@@ -154,7 +154,7 @@ Every Rails application comes with a standard set of middleware which it uses in
* +Rails::Rack::Logger+ Will notify the logs that the request has began. After request is complete, flushes all the logs.
* +ActionDispatch::ShowExceptions+ rescues any exception returned by the application and renders nice exception pages if the request is local or if +config.consider_all_requests_local+ is set to _true_. If +config.action_dispatch.show_exceptions+ is set to _false_, exceptions will be raised regardless.
* +ActionDispatch::RemoteIp+ checks for IP spoofing attacks. Configurable with the +config.action_dispatch.ip_spoofing_check+ and +config.action_dispatch.trusted_proxies+ settings.
* +Rack::Sendfile+ The Sendfile middleware intercepts responses whose body is being served from a file and replaces it with a server specific X-Sendfile header. Configurable with +config.action_dispatch_
* +Rack::Sendfile+ The Sendfile middleware intercepts responses whose body is being served from a file and replaces it with a server specific X-Sendfile header. Configurable with +config.action_dispatch.x_sendfile_header+
* +ActionDispatch::Callbacks+ Runs the prepare callbacks before serving the request.
* +ActiveRecord::ConnectionAdapters::ConnectionManagement+ cleans active connections after each request, unless the +rack.test+ key in the request environment is set to _true_.
* +ActiveRecord::QueryCache+ caches all +SELECT+ queries generated in a request. If an +INSERT+ or +UPDATE+ takes place then the cache is cleaned.
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@@ -376,8 +376,15 @@ There are a few configuration options available in Active Support:
* +ActiveSupport::Cache::Store.logger+ specifies the logger to use within cache store operations.
* +ActiveSupport::Deprecation.behavior+ alternative setter to +config.active_support.deprecation+ which configures the behavior of deprecation warnings for Rails.
* +ActiveSupport::Deprecation.silence+ takes a block in which all deprecation warnings are silenced.
* +ActiveSupport::Deprecation.silenced+ sets whether or not to display deprecation warnings.
* +ActiveSupport::Logger.silencer+ is set to +false+ to disable the ability to silence logging in a block. The default is +true+.
h3. Rails Environment Settings
Some parts of Rails can also be configured externally by supplying environment variables. The following environment variables are recognized by various parts of Rails:
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@@ -464,7 +471,7 @@ You might have expected an instance of Array.
The error occurred while evaluating nil.each
</plain>
*+active_support.deprecation_behavior+* Sets up deprecation reporting for environments, defaulting to +log+ for development, +notify+ for production and +stderr+ for test. If a value isn't set for +config.active_support.deprecation+ then this initializer will prompt the user to configure this line in the current environment's +config/environments+ file.
*+active_support.deprecation_behavior+* Sets up deprecation reporting for environments, defaulting to +:log+ for development, +:notify+ for production and +:stderr+ for test. If a value isn't set for +config.active_support.deprecation+ then this initializer will prompt the user to configure this line in the current environment's +config/environments+ file. Can be set to an array of values.
*+active_support.initialize_time_zone+* Sets the default time zone for the application based off the +config.time_zone+ setting, which defaults to "UTC".
The +ActiveSupport::FileUpdateChecker+ class defined within this file is responsible for checking if a file has been updated since it was last checked. This is used for monitoring the routes file for changes during development environment runs.
h4. +railties/lib/rails/plugin.rb+
This file defines +Rails::Plugin+ which inherits from +Rails::Engine+. Unlike +Rails::Engine+ and +Rails::Railtie+ however, this class is not designed to be inherited from. Instead, this is used simply for loading plugins from within an application and an engine.
This file begins by requiring +rails/engine.rb+
h4. +railties/lib/rails/engine.rb+
The +rails/engine.rb+ file defines the +Rails::Engine+ class which inherits from +Rails::Railtie+. The +Rails::Engine+ class defines much of the functionality found within a standard application class such as the +routes+ and +config+ methods.
The "API documentation":http://api.rubyonrails.org/classes/Rails/Engine.html for +Rails::Engine+ explains the function of this class pretty well.
This file's first line requires +rails/railtie.rb+.
h4. +railties/lib/rails/railtie.rb+
The +rails/railtie.rb+ file is responsible for defining +Rails::Railtie+, the underlying class for all ties to Rails now. Gems that want to have their own initializers or rake tasks and hook into Rails should have a +GemName::Railtie+ class that inherits from +Rails::Railtie+.
The "API documentation":http://api.rubyonrails.org/classes/Rails/Railtie.html for +Rails::Railtie+, much like +Rails::Engine+, explains this class exceptionally well.
The first require in this file is +rails/initializable.rb+.
h4. +railties/lib/rails/initializable.rb+
Now we reach the end of this particular rabbit hole as +rails/initializable.rb+ doesn't require any more Rails files, only +tsort+ from the Ruby standard library.
This file defines the +Rails::Initializable+ module which contains the +Initializer+ class, the basis for all initializers in Rails. This module also contains a +ClassMethods+ class which will be included into the +Rails::Railtie+ class when these requires have finished.
Now that +rails/initializable.rb+ has finished being required from +rails/railtie.rb+, the next require is for +rails/configuration+.
h4. +railties/lib/rails/configuration.rb+
This file defines the +Rails::Configuration+ module, containing the +MiddlewareStackProxy+ class as well as the +Generators+ class. The +MiddlewareStackProxy+ class is used for managing the middleware stack for an application, which we'll see later on. The +Generators+ class provides the functionality used for configuring what generators an application uses through the "+config.generators+ option":http://guides.rubyonrails.org/configuring.html#configuring-generators.
The first file required in this file is +activesupport/deprecation+.
This file, and the files it requires, define the basic deprecation warning features found in Rails. This file is responsible for setting defaults in the +ActiveSupport::Deprecation+ module for the +deprecation_horizon+, +silenced+ and +debug+ values. The files that are required before this happens are:
This file defines the behavior of the +ActiveSupport::Deprecation+ module, setting up the +DEFAULT_BEHAVIORS+ hash constant which contains the three defaults to outputting deprecation warnings: +:stderr+, +:log+ and +:notify+. This file begins by requiring +activesupport/notifications+ and +activesupport/core_ext/array/wrap+.
As this file comprises of a core extension, it is covered exclusively in "the Active Support Core Extensions guide":http://guides.rubyonrails.org/active_support_core_extensions.html#wrapping
This file is responsible for defining the +warn+ and +silence+ methods for +ActiveSupport::Deprecation+ as well as additional private methods for this module.
This file defines a +deprecate_methods+ which is primarily used by the +module/deprecation+ core extension required by the first line of this file. Other core extensions required by this file are the +module/aliasing+ and +array/extract_options+ files.
+proxy_wrappers.rb+ defines deprecation wrappers for methods, instance variables and constants. Previously, this was used for the +RAILS_ENV+ and +RAILS_ROOT+ constants for 3.0 but since then these constants have been removed. The deprecation message that would be raised from these would be something like:
<plain>
BadConstant is deprecated! Use GoodConstant instead.
</plain>
h4. +active_support/ordered_options+
This file is the next file required from +rails/configuration.rb+ is the file that defines +ActiveSupport::OrderedOptions+ which is used for configuration options such as +config.active_support+ and the like.
The next file required is +active_support/core_ext/hash/deep_dup+ which is covered in "Active Support Core Extensions guide":http://guides.rubyonrails.org/active_support_core_extensions.html#deep_dup
Creating a form for a model _and_ its associations can become quite tedious. Therefor Rails provides helpers to assist in dealing with the complexities of generating these forms _and_ the required CRUD operations to create, update, and destroy associations.
Creating a form for a model _and_ its associations can become quite tedious. Therefore Rails provides helpers to assist in dealing with the complexities of generating these forms _and_ the required CRUD operations to create, update, and destroy associations.
* "Ruby on Rack #1 - Hello Rack!":http://m.onkey.org/2008/11/17/ruby-on-rack-1
* "Ruby on Rack #2 - The Builder":http://m.onkey.org/2008/11/18/ruby-on-rack-2-rack-builder
Explaining Rack is not really in the scope of this guide. In case you are not familiar with Rack's basics, you should check out the "Resources":#resources section below.
h3. Rails on Rack
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@@ -165,7 +160,7 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
|_.Middleware|_.Purpose|
|+Rack::Lock+|Sets +env["rack.multithread"]+ flag to +true+ and wraps the application within a Mutex.|
|+ActionController::Failsafe+|Returns HTTP Status +500+ to the client if an exception gets raised while dispatching.|
|+ActiveRecord::QueryCache+|Enable the Active Record query cache.|
|+ActiveRecord::QueryCache+|Enables the Active Record query cache.|
|+ActionController::Session::CookieStore+|Uses the cookie based session store.|
|+ActionController::Session::MemCacheStore+|Uses the memcached based session store.|
|+ActiveRecord::SessionStore+|Uses the database based session store.|