311 lines
13 KiB
Ruby
311 lines
13 KiB
Ruby
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module ActionController #:nodoc:
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module Layout #:nodoc:
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def self.included(base)
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base.extend(ClassMethods)
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base.class_eval do
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alias_method :render_with_no_layout, :render
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alias_method :render, :render_with_a_layout
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class << self
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alias_method :inherited_without_layout, :inherited
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alias_method :inherited, :inherited_with_layout
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end
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end
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end
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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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# Not a word about common structures. At rendering time, the content page is computed and then inserted in the layout,
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# 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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# == Automatic layout assignment
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#
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# If there is a template in <tt>app/views/layouts/</tt> with the same name as the current controller then it will be automatically
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# set as that controller's layout unless explicitly told otherwise. Say you have a WeblogController, for example. If a template named
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# <tt>app/views/layouts/weblog.rhtml</tt> or <tt>app/views/layouts/weblog.rxml</tt> exists then it will be automatically set as
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# the layout for your WeblogController. You can create a layout with the name <tt>application.rhtml</tt> or <tt>application.rxml</tt>
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# 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
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# no layout explicitly assigned with the +layout+ method. Nested controllers use the same folder structure for automatic layout.
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# assignment. So an Admin::WeblogController will look for a template named <tt>app/views/layouts/admin/weblog.rhtml</tt>.
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# Setting a layout explicitly will always override the automatic behaviour for the controller where the layout is set.
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# Explicitly setting the layout in a parent class, though, will not override the child class's layout assignement if the child
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# class has a layout with the same name.
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#
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# == Inheritance for layouts
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#
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# Layouts are shared downwards in the inheritance hierarchy, but not upwards. 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 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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# == 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 by looked for in +app/views/layouts/+.
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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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# Some times you'll have exceptions, though, where one action wants to use a different layout than the rest of the controller.
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# This is possible using the <tt>render</tt> method. It's just a bit more manual work as you'll have to supply fully
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# qualified template and layout names as this example shows:
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#
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# class WeblogController < ActionController::Base
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# def help
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# render :action => "help/index", :layout => "help"
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# end
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# end
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#
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# As you can see, you pass the template as the first parameter, the status code as the second ("200" is OK), and the layout
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# as the third.
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#
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# NOTE: The old notation for rendering the view from a layout was to expose the magic <tt>@content_for_layout</tt> instance
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# variable. The preferred notation now is to use <tt>yield</tt>, as documented above.
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module ClassMethods
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# If a layout is specified, all rendered actions will have their result rendered
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# when the layout<tt>yield</tt>'s. This layout can itself depend on instance variables assigned during action
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# performance and have access to them as any normal template would.
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def layout(template_name, conditions = {})
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add_layout_conditions(conditions)
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write_inheritable_attribute "layout", template_name
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end
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def layout_conditions #:nodoc:
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@layout_conditions ||= read_inheritable_attribute("layout_conditions")
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end
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def default_layout #:nodoc:
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@default_layout ||= read_inheritable_attribute("layout")
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end
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private
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def inherited_with_layout(child)
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inherited_without_layout(child)
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child.send :include, Reloadable
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layout_match = child.name.underscore.sub(/_controller$/, '').sub(/^controllers\//, '')
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child.layout(layout_match) unless layout_list.grep(%r{layouts/#{layout_match}\.[a-z][0-9a-z]*$}).empty?
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end
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def layout_list
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Dir.glob("#{template_root}/layouts/**/*")
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end
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def add_layout_conditions(conditions)
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write_inheritable_hash "layout_conditions", normalize_conditions(conditions)
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end
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def normalize_conditions(conditions)
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conditions.inject({}) {|hash, (key, value)| hash.merge(key => [value].flatten.map {|action| action.to_s})}
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end
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def layout_directory_exists_cache
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@@layout_directory_exists_cache ||= Hash.new do |h, dirname|
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h[dirname] = File.directory? dirname
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end
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end
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end
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# Returns the name of the active layout. If the layout was specified as a method reference (through a symbol), this method
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# is called and the return value is used. Likewise if the layout was specified as an inline method (through a proc or method
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# object). If the layout was defined without a directory, layouts is assumed. So <tt>layout "weblog/standard"</tt> will return
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# weblog/standard, but <tt>layout "standard"</tt> will return layouts/standard.
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def active_layout(passed_layout = nil)
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layout = passed_layout || self.class.default_layout
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active_layout = case layout
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when String then layout
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when Symbol then send(layout)
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when Proc then layout.call(self)
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end
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# Explicitly passed layout names with slashes are looked up relative to the template root,
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# but auto-discovered layouts derived from a nested controller will contain a slash, though be relative
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# to the 'layouts' directory so we have to check the file system to infer which case the layout name came from.
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if active_layout
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if active_layout.include?('/') && ! layout_directory?(active_layout)
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active_layout
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else
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"layouts/#{active_layout}"
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end
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end
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end
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def render_with_a_layout(options = nil, deprecated_status = nil, deprecated_layout = nil, &block) #:nodoc:
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template_with_options = options.is_a?(Hash)
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if apply_layout?(template_with_options, options) && (layout = pick_layout(template_with_options, options, deprecated_layout))
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options = options.merge :layout => false if template_with_options
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logger.info("Rendering #{options} within #{layout}") if logger
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if template_with_options
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content_for_layout = render_with_no_layout(options, &block)
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deprecated_status = options[:status] || deprecated_status
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else
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content_for_layout = render_with_no_layout(options, deprecated_status, &block)
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end
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erase_render_results
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add_variables_to_assigns
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@template.instance_variable_set("@content_for_layout", content_for_layout)
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render_text(@template.render_file(layout, true), deprecated_status)
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else
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render_with_no_layout(options, deprecated_status, &block)
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end
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end
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private
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def apply_layout?(template_with_options, options)
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return false if options == :update
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template_with_options ? candidate_for_layout?(options) : !template_exempt_from_layout?
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end
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def candidate_for_layout?(options)
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(options.has_key?(:layout) && options[:layout] != false) ||
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options.values_at(:text, :xml, :file, :inline, :partial, :nothing).compact.empty? &&
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!template_exempt_from_layout?(default_template_name(options[:action] || options[:template]))
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end
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def pick_layout(template_with_options, options, deprecated_layout)
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if deprecated_layout
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deprecated_layout
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elsif template_with_options
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case layout = options[:layout]
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when FalseClass
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nil
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when NilClass, TrueClass
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active_layout if action_has_layout?
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else
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active_layout(layout)
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end
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else
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active_layout if action_has_layout?
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end
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end
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def action_has_layout?
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if conditions = self.class.layout_conditions
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case
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when only = conditions[:only]
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only.include?(action_name)
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when except = conditions[:except]
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!except.include?(action_name)
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else
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true
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end
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else
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true
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end
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end
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# Does a layout directory for this class exist?
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# we cache this info in a class level hash
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def layout_directory?(layout_name)
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template_path = File.join(self.class.view_root, 'layouts', layout_name)
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dirname = File.dirname(template_path)
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self.class.send(:layout_directory_exists_cache)[dirname]
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end
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end
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end
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