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Diffstat (limited to 'actionpack/lib/action_controller/base/layout.rb')
| -rw-r--r-- | actionpack/lib/action_controller/base/layout.rb | 247 |
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 |