url_for.rb

module AbstractController
  # In <b>routes.rb</b> one defines URL-to-controller mappings, but the reverse
  # is also possible: an URL can be generated from one of your routing definitions.
  # URL generation functionality is centralized in this module.
  #
  # See AbstractController::Routing and AbstractController::Resources for general
  # information about routing and routes.rb.
  #
  # <b>Tip:</b> If you need to generate URLs from your models or some other place,
  # then AbstractController::UrlFor is what you're looking for. Read on for
  # an introduction.
  #
  # == URL generation from parameters
  #
  # As you may know, some functions - such as AbstractController::Base#url_for
  # and ActionView::Helpers::UrlHelper#link_to, can generate URLs given a set
  # of parameters. For example, you've probably had the chance to write code
  # like this in one of your views:
  #
  #   <%= link_to('Click here', :controller => 'users',
  #           :action => 'new', :message => 'Welcome!') %>
  #
  #   #=> Generates a link to: /users/new?message=Welcome%21
  #
  # link_to, and all other functions that require URL generation functionality,
  # actually use AbstractController::UrlFor under the hood. And in particular,
  # they use the AbstractController::UrlFor#url_for method. One can generate
  # the same path as the above example by using the following code:
  #
  #   include UrlFor
  #   url_for(:controller => 'users',
  #           :action => 'new',
  #           :message => 'Welcome!',
  #           :only_path => true)
  #   # => "/users/new?message=Welcome%21"
  #
  # Notice the <tt>:only_path => true</tt> part. This is because UrlFor has no
  # information about the website hostname that your Rails app is serving. So if you
  # want to include the hostname as well, then you must also pass the <tt>:host</tt>
  # argument:
  #
  #   include UrlFor
  #   url_for(:controller => 'users',
  #           :action => 'new',
  #           :message => 'Welcome!',
  #           :host => 'www.example.com')        # Changed this.
  #   # => "http://www.example.com/users/new?message=Welcome%21"
  #
  # By default, all controllers and views have access to a special version of url_for,
  # that already knows what the current hostname is. So if you use url_for in your
  # controllers or your views, then you don't need to explicitly pass the <tt>:host</tt>
  # argument.
  #
  # For convenience reasons, mailers provide a shortcut for AbstractController::UrlFor#url_for.
  # So within mailers, you only have to type 'url_for' instead of 'AbstractController::UrlFor#url_for'
  # in full. However, mailers don't have hostname information, and what's why you'll still
  # have to specify the <tt>:host</tt> argument when generating URLs in mailers.
  #
  #
  # == URL generation for named routes
  #
  # UrlFor also allows one to access methods that have been auto-generated from
  # named routes. For example, suppose that you have a 'users' resource in your
  # <b>routes.rb</b>:
  #
  #   map.resources :users
  #
  # This generates, among other things, the method <tt>users_path</tt>. By default,
  # this method is accessible from your controllers, views and mailers. If you need
  # to access this auto-generated method from other places (such as a model), then
  # you can do that by including AbstractController::UrlFor in your class:
  #
  #   class User < ActiveRecord::Base
  #     include AbstractController::UrlFor
  #
  #     def base_uri
  #       user_path(self)
  #     end
  #   end
  #
  #   User.find(1).base_uri # => "/users/1"
  #
  module UrlFor
    extend ActiveSupport::Concern

    included do
      ActionController::Routing::Routes.install_helpers(self)
      extlib_inheritable_accessor :default_url_options,
                                  :instance_writer => false, :instance_reader => false
      self.default_url_options ||= {}
    end

    # Overwrite to implement a number of default options that all url_for-based methods will use. The default options should come in
    # the form of a hash, just like the one you would use for url_for directly. Example:
    #
    #   def default_url_options(options)
    #     { :project => @project.active? ? @project.url_name : "unknown" }
    #   end
    #
    # As you can infer from the example, this is mostly useful for situations where you want to centralize dynamic decisions about the
    # urls as they stem from the business domain. Please note that any individual url_for call can always override the defaults set
    # by this method.
    def default_url_options(options = nil)
      self.class.default_url_options
    end

    def rewrite_options(options) #:nodoc:
      if options.delete(:use_defaults) != false && (defaults = default_url_options(options))
        defaults.merge(options)
      else
        options
      end
    end

    # Generate a url based on the options provided, default_url_options and the
    # routes defined in routes.rb.  The following options are supported:
    #
    # * <tt>:only_path</tt> - If true, the relative url is returned. Defaults to +false+.
    # * <tt>:protocol</tt> - The protocol to connect to. Defaults to 'http'.
    # * <tt>:host</tt> - Specifies the host the link should be targeted at.
    #   If <tt>:only_path</tt> is false, this option must be
    #   provided either explicitly, or via +default_url_options+.
    # * <tt>:port</tt> - Optionally specify the port to connect to.
    # * <tt>:anchor</tt> - An anchor name to be appended to the path.
    # * <tt>:skip_relative_url_root</tt> - If true, the url is not constructed using the
    #   +relative_url_root+ set in AbstractController::Base.relative_url_root.
    # * <tt>:trailing_slash</tt> - If true, adds a trailing slash, as in "/archive/2009/"
    #
    # Any other key (<tt>:controller</tt>, <tt>:action</tt>, etc.) given to
    # +url_for+ is forwarded to the Routes module.
    #
    # Examples:
    #
    #    url_for :controller => 'tasks', :action => 'testing', :host=>'somehost.org', :port=>'8080'    # => 'http://somehost.org:8080/tasks/testing'
    #    url_for :controller => 'tasks', :action => 'testing', :host=>'somehost.org', :anchor => 'ok', :only_path => true    # => '/tasks/testing#ok'
    #    url_for :controller => 'tasks', :action => 'testing', :trailing_slash=>true  # => 'http://somehost.org/tasks/testing/'
    #    url_for :controller => 'tasks', :action => 'testing', :host=>'somehost.org', :number => '33'  # => 'http://somehost.org/tasks/testing?number=33'
    def url_for(options = {})
      options ||= {}
      case options
        when String
          options
        when Hash
          _url_rewriter.rewrite(rewrite_options(options))
        else
          polymorphic_url(options)
      end
    end

  protected

    def _url_rewriter
      ActionController::UrlRewriter
    end
  end
end