aboutsummaryrefslogtreecommitdiffstats
path: root/actionpack/lib/action_controller/base/layout.rb
diff options
context:
space:
mode:
Diffstat (limited to 'actionpack/lib/action_controller/base/layout.rb')
-rw-r--r--actionpack/lib/action_controller/base/layout.rb247
1 files changed, 247 insertions, 0 deletions
diff --git a/actionpack/lib/action_controller/base/layout.rb b/actionpack/lib/action_controller/base/layout.rb
new file mode 100644
index 0000000000..4fcef6c5d9
--- /dev/null
+++ b/actionpack/lib/action_controller/base/layout.rb
@@ -0,0 +1,247 @@
+module ActionController #:nodoc:
+ module Layout #:nodoc:
+ def self.included(base)
+ base.extend(ClassMethods)
+ base.class_inheritable_accessor :layout_name, :layout_conditions
+ 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
+ #
+ # 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
+ #
+ # 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.
+ #
+ # == 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 assignment 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 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 ClassMethods
+ extend ActiveSupport::Memoizable
+
+ # 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 = {}, auto = false)
+ add_layout_conditions(conditions)
+ self.layout_name = template_name
+ end
+
+ def memoized_default_layout(formats) #:nodoc:
+ self.layout_name || begin
+ layout = default_layout_name
+ layout.is_a?(String) ? find_layout(layout, formats) : layout
+ rescue ActionView::MissingTemplate
+ end
+ end
+
+ def default_layout(*args)
+ memoized_default_layout(*args)
+ @_memoized_default_layout ||= ::ActiveSupport::ConcurrentHash.new
+ @_memoized_default_layout[args] ||= memoized_default_layout(*args)
+ end
+
+ def memoized_find_layout(layout, formats) #:nodoc:
+ return layout if layout.nil? || layout.respond_to?(:render)
+ prefix = layout.to_s =~ /layouts\// ? nil : "layouts"
+ view_paths.find_by_parts(layout.to_s, formats, prefix)
+ end
+
+ def find_layout(*args)
+ @_memoized_find_layout ||= ::ActiveSupport::ConcurrentHash.new
+ @_memoized_find_layout[args] ||= memoized_find_layout(*args)
+ end
+
+ def layout_list #:nodoc:
+ Array(view_paths).sum([]) { |path| Dir["#{path.to_str}/layouts/**/*"] }
+ end
+ memoize :layout_list
+
+ def default_layout_name
+ layout_match = name.underscore.sub(/_controller$/, '')
+ if layout_list.grep(%r{layouts/#{layout_match}(\.[a-z][0-9a-z]*)+$}).empty?
+ superclass.default_layout_name if superclass.respond_to?(:default_layout_name)
+ else
+ layout_match
+ end
+ end
+ memoize :default_layout_name
+
+ private
+ def add_layout_conditions(conditions)
+ # :except => :foo == :except => [:foo] == :except => "foo" == :except => ["foo"]
+ conditions.each {|k, v| conditions[k] = Array(v).map {|a| a.to_s} }
+ write_inheritable_hash(:layout_conditions, conditions)
+ end
+ end
+
+ def active_layout(name)
+ name = self.class.default_layout(formats) if name == true
+
+ layout_name = case name
+ when Symbol then __send__(name)
+ when Proc then name.call(self)
+ else name
+ end
+
+ self.class.find_layout(layout_name, formats)
+ end
+
+ def _pick_layout(layout_name = nil, implicit = false)
+ return unless layout_name || implicit
+ layout_name = true if layout_name.nil?
+ active_layout(layout_name) if action_has_layout? && layout_name
+ end
+
+ private
+ def action_has_layout?
+ if conditions = self.class.layout_conditions
+ if only = conditions[:only]
+ return only.include?(action_name)
+ elsif except = conditions[:except]
+ return !except.include?(action_name)
+ end
+ end
+ true
+ end
+
+ end
+end