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 routes.rb.
Tip: If you need to generate URLs from your models or some other place, then ActionController::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 ActionController::UrlFor under the hood. And in particular, they use the ActionController::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 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: 'www.example.com')
# => "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
:host
argument.
For convenience reasons, mailers provide a shortcut for
ActionController::UrlFor#url_for. So within mailers, you only have to type
url_for
instead of 'ActionController::UrlFor#url_for'
in full. However, mailers don't have hostname information, and you
still have to provide the :host
argument or set the default
host that will be used in all mailers using the configuration option
config.action_mailer.default_url_options
. For more information
on #url_for in mailers read 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_path(self)
end
end
User.find(1).base_uri # => "/users/1"
Generate a url based on the options provided, default_url_options and the routes defined in routes.rb. The following options are supported:
-
:only_path
- If true, the relative url is returned. Defaults tofalse
. -
: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 viadefault_url_options
. -
:subdomain
- Specifies the subdomain of the link, using thetld_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 thetld_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 toActionDispatch::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. -
: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: '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'
url_for controller: 'tasks', action: 'testing', host: 'somehost.org', script_name: "/myapp"
# => 'http://somehost.org/myapp/tasks/testing'
url_for controller: 'tasks', action: 'testing', host: 'somehost.org', 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.
Hook overridden in controller to add request information with `default_url_options`. Application logic should not go into url_options.