module AbstractController
# 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
#
# 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
#
# == Layout assignment
#
# You can either specify a layout declaratively (using the #layout class method) or give
# it the same name as your controller, and place it in <tt>app/views/layouts</tt>.
# If a subclass does not have a layout specified, it inherits its layout using normal Ruby inheritance.
#
# For instance, if you have PostsController and a template named <tt>app/views/layouts/posts.html.erb</tt>,
# that template will be used for all actions in PostsController and controllers inheriting
# from PostsController.
#
# If you use a module, for instance Weblog::PostsController, you will need a template named
# <tt>app/views/layouts/weblog/posts.html.erb</tt>.
#
# Since all your controllers inherit from ApplicationController, they will use
# <tt>app/views/layouts/application.html.erb</tt> if no other layout is specified
# or provided.
#
# == Inheritance Examples
#
# class BankController < ActionController::Base
# layout "bank_standard"
#
# class InformationController < BankController
#
# class TellerController < BankController
# # teller.html.erb exists
#
# class TillController < TellerController
#
# 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.
#
# The TellerController uses +teller.html.erb+, and TillController inherits that layout and
# uses it as well.
#
# == 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 be looked for in <tt>app/views/layouts/</tt>.
# Otherwise, it will be looked up relative to the template root.
#
# == 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.
# Sometimes you'll have exceptions where one action wants to use a different layout than the rest of the controller.
# You can do this by passing a <tt>:layout</tt> option to the <tt>render</tt> call. For example:
#
# class WeblogController < ActionController::Base
# layout "weblog_standard"
#
# def help
# render :action => "help", :layout => "help"
# end
# end
#
# This will render the help action with the "help" layout instead of the controller-wide "weblog_standard" layout.
module Layouts
extend ActiveSupport::Concern
include Rendering
included do
class_attribute :_layout_conditions
delegate :_layout_conditions, :to => :'self.class'
self._layout_conditions = {}
_write_layout_method
end
module ClassMethods
def inherited(klass)
super
klass._write_layout_method
end
# This module is mixed in if layout conditions are provided. This means
# that if no layout conditions are used, this method is not used
module LayoutConditions
# Determines whether the current action has a layout by checking the
# action name against the :only and :except conditions set on the
# layout.
#
# ==== Returns
# Boolean:: True if the action has a layout, false otherwise.
def _action_has_layout?
conditions = _layout_conditions
if only = conditions[:only]
only.include?(action_name)
elsif except = conditions[:except]
!except.include?(action_name)
else
true
end
end
end
# Specify the layout to use for this class.
#
# If the specified layout is a:
# String:: the String is the template name
# Symbol:: call the method specified by the symbol, which will return
# the template name
# false:: There is no layout
# true:: raise an ArgumentError
#
# ==== Parameters
# layout<String, Symbol, false)>:: The layout to use.
#
# ==== Options (conditions)
# :only<#to_s, Array[#to_s]>:: A list of actions to apply this layout to.
# :except<#to_s, Array[#to_s]>:: Apply this layout to all actions but this one
def layout(layout, conditions = {})
include LayoutConditions unless conditions.empty?
conditions.each {|k, v| conditions[k] = Array(v).map {|a| a.to_s} }
self._layout_conditions = conditions
@_layout = layout || false # Converts nil to false
_write_layout_method
end
# If no layout is supplied, look for a template named the return
# value of this method.
#
# ==== Returns
# String:: A template name
def _implied_layout_name
controller_path
end
# Takes the specified layout and creates a _layout method to be called
# by _default_layout
#
# If there is no explicit layout specified:
# If a layout is found in the view paths with the controller's
# name, return that string. Otherwise, use the superclass'
# layout (which might also be implied)
def _write_layout_method
case defined?(@_layout) ? @_layout : nil
when String
self.class_eval %{def _layout(details) #{@_layout.inspect} end}
when Symbol
self.class_eval <<-ruby_eval, __FILE__, __LINE__ + 1
def _layout(details)
#{@_layout}.tap do |layout|
unless layout.is_a?(String) || !layout
raise ArgumentError, "Your layout method :#{@_layout} returned \#{layout}. It " \
"should have returned a String, false, or nil"
end
end
end
ruby_eval
when Proc
define_method :_layout_from_proc, &@_layout
self.class_eval %{def _layout(details) _layout_from_proc(self) end}
when false
self.class_eval %{def _layout(details) end}
when true
raise ArgumentError, "Layouts must be specified as a String, Symbol, false, or nil"
when nil
if name
self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
def _layout(details)
if template_exists?("#{_implied_layout_name}", :_prefix => "layouts")
"#{_implied_layout_name}"
else
super
end
end
RUBY
end
end
self.class_eval { private :_layout }
end
end
def render_to_body(options = {})
# In the case of a partial with a layout, handle the layout
# here, and make sure the view does not try to handle it
layout = options.delete(:layout) if options.key?(:partial)
response = super
# This is a little bit messy. We need to explicitly handle partial
# layouts here since the core lookup logic is in the view, but
# we need to determine the layout based on the controller
#
# TODO: An easier way to handle this would probably be to override
# render_template
if layout
layout = _layout_for_option(layout, options[:_template].details)
response = layout.render(view_context, options[:locals] || {}) { response }
end
response
end
private
# This will be overwritten by _write_layout_method
def _layout(details) end
# Determine the layout for a given name and details.
#
# ==== Parameters
# name<String>:: The name of the template
# details<Hash{Symbol => Object}>:: A list of details to restrict
# the lookup to. By default, layout lookup is limited to the
# formats specified for the current request.
def _layout_for_name(name, details)
name && _find_layout(name, details)
end
# Determine the layout for a given name and details, taking into account
# the name type.
#
# ==== Parameters
# name<String|TrueClass|FalseClass|Symbol>:: The name of the template
# details<Hash{Symbol => Object}>:: A list of details to restrict
# the lookup to. By default, layout lookup is limited to the
# formats specified for the current request.
def _layout_for_option(name, details)
case name
when String then _layout_for_name(name, details)
when true then _default_layout(details, true)
when :default then _default_layout(details, false)
when false, nil then nil
else
raise ArgumentError,
"String, true, or false, expected for `layout'; you passed #{name.inspect}"
end
end
def _determine_template(options)
super
return unless (options.keys & [:text, :inline, :partial]).empty? || options.key?(:layout)
layout = options.key?(:layout) ? options[:layout] : :default
options[:_layout] = _layout_for_option(layout, options[:_template].details)
end
# Take in the name and details and find a Template.
#
# ==== Parameters
# name<String>:: The name of the template to retrieve
# details<Hash>:: A list of details to restrict the search by. This
# might include details like the format or locale of the template.
#
# ==== Returns
# Template:: A template object matching the name and details
def _find_layout(name, details)
prefix = details.key?(:prefix) ? details.delete(:prefix) : "layouts"
# TODO This should happen automatically
template_lookup.details = template_lookup.details.merge(:formats => details[:formats])
find_template(name, :_prefix => prefix)
end
# Returns the default layout for this controller and a given set of details.
# Optionally raises an exception if the layout could not be found.
#
# ==== Parameters
# details<Hash>:: A list of details to restrict the search by. This
# might include details like the format or locale of the template.
# require_layout<Boolean>:: If this is true, raise an ArgumentError
# with details about the fact that the exception could not be
# found (defaults to false)
#
# ==== Returns
# Template:: The template object for the default layout (or nil)
def _default_layout(details, require_layout = false)
if require_layout && _action_has_layout? && !_layout(details)
raise ArgumentError,
"There was no default layout for #{self.class} in #{view_paths.inspect}"
end
begin
_layout_for_name(_layout(details), details) if _action_has_layout?
rescue NameError => e
raise NoMethodError,
"You specified #{@_layout.inspect} as the layout, but no such method was found"
end
end
def _action_has_layout?
true
end
end
end
