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192 lines
7.5 KiB
Ruby
192 lines
7.5 KiB
Ruby
module ActionController
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# Layouts reverse the common pattern of including shared headers and footers in many templates to isolate changes in
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# repeated setups. The inclusion pattern has pages that look like this:
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#
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# <%= render "shared/header" %>
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# Hello World
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# <%= render "shared/footer" %>
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#
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# This approach is a decent way of keeping common structures isolated from the changing content, but it's verbose
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# and if you ever want to change the structure of these two includes, you'll have to change all the templates.
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#
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# With layouts, you can flip it around and have the common structure know where to insert changing content. This means
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# that the header and footer are only mentioned in one place, like this:
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#
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# // The header part of this layout
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# <%= yield %>
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# // The footer part of this layout
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#
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# And then you have content pages that look like this:
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#
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# hello world
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#
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# At rendering time, the content page is computed and then inserted in the layout, like this:
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#
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# // The header part of this layout
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# hello world
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# // The footer part of this layout
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#
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# == Accessing shared variables
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#
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# Layouts have access to variables specified in the content pages and vice versa. This allows you to have layouts with
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# references that won't materialize before rendering time:
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#
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# <h1><%= @page_title %></h1>
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# <%= yield %>
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#
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# ...and content pages that fulfill these references _at_ rendering time:
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#
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# <% @page_title = "Welcome" %>
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# Off-world colonies offers you a chance to start a new life
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#
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# The result after rendering is:
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#
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# <h1>Welcome</h1>
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# Off-world colonies offers you a chance to start a new life
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#
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# == Layout assignment
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#
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# You can either specify a layout declaratively (using the #layout class method) or give
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# it the same name as your controller, and place it in <tt>app/views/layouts</tt>.
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# If a subclass does not have a layout specified, it inherits its layout using normal Ruby inheritance.
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#
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# For instance, if you have PostsController and a template named <tt>app/views/layouts/posts.html.erb</tt>,
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# that template will be used for all actions in PostsController and controllers inheriting
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# from PostsController.
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#
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# If you use a module, for instance Weblog::PostsController, you will need a template named
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# <tt>app/views/layouts/weblog/posts.html.erb</tt>.
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#
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# Since all your controllers inherit from ApplicationController, they will use
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# <tt>app/views/layouts/application.html.erb</tt> if no other layout is specified
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# or provided.
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#
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# == Inheritance Examples
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#
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# class BankController < ActionController::Base
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# layout "bank_standard"
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#
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# class InformationController < BankController
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#
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# class TellerController < BankController
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# # teller.html.erb exists
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#
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# class TillController < TellerController
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#
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# class VaultController < BankController
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# layout :access_level_layout
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#
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# class EmployeeController < BankController
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# layout nil
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#
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# The InformationController uses "bank_standard" inherited from the BankController, the VaultController overwrites
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# and picks the layout dynamically, and the EmployeeController doesn't want to use a layout at all.
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#
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# The TellerController uses +teller.html.erb+, and TillController inherits that layout and
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# uses it as well.
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#
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# == Types of layouts
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#
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# Layouts are basically just regular templates, but the name of this template needs not be specified statically. Sometimes
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# you want to alternate layouts depending on runtime information, such as whether someone is logged in or not. This can
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# be done either by specifying a method reference as a symbol or using an inline method (as a proc).
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#
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# The method reference is the preferred approach to variable layouts and is used like this:
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#
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# class WeblogController < ActionController::Base
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# layout :writers_and_readers
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#
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# def index
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# # fetching posts
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# end
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#
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# private
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# def writers_and_readers
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# logged_in? ? "writer_layout" : "reader_layout"
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# end
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#
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# Now when a new request for the index action is processed, the layout will vary depending on whether the person accessing
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# is logged in or not.
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#
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# If you want to use an inline method, such as a proc, do something like this:
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#
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# class WeblogController < ActionController::Base
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# layout proc{ |controller| controller.logged_in? ? "writer_layout" : "reader_layout" }
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#
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# Of course, the most common way of specifying a layout is still just as a plain template name:
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#
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# class WeblogController < ActionController::Base
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# layout "weblog_standard"
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#
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# If no directory is specified for the template name, the template will by default be looked for in <tt>app/views/layouts/</tt>.
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# Otherwise, it will be looked up relative to the template root.
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#
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# == Conditional layouts
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#
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# If you have a layout that by default is applied to all the actions of a controller, you still have the option of rendering
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# 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
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# <tt>:only</tt> and <tt>:except</tt> options can be passed to the layout call. For example:
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#
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# class WeblogController < ActionController::Base
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# layout "weblog_standard", :except => :rss
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#
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# # ...
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#
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# end
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#
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# This will assign "weblog_standard" as the WeblogController's layout except for the +rss+ action, which will not wrap a layout
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# around the rendered view.
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#
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# Both the <tt>:only</tt> and <tt>:except</tt> condition can accept an arbitrary number of method references, so
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# #<tt>:except => [ :rss, :text_only ]</tt> is valid, as is <tt>:except => :rss</tt>.
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#
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# == Using a different layout in the action render call
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#
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# If most of your actions use the same layout, it makes perfect sense to define a controller-wide layout as described above.
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# Sometimes you'll have exceptions where one action wants to use a different layout than the rest of the controller.
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# You can do this by passing a <tt>:layout</tt> option to the <tt>render</tt> call. For example:
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#
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# class WeblogController < ActionController::Base
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# layout "weblog_standard"
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#
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# def help
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# render :action => "help", :layout => "help"
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# end
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# end
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#
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# This will render the help action with the "help" layout instead of the controller-wide "weblog_standard" layout.
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module Layouts
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extend ActiveSupport::Concern
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include ActionController::Renderer
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include AbstractController::Layouts
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module ClassMethods
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# If no layout is provided, look for a layout with this name.
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def _implied_layout_name
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controller_path
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end
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end
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private
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def _determine_template(options)
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super
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return if (options.key?(:text) || options.key?(:inline) || options.key?(:partial)) && !options.key?(:layout)
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layout = options.key?(:layout) ? options[:layout] : :default
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options[:_layout] = _layout_for_option(layout, options[:_template].details)
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end
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def _layout_for_option(name, details)
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case name
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when String then _layout_for_name(name, details)
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when true then _default_layout(details, true)
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when :default then _default_layout(details, false)
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when false, nil then nil
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else
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raise ArgumentError,
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"String, true, or false, expected for `layout'; you passed #{name.inspect}"
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end
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end
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end
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end
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