365 lines
13 KiB
Ruby
365 lines
13 KiB
Ruby
require "active_support/core_ext/module/remove_method"
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module AbstractController
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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 Rendering
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included do
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class_attribute :_layout_conditions
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delegate :_layout_conditions, :to => :'self.class'
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self._layout_conditions = {}
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_write_layout_method
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end
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module ClassMethods
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def inherited(klass)
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super
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klass._write_layout_method
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end
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# This module is mixed in if layout conditions are provided. This means
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# that if no layout conditions are used, this method is not used
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module LayoutConditions
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# Determines whether the current action has a layout by checking the
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# action name against the :only and :except conditions set on the
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# layout.
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#
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# ==== Returns
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# Boolean:: True if the action has a layout, false otherwise.
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def action_has_layout?
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return unless super
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conditions = _layout_conditions
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if only = conditions[:only]
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only.include?(action_name)
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elsif 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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end
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end
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# Specify the layout to use for this class.
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#
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# If the specified layout is a:
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# String:: the String is the template name
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# Symbol:: call the method specified by the symbol, which will return
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# the template name
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# false:: There is no layout
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# true:: raise an ArgumentError
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#
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# ==== Parameters
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# layout<String, Symbol, false)>:: The layout to use.
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#
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# ==== Options (conditions)
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# :only<#to_s, Array[#to_s]>:: A list of actions to apply this layout to.
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# :except<#to_s, Array[#to_s]>:: Apply this layout to all actions but this one
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def layout(layout, conditions = {})
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include LayoutConditions unless conditions.empty?
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conditions.each {|k, v| conditions[k] = Array(v).map {|a| a.to_s} }
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self._layout_conditions = conditions
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@_layout = layout || false # Converts nil to false
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_write_layout_method
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end
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# If no layout is supplied, look for a template named the return
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# value of this method.
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#
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# ==== Returns
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# String:: A template name
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def _implied_layout_name
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controller_path
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end
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# Takes the specified layout and creates a _layout method to be called
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# by _default_layout
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#
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# If there is no explicit layout specified:
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# If a layout is found in the view paths with the controller's
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# name, return that string. Otherwise, use the superclass'
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# layout (which might also be implied)
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def _write_layout_method
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remove_possible_method(:_layout)
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case defined?(@_layout) ? @_layout : nil
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when String
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self.class_eval %{def _layout; #{@_layout.inspect} end}, __FILE__, __LINE__
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when Symbol
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self.class_eval <<-ruby_eval, __FILE__, __LINE__ + 1
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def _layout
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#{@_layout}.tap do |layout|
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unless layout.is_a?(String) || !layout
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raise ArgumentError, "Your layout method :#{@_layout} returned \#{layout}. It " \
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"should have returned a String, false, or nil"
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end
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end
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end
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ruby_eval
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when Proc
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define_method :_layout_from_proc, &@_layout
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self.class_eval %{def _layout; _layout_from_proc(self) end}, __FILE__, __LINE__
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when false
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self.class_eval %{def _layout; end}, __FILE__, __LINE__
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when true
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raise ArgumentError, "Layouts must be specified as a String, Symbol, false, or nil"
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when nil
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if name
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_prefix = "layouts" unless _implied_layout_name =~ /\blayouts/
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self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
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def _layout
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if template_exists?("#{_implied_layout_name}", #{_prefix.inspect})
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"#{_implied_layout_name}"
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else
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super
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end
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end
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RUBY
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end
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end
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self.class_eval { private :_layout }
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end
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end
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def _normalize_options(options)
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super
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if _include_layout?(options)
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layout = options.key?(:layout) ? options.delete(:layout) : :default
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value = _layout_for_option(layout)
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options[:layout] = (value =~ /\blayouts/ ? value : "layouts/#{value}") if value
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end
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end
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attr_writer :action_has_layout
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def initialize(*)
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@action_has_layout = true
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super
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end
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def action_has_layout?
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@action_has_layout
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end
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private
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# This will be overwritten by _write_layout_method
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def _layout; end
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# Determine the layout for a given name and details, taking into account
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# the name type.
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#
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# ==== Parameters
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# name<String|TrueClass|FalseClass|Symbol>:: The name of the template
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# details<Hash{Symbol => Object}>:: A list of details to restrict
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# the lookup to. By default, layout lookup is limited to the
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# formats specified for the current request.
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def _layout_for_option(name)
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case name
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when String then name
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when true then _default_layout(true)
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when :default then _default_layout(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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# Returns the default layout for this controller and a given set of details.
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# Optionally raises an exception if the layout could not be found.
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#
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# ==== Parameters
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# details<Hash>:: A list of details to restrict the search by. This
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# might include details like the format or locale of the template.
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# require_layout<Boolean>:: If this is true, raise an ArgumentError
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# with details about the fact that the exception could not be
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# found (defaults to false)
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#
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# ==== Returns
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# Template:: The template object for the default layout (or nil)
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def _default_layout(require_layout = false)
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begin
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layout_name = _layout if action_has_layout?
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rescue NameError => e
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raise NoMethodError,
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"You specified #{@_layout.inspect} as the layout, but no such method was found"
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end
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if require_layout && action_has_layout? && !layout_name
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raise ArgumentError,
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"There was no default layout for #{self.class} in #{view_paths.inspect}"
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end
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layout_name
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end
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def _include_layout?(options)
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(options.keys & [:text, :inline, :partial]).empty? || options.key?(:layout)
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end
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end
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end
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