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Action Dispatch Routing UrlFor

In config/routes.rb you define URL-to-controller mappings, but the reverse is also possible: a URL can be generated from one of your routing definitions. URL generation functionality is centralized in this module.

See ActionDispatch::Routing for general information about routing and config/routes.rb.

Tip: If you need to generate URLs from your models or some other place, then ActionDispatch::Routing::UrlFor is what you’re looking for. Read on for an introduction. In general, this module should not be included on its own, as it is usually included by url_helpers (as in Rails.application.routes.url_helpers).

URL generation from parameters

As you may know, some functions, such as ActionController::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!') %>
# => <a href="/users/new?message=Welcome%21">Click here</a>

link_to, and all other functions that require URL generation functionality, actually use ActionDispatch::Routing::UrlFor under the hood. And in particular, they use the ActionDispatch::Routing::UrlFor#url_for method. One can generate the same path as the above example by using the following code:

include ActionDispatch::Routing::UrlFor
url_for(controller: 'users',
        action: 'new',
        message: 'Welcome!',
        only_path: true)
# => "/users/new?message=Welcome%21"

Notice the only_path: true 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 :host argument:

include UrlFor
url_for(controller: 'users',
        action: 'new',
        message: 'Welcome!',
        host: '')
# => ""

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 :host argument.

For convenience, mailers also include ActionDispatch::Routing::UrlFor. So within mailers, you can use url_for. However, mailers cannot access incoming web requests in order to derive hostname information, so you have to provide the :host option or set the default host using default_url_options. For more information on url_for in mailers see the ActionMailer::Base documentation.

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 config/routes.rb:

resources :users

This generates, among other things, the method users_path. 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 Rails.application.routes.url_helpers in your class:

class User < ActiveRecord::Base
  include Rails.application.routes.url_helpers

  def base_uri

User.find(1).base_uri # => "/users/1"
Included Modules

Class Public methods


# File actionpack/lib/action_dispatch/routing/url_for.rb, line 108
def initialize(...)
  @_routes = nil

Instance Public methods

route_for(name, *args)

Allows calling direct or regular named route.

resources :buckets

direct :recordable do |recording|
  route_for(:bucket, recording.bucket)

direct :threadable do |threadable|
  route_for(:recordable, threadable.parent)

This maintains the context of the original caller on whether to return a path or full URL, e.g:

threadable_path(threadable)  # => "/buckets/1"
threadable_url(threadable)   # => ""
# File actionpack/lib/action_dispatch/routing/url_for.rb, line 217
def route_for(name, *args)
  public_send(:"#{name}_url", *args)

url_for(options = nil)

Generate a URL based on the options provided, default_url_options, and the routes defined in config/routes.rb. The following options are supported:

  • :only_path - If true, the relative URL is returned. Defaults to false.

  • :protocol - The protocol to connect to. Defaults to "http".

  • :host - Specifies the host the link should be targeted at. If :only_path is false, this option must be provided either explicitly, or via default_url_options.

  • :subdomain - Specifies the subdomain of the link, using the tld_length to split the subdomain from the host. If false, removes all subdomains from the host part of the link.

  • :domain - Specifies the domain of the link, using the tld_length to split the domain from the host.

  • :tld_length - Number of labels the TLD id composed of, only used if :subdomain or :domain are supplied. Defaults to ActionDispatch::Http::URL.tld_length, which in turn defaults to 1.

  • :port - Optionally specify the port to connect to.

  • :anchor - An anchor name to be appended to the path.

  • :params - The query parameters to be appended to the path.

  • :path_params - The query parameters that will only be used for the named dynamic segments of path. If unused, they will be discarded.

  • :trailing_slash - If true, adds a trailing slash, as in "/archive/2009/".

  • :script_name - Specifies application path relative to domain root. If provided, prepends application path.

Any other key (:controller, :action, etc.) given to url_for is forwarded to the Routes module.

url_for controller: 'tasks', action: 'testing', host: '', port: '8080'
# => ''
url_for controller: 'tasks', action: 'testing', host: '', anchor: 'ok', only_path: true
# => '/tasks/testing#ok'
url_for controller: 'tasks', action: 'testing', trailing_slash: true
# => ''
url_for controller: 'tasks', action: 'testing', host: '', number: '33'
# => ''
url_for controller: 'tasks', action: 'testing', host: '', script_name: "/myapp"
# => ''
url_for controller: 'tasks', action: 'testing', host: '', script_name: "/myapp", only_path: true
# => '/myapp/tasks/testing'

Missing routes keys may be filled in from the current request’s parameters (e.g. :controller, :action, :id, and any other parameters that are placed in the path). Given that the current action has been reached through GET /users/1:

url_for(only_path: true)                        # => '/users/1'
url_for(only_path: true, action: 'edit')        # => '/users/1/edit'
url_for(only_path: true, action: 'edit', id: 2) # => '/users/2/edit'

Notice that no :id parameter was provided to the first url_for call and the helper used the one from the route’s path. Any path parameter implicitly used by url_for can always be overwritten like shown on the last url_for calls.

# File actionpack/lib/action_dispatch/routing/url_for.rb, line 173
def url_for(options = nil)


Hook overridden in controller to add request information with default_url_options. Application logic should not go into url_options.

# File actionpack/lib/action_dispatch/routing/url_for.rb, line 116
def url_options

Instance Protected methods


# File actionpack/lib/action_dispatch/routing/url_for.rb, line 222
def optimize_routes_generation?
  _routes.optimize_routes_generation? && default_url_options.empty?

Instance Private methods


# File actionpack/lib/action_dispatch/routing/url_for.rb, line 234
def _routes_context # :doc:


# File actionpack/lib/action_dispatch/routing/url_for.rb, line 227
def _with_routes(routes) # :doc:
  old_routes, @_routes = @_routes, routes
  @_routes = old_routes