435 lines
16 KiB
Ruby
435 lines
16 KiB
Ruby
# frozen_string_literal: true
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require "action_view/rendering"
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require "active_support/core_ext/module/redefine_method"
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module ActionView
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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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# # bank.html.erb exists
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#
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# class ExchangeController < BankController
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# # exchange.html.erb exists
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#
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# class CurrencyController < BankController
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#
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# class InformationController < BankController
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# layout "information"
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#
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# class TellerController < InformationController
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# # teller.html.erb exists
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#
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# class EmployeeController < InformationController
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# # employee.html.erb exists
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# layout nil
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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 TillController < BankController
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# layout false
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#
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# In these examples, we have three implicit lookup scenarios:
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# * The +BankController+ uses the "bank" layout.
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# * The +ExchangeController+ uses the "exchange" layout.
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# * The +CurrencyController+ inherits the layout from BankController.
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#
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# However, when a layout is explicitly set, the explicitly set layout wins:
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# * The +InformationController+ uses the "information" layout, explicitly set.
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# * The +TellerController+ also uses the "information" layout, because the parent explicitly set it.
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# * The +EmployeeController+ uses the "employee" layout, because it set the layout to +nil+, resetting the parent configuration.
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# * The +VaultController+ chooses a layout dynamically by calling the <tt>access_level_layout</tt> method.
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# * The +TillController+ does not 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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# 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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# end
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#
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# If an argument isn't given to the proc, it's evaluated in the context of
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# the current controller anyway.
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#
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# class WeblogController < ActionController::Base
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# layout proc { logged_in? ? "writer_layout" : "reader_layout" }
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# end
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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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# end
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#
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# The template will be looked always in <tt>app/views/layouts/</tt> folder. But you can point
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# <tt>layouts</tt> folder direct also. <tt>layout "layouts/demo"</tt> is the same as <tt>layout "demo"</tt>.
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#
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# Setting the layout to +nil+ forces it to be looked up in the filesystem and fallbacks to the parent behavior if none exists.
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# Setting it to +nil+ is useful to re-enable template lookup overriding a previous configuration set in the parent:
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#
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# class ApplicationController < ActionController::Base
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# layout "application"
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# end
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#
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# class PostsController < ApplicationController
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# # Will use "application" layout
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# end
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#
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# class CommentsController < ApplicationController
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# # Will search for "comments" layout and fallback "application" layout
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# layout nil
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# end
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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 for all actions except for the +rss+ action, which will
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# be rendered directly, without wrapping a layout 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 override the controller-wide "weblog_standard" layout, and will render the help action with the "help" layout instead.
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module Layouts
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extend ActiveSupport::Concern
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include ActionView::Rendering
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included do
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class_attribute :_layout, instance_accessor: false
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class_attribute :_layout_conditions, instance_accessor: false, default: {}
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_write_layout_method
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end
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delegate :_layout_conditions, to: :class
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module ClassMethods
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def inherited(klass) # :nodoc:
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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 # :nodoc:
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private
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# Determines whether the current action has a layout definition by
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# checking the action name against the :only and :except conditions
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# set by the <tt>layout</tt> method.
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#
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# ==== Returns
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# * <tt>Boolean</tt> - True if the action has a layout definition, false otherwise.
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def _conditional_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
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# Proc:: call the passed Proc
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# false:: There is no layout
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# true:: raise an ArgumentError
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# nil:: Force default layout behavior with inheritance
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#
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# Return value of +Proc+ and +Symbol+ arguments should be +String+, +false+, +true+, or +nil+
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# with the same meaning as described above.
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#
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# ==== Parameters
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#
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# * <tt>layout</tt> - The layout to use.
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#
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# ==== Options (conditions)
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#
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# * +:only+ - A list of actions to apply this layout to.
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# * +:except+ - 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(&:to_s) }
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self._layout_conditions = conditions
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self._layout = layout
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_write_layout_method
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end
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# Creates a _layout method to be called by _default_layout .
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#
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# If a layout is not explicitly mentioned then look for a layout with the controller's name.
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# if nothing is found then try same procedure to find super class's layout.
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def _write_layout_method # :nodoc:
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silence_redefinition_of_method(:_layout)
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prefixes = /\blayouts/.match?(_implied_layout_name) ? [] : ["layouts"]
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default_behavior = "lookup_context.find_all('#{_implied_layout_name}', #{prefixes.inspect}, false, [], { formats: formats }).first || super"
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name_clause = if name
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default_behavior
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else
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<<-RUBY
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super
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RUBY
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end
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layout_definition = \
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case _layout
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when String
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_layout.inspect
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when Symbol
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<<-RUBY
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#{_layout}.tap do |layout|
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return #{default_behavior} if layout.nil?
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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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RUBY
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when Proc
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define_method :_layout_from_proc, &_layout
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private :_layout_from_proc
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<<-RUBY
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result = _layout_from_proc(#{_layout.arity == 0 ? '' : 'self'})
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return #{default_behavior} if result.nil?
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result
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RUBY
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when false
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nil
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when true
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raise ArgumentError, "Layouts must be specified as a String, Symbol, Proc, false, or nil"
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when nil
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name_clause
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end
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class_eval <<-RUBY, __FILE__, __LINE__ + 1
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# frozen_string_literal: true
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def _layout(lookup_context, formats)
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if _conditional_layout?
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#{layout_definition}
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else
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#{name_clause}
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end
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end
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private :_layout
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RUBY
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end
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private
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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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# * <tt>String</tt> - 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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end
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def _normalize_options(options) # :nodoc:
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super
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if _include_layout?(options)
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layout = options.delete(:layout) { :default }
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options[:layout] = _layout_for_option(layout)
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end
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end
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attr_internal_writer :action_has_layout
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def initialize(*) # :nodoc:
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@_action_has_layout = true
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super
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end
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# Controls whether an action should be rendered using a layout.
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# If you want to disable any <tt>layout</tt> settings for the
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# current action so that it is rendered without a layout then
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# either override this method in your controller to return false
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# for that action or set the <tt>action_has_layout</tt> attribute
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# to false before rendering.
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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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def _conditional_layout?
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true
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end
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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, taking into account the name type.
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#
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# ==== Parameters
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# * <tt>name</tt> - The name of the template
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def _layout_for_option(name)
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case name
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when String then _normalize_layout(name)
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when Proc then name
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when true then Proc.new { |lookup_context, formats| _default_layout(lookup_context, formats, true) }
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when :default then Proc.new { |lookup_context, formats| _default_layout(lookup_context, formats, 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, Proc, :default, true, or false, expected for `layout'; you passed #{name.inspect}"
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end
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end
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def _normalize_layout(value)
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value.is_a?(String) && !value.match?(/\blayouts/) ? "layouts/#{value}" : value
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end
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# Returns the default layout for this controller.
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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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# * <tt>formats</tt> - The formats accepted to this layout
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# * <tt>require_layout</tt> - If set to +true+ and layout is not found,
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# an +ArgumentError+ exception is raised (defaults to +false+)
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#
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# ==== Returns
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# * <tt>template</tt> - The template object for the default layout (or +nil+)
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def _default_layout(lookup_context, formats, require_layout = false)
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begin
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value = _layout(lookup_context, formats) if action_has_layout?
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rescue NameError => e
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raise e, "Could not render layout: #{e.message}"
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end
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if require_layout && action_has_layout? && !value
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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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_normalize_layout(value)
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end
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def _include_layout?(options)
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(options.keys & [:body, :plain, :html, :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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