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require "active_support/core_ext/module/remove_method"
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" }
# end
#
# 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"
# end
#
# 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
# * <tt> Boolean</tt> - True if the action has a layout, false otherwise.
def action_has_layout?
return unless super
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
# * <tt>String, Symbol, false</tt> - The layout to use.
#
# ==== Options (conditions)
# * :only - A list of actions to apply this layout to.
# * :except - 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
# * <tt>String</tt> - A template name
def _implied_layout_name
controller_path
end
# Creates a _layout method to be called by _default_layout .
#
# If a layout is not explicitly mentioned then look for a layout with the controller's name.
# if nothing is found then try same procedure to find super class's layout.
def _write_layout_method
remove_possible_method(:_layout)
case defined?(@_layout) ? @_layout : nil
when String
self.class_eval %{def _layout; #{@_layout.inspect} end}, __FILE__, __LINE__
when Symbol
self.class_eval <<-ruby_eval, __FILE__, __LINE__ + 1
def _layout
#{@_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; _layout_from_proc(self) end}, __FILE__, __LINE__
when false
self.class_eval %{def _layout; end}, __FILE__, __LINE__
when true
raise ArgumentError, "Layouts must be specified as a String, Symbol, false, or nil"
when nil
if name
_prefixes = _implied_layout_name =~ /\blayouts/ ? [] : ["layouts"]
self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
def _layout
if template_exists?("#{_implied_layout_name}", #{_prefixes.inspect})
"#{_implied_layout_name}"
else
super
end
end
RUBY
end
end
self.class_eval { private :_layout }
end
end
def _normalize_options(options)
super
if _include_layout?(options)
layout = options.key?(:layout) ? options.delete(:layout) : :default
value = _layout_for_option(layout)
options[:layout] = (value =~ /\blayouts/ ? value : "layouts/#{value}") if value
end
end
attr_writer :action_has_layout
def initialize(*)
@action_has_layout = true
super
end
def action_has_layout?
@action_has_layout
end
private
# This will be overwritten by _write_layout_method
def _layout; end
# Determine the layout for a given name and details, taking into account
# the name type.
#
# ==== Parameters
# * <tt>name</tt> - The name of the template
# * <tt>details</tt> - 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)
case name
when String then name
when true then _default_layout(true)
when :default then _default_layout(false)
when false, nil then nil
else
raise ArgumentError,
"String, true, or false, expected for `layout'; you passed #{name.inspect}"
end
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
# * <tt>details</tt> - A list of details to restrict the search by. This
# might include details like the format or locale of the template.
# * <tt>require_layout</tt> - If this is true, raise an ArgumentError
# with details about the fact that the exception could not be
# found (defaults to false)
#
# ==== Returns
# * <tt>template</tt> - The template object for the default layout (or nil)
def _default_layout(require_layout = false)
begin
layout_name = _layout if action_has_layout?
rescue NameError => e
raise e, "Could not render layout: #{e.message}"
end
if require_layout && action_has_layout? && !layout_name
raise ArgumentError,
"There was no default layout for #{self.class} in #{view_paths.inspect}"
end
layout_name
end
def _include_layout?(options)
(options.keys & [:text, :inline, :partial]).empty? || options.key?(:layout)
end
end
end
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