you'll have to supply fully
# qualified template and layout names as this example shows:
#
# class WeblogController < ActionController::Base
# def help
# render :action => "help/index", :layout => "help"
# end
# end
#
# As you can see, you pass the template as the first parameter, the status code as the second ("200" is OK), and the layout
# as the third.
#
# NOTE: The old notation for rendering the view from a layout was to expose the magic <tt>@content_for_layout</tt> instance
# variable. The preferred notation now is to use <tt>yield</tt>, as documented above.
module ClassMethods
# If a layout is specified, all rendered actions will have their result rendered
# when the layout<tt>yield</tt>'s. This layout can itself depend on instance variables assigned during action
# performance and have access to them as any normal template would.
def layout(template_name, conditions = {})
add_layout_conditions(conditions)
write_inheritable_attribute "layout", template_name
end
def layout_conditions #:nodoc:
@layout_conditions ||= read_inheritable_attribute("layout_conditions")
end
def default_layout #:nodoc:
@default_layout ||= read_inheritable_attribute("layout")
end
def layout_list #:nodoc:
view_paths.collect do |path|
Dir["#{path}/layouts/**/*"]
end.flatten
end
private
def inherited_with_layout(child)
inherited_without_layout(child)
layout_match = child.name.underscore.sub(/_controller$/, '').sub(/^controllers\//, '')
child.layout(layout_match) unless child.layout_list.grep(%r{layouts/#{layout_match}(\.[a-z][0-9a-z]*)+$}).empty?
end
def add_layout_conditions(conditions)
write_inheritable_hash "layout_conditions", normalize_conditions(conditions)
end
def normalize_conditions(conditions)
conditions.inject({}) {|hash, (key, value)| hash.merge(key => [value].flatten.map {|action| action.to_s})}
end
def layout_directory_exists_cache
@@layout_directory_exists_cache ||= Hash.new do |h, dirname|
h[dirname] = File.directory? dirname
end
end
end
# Returns the name of the active layout. If the layout was specified as a method reference (through a symbol), this method
# is called and the return value is used. Likewise if the layout was specified as an inline method (through a proc or method
# object). If the layout was defined without a directory, layouts is assumed. So <tt>layout "weblog/standard"</tt> will return
# weblog/standard, but <tt>layout "standard"</tt> will return layouts/standard.
def active_layout(passed_layout = nil)
layout = passed_layout || self.class.default_layout
active_layout = case layout
when String then layout
when Symbol then send(layout)
when Proc then layout.call(self)
end
# Explicitly passed layout names with slashes are looked up relative to the template root,
# but auto-discovered layouts derived from a nested controller will contain a slash, though be relative
# to the 'layouts' directory so we have to check the file system to infer which case the layout name came from.
if active_layout
if active_layout.include?('/') && ! layout_directory?(active_layout)
active_layout
else
"layouts/#{active_layout}"
end
end
end
protected
def render_with_a_layout(options = nil, deprecated_status = nil, deprecated_layout = nil, &block) #:nodoc:
template_with_options = options.is_a?(Hash)
if apply_layout?(template_with_options, options) && (layout = pick_layout(template_with_options, options, deprecated_layout))
assert_existence_of_template_file(layout)
options = options.merge :layout => false if template_with_options
logger.info("Rendering template within #{layout}") if logger
if template_with_options
content_for_layout = render_with_no_layout(options, &block)
deprecated_status = options[:status] || deprecated_status
else
content_for_layout = render_with_no_layout(options, deprecated_status, &block)
end
erase_render_results
add_variables_to_assigns
@template.instance_variable_set("@content_for_layout", content_for_layout)
response.layout = layout
render_text(@template.render_file(layout, true), deprecated_status)
else
render_with_no_layout(options, deprecated_status, &block)
end
end
private
def apply_layout?(template_with_options, options)
return false if options == :update
template_with_options ? candidate_for_layout?(options) : !template_exempt_from_layout?
end
def candidate_for_layout?(options)
(options.has_key?(:layout) && options[:layout] != false) ||
options.values_at(:text, :xml, :json, :file, :inline, :partial, :nothing).compact.empty? &&
!template_exempt_from_layout?(default_template_name(options[:action] || options[:template]))
end
def pick_layout(template_with_options, options, deprecated_layout)
if deprecated_layout
deprecated_layout
elsif template_with_options
case layout = options[:layout]
when FalseClass
nil
when NilClass, TrueClass
active_layout if action_has_layout?
else
active_layout(layout)
end
else
active_layout if action_has_layout?
end
end
def action_has_layout?
if conditions = self.class.layout_conditions
case
when only = conditions[:only]
only.include?(action_name)
when except = conditions[:except]
!except.include?(action_name)
else
true
end
else
true
end
end
# Does a layout directory for this class exist?
# we cache this info in a class level hash
def layout_directory?(layout_name)
view_paths.find do |path|
File.file?(File.join(path, 'layouts', layout_name))
end
template_path ||= File.join(view_paths.first, 'layouts', layout_name)
dirname = File.dirname(template_path)
self.class.send(:layout_directory_exists_cache)[dirname]
end
end
end
