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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:
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"
Instance Method Summary collapse
- #initialize ⇒ Object
#url_for(options = nil) ⇒ Object
Generate a url based on the options provided, default_url_options and the routes defined in routes.rb.
#url_options ⇒ Object
Hook overridden in controller to add request information with `default_url_options`.
Methods included from
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Methods included from
Instance Method Details
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# File 'actionpack/lib/action_dispatch/routing/url_for.rb', line 104 def initialize(*) @_routes = nil super end
#url_for(options = nil) ⇒
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 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.
: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.
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# File 'actionpack/lib/action_dispatch/routing/url_for.rb', line 166 def url_for( = nil) case when nil _routes.url_for(.symbolize_keys) when Hash route_name = .delete :use_route _routes.url_for(.symbolize_keys.reverse_merge!(), route_name) when ActionController::Parameters unless .permitted? raise ArgumentError.new("Generating an URL from non sanitized request parameters is insecure!") end route_name = .delete :use_route _routes.url_for(.to_h.symbolize_keys. reverse_merge!(), route_name) when String when Symbol HelperMethodBuilder.url.handle_string_call self, when Array components = .dup polymorphic_url(components, components.) when Class HelperMethodBuilder.url.handle_class_call self, else HelperMethodBuilder.url.handle_model_call self, end end
Hook overridden in controller to add request information with `default_url_options`. Application logic should not go into url_options.
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# File 'actionpack/lib/action_dispatch/routing/url_for.rb', line 112 def end