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| -rw-r--r-- | actionpack/lib/action_controller/base.rb | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/actionpack/lib/action_controller/base.rb b/actionpack/lib/action_controller/base.rb index 9dfffced75..165bf089c0 100644 --- a/actionpack/lib/action_controller/base.rb +++ b/actionpack/lib/action_controller/base.rb @@ -1,6 +1,169 @@ require "action_controller/log_subscriber" module ActionController + # Action Controllers are the core of a web request in \Rails. They are made up of one or more actions that are executed + # on request and then either render a template or redirect 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 \Rails Routes. + # + # By default, only the ApplicationController in a \Rails application inherits from <tt>ActionController::Base</tt>. All other + # controllers in turn inherit from ApplicationController. This gives you one class to configure things such as + # request forgery protection and filtering of sensitive request parameters. + # + # A sample controller could look like this: + # + # class PostsController < ApplicationController + # def index + # @posts = Post.all + # end + # + # def create + # @post = Post.create params[:post] + # redirect_to posts_path + # end + # end + # + # Actions, by default, render a template in the <tt>app/views</tt> directory corresponding to the name of the controller and action + # after executing code in the action. For example, the +index+ action of the PostsController would render the + # template <tt>app/views/posts/index.erb</tt> by default after populating the <tt>@posts</tt> instance variable. + # + # Unlike index, the create action will not render a template. After performing its main purpose (creating a + # new post), it initiates a redirect instead. This redirect works by returning an external + # "302 Moved" HTTP response that takes the user to the index action. + # + # These two methods represent the two basic action archetypes used in Action Controllers. Get-and-show and do-and-redirect. + # Most actions are variations of these themes. + # + # == Requests + # + # For every request, the router determines the value of the +controller+ and +action+ keys. These determine which controller + # and action are called. 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 accessor methods. Then the action is performed. + # + # The full request object is available via the request accessor and is primarily used to query for HTTP headers: + # + # def server_ip + # location = request.env["SERVER_ADDR"] + # render :text => "This server hosted at #{location}" + # end + # + # == Parameters + # + # All request parameters, whether they come from a GET or POST request, or from the URL, are available through the params method + # which returns a hash. For example, an action that was performed through <tt>/posts?category=All&limit=5</tt> will include + # <tt>{ "category" => "All", "limit" => 5 }</tt> 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 <tt>{ "post" => { "name" => "david", "address" => "hyacintvej" } }</tt>. + # If the address input had been named "post[address][street]", the params would have included + # <tt>{ "post" => { "address" => { "street" => "hyacintvej" } } }</tt>. There's no limit to the depth of the nesting. + # + # == Sessions + # + # Sessions allows you to store objects in 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 <tt>session</tt> method, which accesses a hash: + # + # session[:person] = Person.authenticate(user_name, password) + # + # And retrieved again through the same hash: + # + # Hello #{session[:person]} + # + # For removing objects from the session, you can either assign a single key to +nil+: + # + # # removes :person from session + # session[:person] = nil + # + # or you can remove the entire session with +reset_session+. + # + # Sessions are stored by default in a browser cookie that's cryptographically signed, but unencrypted. + # This prevents the user from tampering with the session but also allows him to see its contents. + # + # Do not put secret information in cookie-based sessions! + # + # Other options for session storage: + # + # * ActiveRecord::SessionStore - Sessions are stored in your database, which works better than PStore with multiple app servers and, + # unlike CookieStore, hides your session contents from the user. To use ActiveRecord::SessionStore, set + # + # config.action_controller.session_store = :active_record_store + # + # in your <tt>config/environment.rb</tt> and run <tt>rake db:sessions:create</tt>. + # + # == 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 and requires no user intervention. + # + # == 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 :action => "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 ActionView::Base. + # + # == Redirects + # + # Redirects are used to move from one action to another. For example, after a <tt>create</tt> action, which stores a blog entry to a database, + # we might like to show the user the new entry. Because we're following good DRY principles (Don't Repeat Yourself), we're going to reuse (and redirect to) + # a <tt>show</tt> action that we'll assume has already been created. The code might look like this: + # + # def create + # @entry = Entry.new(params[:entry]) + # if @entry.save + # # The entry was saved correctly, redirect to show + # redirect_to :action => 'show', :id => @entry.id + # else + # # things didn't go so well, do something else + # end + # end + # + # In this case, after saving our new entry to the database, the user is redirected to the <tt>show</tt> method which is then executed. + # + # == Calling multiple redirects or renders + # + # An action may contain only a single render or a single redirect. Attempting to try to do either again will result in a DoubleRenderError: + # + # def do_something + # redirect_to :action => "elsewhere" + # render :action => "overthere" # raises DoubleRenderError + # end + # + # If you need to redirect on the condition of something, then be sure to add "and return" to halt execution. + # + # def do_something + # redirect_to(:action => "elsewhere") and return if monkeys.nil? + # render :action => "overthere" # won't be called if monkeys is nil + # end + # class Base < Metal abstract! |