Class: ActionController::Base

Inherits:
Object
  • Object
show all
Includes:
ClassInheritableAttributes
Defined in:
lib/action_controller/base.rb,
lib/action_controller/cgi_process.rb,
lib/action_controller/test_process.rb

Overview

Action Controllers are made up of one or more actions that performs its purpose and then either renders a template or redirects to another action. An action is defined as a public method on the controller, which will automatically be made accessible to the web-server through a mod_rewrite mapping. A sample controller could look like this:

class GuestBookController < ActionController::Base
  def index
    @entries = Entry.find_all
  end

  def sign
    Entry.create(@params["entry"])
    redirect_to :action => "index"
  end
end

GuestBookController.template_root = "templates/"
GuestBookController.process_cgi

All actions assume that you want to render a template matching the name of the action at the end of the performance unless you tell it otherwise. The index action complies with this assumption, so after populating the @entries instance variable, the GuestBookController will render “templates/guestbook/index.rhtml”.

Unlike index, the sign action isn’t interested in rendering a template. So after performing its main purpose (creating a new entry in the guest book), it sheds the rendering assumption and initiates a redirect instead. This redirect works by returning an external “302 Moved” HTTP response that takes the user to the index action.

The index and sign represent the two basic action archetypes used in Action Controllers. Get-and-show and do-and-redirect. Most actions are variations of these themes.

Also note that it’s the final call to process_cgi that actually initiates the action performance. It will extract request and response objects from the CGI

Requests

Requests are processed by the Action Controller framework by extracting the value of the “action” key in the request parameters. This value should hold the name of the action to be performed. Once the action has been identified, the remaining request parameters, the session (if one is available), and the full request with all the http headers are made available to the action through instance variables. Then the action is performed.

The full request object is available in @request and is primarily used to query for http headers. These queries are made by accessing the environment hash, like this:

def hello_ip
  location = @request.env["REMOTE_IP"]
  render_text "Hello stranger from #{location}"
end

Parameters

All request parameters whether they come from a GET or POST request, or from the URL, are available through the @params hash. So an action that was performed through /weblog/list?category=All&limit=5 will include { “category” => “All”, “limit” => 5 } in @params.

It’s also possible to construct multi-dimensional parameter hashes by specifying keys using brackets, such as:

<input type="text" name="post[name]" value="david">
<input type="text" name="post[address]" value="hyacintvej">

A request stemming from a form holding these inputs will include { “post” # => { “name” => “david”, “address” => “hyacintvej” } }. If the address input had been named “post[street]”, the @params would have included { “post” => { “address” => { “street” => “hyacintvej” } } }. There’s no limit to the depth of the nesting.

Sessions

Sessions allows you to store objects in memory between requests. This is useful for objects that are not yet ready to be persisted, such as a Signup object constructed in a multi-paged process, or objects that don’t change much and are needed all the time, such as a User object for a system that requires login. The session should not be used, however, as a cache for objects where it’s likely they could be changed unknowingly. It’s usually too much work to keep it all synchronized – something databases already excel at.

You can place objects in the session by using the @session hash:

@session["person"] = Person.authenticate(user_name, password)

And retrieved again through the same hash:

Hello #{@session["person"]}

Any object can be placed in the session (as long as it can be Marshalled). But remember that 1000 active sessions each storing a 50kb object could lead to a 50MB memory overhead. In other words, think carefully about size and caching before resorting to the use of the session.

Responses

Each action results in a response, which holds the headers and document to be sent to the user’s browser. The actual response object is generated automatically through the use of renders and redirects, so it’s normally nothing you’ll need to be concerned about.

Renders

Action Controller sends content to the user by using one of five rendering methods. The most versatile and common is the rendering of a template. Included in the Action Pack is the Action View, which enables rendering of ERb templates. It’s automatically configured. The controller passes objects to the view by assigning instance variables:

def show
  @post = Post.find(@params["id"])
end

Which are then automatically available to the view:

Title: <%= @post.title %>

You don’t have to rely on the automated rendering. Especially actions that could result in the rendering of different templates will use the manual rendering methods:

def search
  @results = Search.find(@params["query"])
  case @results
    when 0 then render "weblog/no_results"
    when 1 then render_action "show"
    when 2..10 then render_action "show_many"
  end
end

Read more about writing ERb and Builder templates in classes/ActionView/Base.html.

Redirects

Redirecting is what actions that update the model do when they’re done. The save_post method shouldn’t be responsible for also showing the post once it’s saved – that’s the job for show_post. So once save_post has completed its business, it’ll redirect to show_post. All redirects are external, which means that when the user refreshes his browser, it’s not going to save the post again, but rather just show it one more time.

This sounds fairly simple, but the redirection is complicated by the quest for a phenomenon known as “pretty urls”. Instead of accepting the dreadful beings that is “weblog_controller?action=show&post_id=5”, Action Controller goes out of its way to represent the former as “/weblog/show/5”. And this is even the simple case. As an example of a more advanced pretty url consider “/library/books/ISBN/0743536703/show”, which can be mapped to books_controller?action=show&type=ISBN&id=0743536703.

Redirects work by rewriting the URL of the current action. So if the show action was called by “/library/books/ISBN/0743536703/show”, we can redirect to an edit action simply by doing redirect_to(:action => "edit"), which could throw the user to “/library/books/ISBN/0743536703/edit”. Naturally, you’ll need to setup the .htaccess (or other means of URL rewriting for the web server) to point to the proper controller and action in the first place, but once you have, it can be rewritten with ease.

Let’s consider a bunch of examples on how to go from “/library/books/ISBN/0743536703/edit” to somewhere else:

redirect_to(:action => "show", :action_prefix => "XTC/123") =>
  "http://www.singlefile.com/library/books/XTC/123/show"

redirect_to(:path_params => {"type" => "EXBC"}) =>
  "http://www.singlefile.com/library/books/EXBC/0743536703/show"

redirect_to(:controller => "settings") => 
  "http://www.singlefile.com/library/settings/"

For more examples of redirecting options, have a look at the unit test in test/controller/url_test.rb. It’s very readable and will give you an excellent understanding of the different options and what they do.

Environments

Action Controller works out of the box with CGI, FastCGI, and mod_ruby. CGI and mod_ruby controllers are triggered just the same using:

WeblogController.process_cgi

FastCGI controllers are triggered using:

FCGI.each_cgi{ |cgi| WeblogController.process_cgi(cgi) }

Constant Summary collapse

DEFAULT_RENDER_STATUS_CODE = 
"200 OK"
DEFAULT_SEND_FILE_OPTIONS = 
{
  :type         => 'application/octet_stream',
  :disposition  => 'attachment',
  :stream       => true, 
  :buffer_size  => 4096
}
@@view_controller_internals =

Determines whether the view has access to controller internals @request, @response, @session, and @template. By default, it does.

true
@@consider_all_requests_local =

All requests are considered local by default, so everyone will be exposed to detailed debugging screens on errors. When the application is ready to go public, this should be set to false, and the protected method local_request? should instead be implemented in the controller to determine when debugging screens should be shown.

true

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from ClassInheritableAttributes

append_features

Instance Attribute Details

#assigns ⇒ Object

Holds the hash of variables that are passed on to the template class to be made available to the view. This hash is generated by taking a snapshot of all the instance variables in the current scope just before a template is rendered.



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# File 'lib/action_controller/base.rb', line 234

def assigns
  @assigns
end

#headers ⇒ Object

Holds a hash of header names and values. Accessed like @headers["Cache-Control"] to get the value of the Cache-Control directive. Values should always be specified as strings.



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# File 'lib/action_controller/base.rb', line 230

def headers
  @headers
end

#params ⇒ Object

Holds a hash of all the GET, POST, and Url parameters passed to the action. Accessed like @params["post_id"] to get the post_id. No type casts are made, so all values are returned as strings.



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# File 'lib/action_controller/base.rb', line 216

def params
  @params
end

#request ⇒ Object

Holds the request object that’s primarily used to get environment variables through access like @request.env["REQUEST_URI"].



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# File 'lib/action_controller/base.rb', line 212

def request
  @request
end

#response ⇒ Object

Holds the response object that’s primarily used to set additional HTTP headers through access like @response.headers["Cache-Control"] = "no-cache". Can also be used to access the final body HTML after a template has been rendered through @response.body – useful for after_filters that wants to manipulate the output, such as a OutputCompressionFilter.



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# File 'lib/action_controller/base.rb', line 222

def response
  @response
end

#session ⇒ Object

Holds a hash of objects in the session. Accessed like @session["person"] to get the object tied to the “person” key. The session will hold any type of object as values, but the key should be a string.



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# File 'lib/action_controller/base.rb', line 226

def session
  @session
end

Class Method Details

.controller_class_name ⇒ Object

Converts the class name from something like “OneModule::TwoModule::NeatController” to “NeatController”.



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# File 'lib/action_controller/base.rb', line 243

def controller_class_name
  Inflector.demodulize(name)
end

.controller_name ⇒ Object

Converts the class name from something like “OneModule::TwoModule::NeatController” to “neat”.



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# File 'lib/action_controller/base.rb', line 248

def controller_name
  Inflector.underscore(controller_class_name.sub(/Controller/, ""))
end

.process(request, response) ⇒ Object

Factory for the standard create, process loop where the controller is discarded after processing.



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# File 'lib/action_controller/base.rb', line 238

def process(request, response) #:nodoc:
  new.process(request, response)
end

.process_cgi(cgi = CGI.new, session_options = {}) ⇒ Object

Process a request extracted from an CGI object and return a response. Pass false as session_options to disable sessions (large performance increase if sessions are not needed). The session_options are the same as for CGI::Session:

  • :database_manager - standard options are CGI::Session::FileStore, CGI::Session::MemoryStore, and CGI::Session::PStore (default). Additionally, there is CGI::Session::DRbStore and CGI::Session::ActiveRecordStore. Read more about these in lib/action_controller/session.

  • :session_key - the parameter name used for the session id. Defaults to ‘_session_id’.

  • :session_id - the session id to use. If not provided, then it is retrieved from the session_key parameter of the request, or automatically generated for a new session.

  • :new_session - if true, force creation of a new session. If not set, a new session is only created if none currently exists. If false, a new session is never created, and if none currently exists and the session_id option is not set, an ArgumentError is raised.

  • :session_expires - the time the current session expires, as a Time object. If not set, the session will continue indefinitely.

  • :session_domain - the hostname domain for which this session is valid. If not set, defaults to the hostname of the server.

  • :session_secure - if true, this session will only work over HTTPS.

  • :session_path - the path for which this session applies. Defaults to the directory of the CGI script.



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# File 'lib/action_controller/cgi_process.rb', line 26

def self.process_cgi(cgi = CGI.new, session_options = {}) 
  new.process_cgi(cgi, session_options)
end

.process_test(request) ⇒ Object

Process a test request called with a TestRequest object.



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# File 'lib/action_controller/test_process.rb', line 7

def self.process_test(request)
  new.process_test(request)
end

Instance Method Details

#action_name ⇒ Object

Returns the name of the action this controller is processing.



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# File 'lib/action_controller/base.rb', line 342

def action_name
  @params["action"] || "index"
end

#controller_class_name ⇒ Object

Converts the class name from something like “OneModule::TwoModule::NeatController” to “NeatController”.



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# File 'lib/action_controller/base.rb', line 332

def controller_class_name
  self.class.controller_class_name
end

#controller_name ⇒ Object

Converts the class name from something like “OneModule::TwoModule::NeatController” to “neat”.



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# File 'lib/action_controller/base.rb', line 337

def controller_name
  self.class.controller_name
end

#module_name ⇒ Object 



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# File 'lib/action_controller/base.rb', line 327

def module_name
  @params["module"]
end

#process(request, response, method = :perform_action, *arguments) ⇒ Object

Extracts the action_name from the request parameters and performs that action.



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# File 'lib/action_controller/base.rb', line 255

def process(request, response, method = :perform_action, *arguments) #:nodoc:
  initialize_template_class(response)
  assign_shortcuts(request, response)
  initialize_current_url

  log_processing unless logger.nil?
  send(method, *arguments)
  close_session

  return @response
end

#process_cgi(cgi, session_options = {}) ⇒ Object

:nodoc:



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# File 'lib/action_controller/cgi_process.rb', line 30

def process_cgi(cgi, session_options = {}) #:nodoc:
  process(CgiRequest.new(cgi, session_options), CgiResponse.new(cgi)).out
end

#process_test(request) ⇒ Object

:nodoc:



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# File 'lib/action_controller/test_process.rb', line 11

def process_test(request) #:nodoc:
  process(request, TestResponse.new)
end

#url_for(options = {}, *parameters_for_method_reference) ⇒ Object

Returns an URL that has been rewritten according to the hash of options (for doing a complete redirect, use redirect_to). The valid keys in options are specified below with an example going from “/library/books/ISBN/0743536703/show” (mapped to books_controller?action=show&type=ISBN&id=0743536703):

         .---> controller      .--> action
/library/books/ISBN/0743536703/show
'------>      '--------------> action_prefix
 controller_prefix (or module)

  • :controller_prefix - specifies the string before the controller name, which would be “/library” for the example. Called with “/shop” gives “/shop/books/ISBN/0743536703/show”.

  • :module - serves as a alias to :controller_prefix (overwrites :controller_prefix unless its nil)

  • :controller - specifies a new controller and clears out everything after the controller name (including the action, the pre- and suffix, and all params), so called with “settings” gives “/library/settings/”.

  • :action_prefix - specifies the string between the controller name and the action name, which would be “/ISBN/0743536703” for the example. Called with “/XTC/123/” gives “/library/books/XTC/123/show”.

  • :action - specifies a new action, so called with “edit” gives “/library/books/ISBN/0743536703/edit”

  • :action_suffix - specifies the string after the action name, which would be empty for the example. Called with “/detailed” gives “/library/books/ISBN/0743536703/detailed”.

  • :path_params - specifies a hash that contains keys mapping to the request parameter names. In the example, { “type” => “ISBN”, “id” => “0743536703” } would be the path_params. It serves as another way of replacing part of the action_prefix or action_suffix. So passing { “type” => “XTC” } would give “/library/books/XTC/0743536703/show”.

  • :id - shortcut where “:id => 5” can be used instead of specifying :path_params => { “id” => 5 }. Called with “123” gives “/library/books/ISBN/123/show”.

  • :params - specifies a hash that represents the regular request parameters, such as { “cat” => 1, “origin” => “there”} that would give “?cat=1&origin=there”. Called with { “temporary” => 1 } in the example would give “/library/books/ISBN/0743536703/show?temporary=1”

  • :anchor - specifies the anchor name to be appended to the path. Called with “x14” would give “/library/books/ISBN/0743536703/show#x14”

  • :only_path - if true, returns the absolute URL (omitting the protocol, host name, and port).

Naturally, you can combine multiple options in a single redirect. Examples:

redirect_to(:controller_prefix => "/shop", :controller => "settings")
redirect_to(:controller_prefix => false, :controller => "settings") # breaks out of the current controller_prefix
redirect_to(:action => "edit", :id => 3425)
redirect_to(:action => "edit", :path_params => { "type" => "XTC" }, :params => { "temp" => 1})
redirect_to(:action => "publish", :action_prefix => "/published", :anchor => "x14")

Instead of passing an options hash, you can also pass a method reference in the form of a symbol. Consider this example:

class WeblogController < ActionController::Base
  def update
    # do some update
    redirect_to :dashboard_url
  end

  protected
    def dashboard_url
      url_for :controller => (@project.active? ? "project" : "account"), :action => "dashboard"
    end
end



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# File 'lib/action_controller/base.rb', line 319

def url_for(options = {}, *parameters_for_method_reference) #:doc:
  case options
    when String then options
    when Symbol then send(options, *parameters_for_method_reference)
    when Hash   then @url.rewrite(rewrite_options(options))
  end
end