The Rails router recognizes URLs and dispatches them to a controller's action. It can also generate paths and URLs, avoiding the need to hardcode strings in your views.
Resource routing allows you to quickly declare all of the common routes for a given resourceful controller. Instead of declaring separate routes for your +index+, +show+, +new+, +edit+, +create+, +update+ and +destroy+ actions, a resourceful route declares them in a single line of code.
Browsers request pages from Rails by making a request for a URL using a specific HTTP method, such as +GET+, +POST+, +PUT+ and +DELETE+. Each method is a request to perform an operation on the resource. A resource route maps a number of related request to the actions in a single controller.
In Rails, a resourceful route provides a mapping between HTTP verbs and URLs and controller actions. By convention, each action also maps to particular CRUD operations in a database. A single entry in the routing file, such as
Each of these helpers has a corresponding +_url+ helper (such as +photos_url+) which returns the same path prefixed with the current host, port and path prefix.
Sometimes, you have a resource that clients always look up without referencing an ID. A common example, +/profile+ always shows the profile of the currently logged in user. In this case, you can use a singular resource to map +/profile+ (rather than +/profile/:id+) to the +show+ action.
NOTE: Because you might want to use the same controller for a singular route (+/account+) and a plural route (+/accounts/45+), singular resources map to plural controllers.
You may wish to organize groups of controllers under a namespace. Most commonly, you might group a number of administrative controllers under an +Admin::+ namespace. You would place these controllers under the +app/controllers/admin+ directory, and you can group them together in your router:
In each of these cases, the named routes remain the same as if you did not use +scope+. In the last case, the following paths map to +PostsController+:
This will also create routing helpers such as +magazine_ads_url+ and +edit_magazine_ad_path+. These helpers take an instance of Magazine as the first parameter (+magazine_ads_url(@magazine)+).
The corresponding route helper would be +publisher_magazine_photo_url+, requiring you to specify objects at all three levels. Indeed, this situation is confusing enough that a popular "article":http://weblog.jamisbuck.org/2007/2/5/nesting-resources by Jamis Buck proposes a rule of thumb for good Rails design:
In addition to using the routing helpers, Rails can also create paths and URLs from an array of parameters. For example, suppose you have this set of routes:
In this case, Rails will see that +@magazine+ is a +Magazine+ and +@ad+ is an +Ad+ and will therefore use the +magazine_ad_path+ helper. In helpers like +link_to+, you can specify just the object in place of the full +url_for+ call:
You are not limited to the seven routes that RESTful routing creates by default. If you like, you may add additional routes that apply to the collection or individual members of the collection.
This will recognize +/photos/1/preview+ with GET, and route to the +preview+ action of +PhotosController+. It will also create the +preview_photo_url+ and +preview_photo_path+ helpers.
Within the block of member routes, each route name specifies the HTTP verb that it will recognize. You can use +get+, +put+, +post+, or +delete+ here. If you don't have multiple +member+ routes, you can also pass +:on+ to a route, eliminating the block:
This will enable Rails to recognize paths such as +/photos/search+ with GET, and route to the +search+ action of +PhotosController+. It will also create the +search_photos_url+ and +search_photos_path+ route helpers.
If you find yourself adding many extra actions to a resourceful route, it's time to stop and ask yourself whether you're disguising the presence of another resource.
In addition to resource routing, Rails has powerful support for routing arbitrary URLs to actions. Here, you don't get groups of routes automatically generated by resourceful routing. Instead, you set up each route within your application separately.
While you should usually use resourceful routing, there are still many places where the simpler routing is more appropriate. There's no need to try to shoehorn every last piece of your application into a resourceful framework if that's not a good fit.
In particular, simple routing makes it very easy to map legacy URLs to new Rails actions.
When you set up a regular route, you supply a series of symbols that Rails maps to parts of an incoming HTTP request. Two of these symbols are special: +:controller+ maps to the name of a controller in your application, and +:action+ maps to the name of an action within that controller. For example, consider one of the default Rails routes:
If an incoming request of +/photos/show/1+ is processed by this route (because it hasn't matched any previous route in the file), then the result will be to invoke the +show+ action of the +PhotosController+, and to make the final parameter +"1"+ available as +params[:id]+. This route will also route the incoming request of +/photos+ to +PhotosController+, since +:action+ and +:id+ are optional parameters, denoted by parentheses.
You can set up as many dynamic segments within a regular route as you like. Anything other than +:controller+ or +:action+ will be available to the action as part of +params+. If you set up this route:
An incoming path of +/photos/show/1/2+ will be dispatched to the +show+ action of the +PhotosController+. +params[:id]+ will be +"1"+, and +params[:user_id]+ will be +"2"+.
NOTE: You can't use +namespace+ or +:module+ with a +:controller+ path segment. If you need to do this then use a constraint on :controller that matches the namespace you require. e.g:
<ruby>
match ':controller(/:action(/:id))', :controller => /admin\/[^\/]+/
This route would respond to paths such as +/photos/show/1/with_user/2+. In this case, +params+ would be <tt>{ :controller => "photos", :action => "show", :id => "1", :user_id => "2" }</tt>.
An incoming path of +/photos/show/1?user_id=2+ will be dispatched to the +show+ action of the +Photos+ controller. +params+ will be <tt>{ :controller => "photos", :action => "show", :id => "1", :user_id => "2" }</tt>.
You can also define other defaults in a route by supplying a hash for the +:defaults+ option. This even applies to parameters that you do not specify as dynamic segments. For example:
match '/:id' => 'posts#show', :constraints => {:id => /^\d/}
</ruby>
However, note that you don't need to use anchors because all routes are anchored at the start.
For example, the following routes would allow for +posts+ with +to_param+ values like +1-hello-world+ that always begin with a number and +users+ with +to_param+ values like +david+ that never begin with a number to share the root namespace:
You can also constrain a route based on any method on the <a href="action_controller_overview.html#the-request-object">Request</a> object that returns a +String+.
You specify a request-based constraint the same way that you specify a segment constraint:
If you have a more advanced constraint, you can provide an object that responds to +matches?+ that Rails should use. Let's say you wanted to route all users on a blacklist to the +BlacklistController+. You could do:
Wildcard segments do not need to be last in a route. For example
<ruby>
match 'books/*section/:title' => 'books#show'
</ruby>
would match +books/some/section/last-words-a-memoir+ with +params[:section]+ equals +"some/section"+, and +params[:title]+ equals +"last-words-a-memoir"+.
Techincally a route can have even more than one wildard segment indeed, the matcher assigns segments to parameters in an intuitive way. For instance
<ruby>
match '*a/foo/*b' => 'test#index'
</ruby>
would match +zoo/woo/foo/bar/baz+ with +params[:a]+ equals +"zoo/woo"+, and +params[:b]+ equals +"bar/baz"+.
Instead of a String, like +"posts#index"+, which corresponds to the +index+ action in the +PostsController+, you can specify any <a href="rails_on_rack.html">Rack application</a> as the endpoint for a matcher.
As long as +Sprockets+ responds to +call+ and returns a <tt>[status, headers, body]</tt>, the router won't know the difference between the Rack application and an action.
NOTE: For the curious, +"posts#index"+ actually expands out to +PostsController.action(:index)+, which returns a valid Rack application.
h4. Using +root+
You can specify what Rails should route +"/"+ to with the +root+ method:
You should put the +root+ route at the end of the file.
h3. Customizing Resourceful Routes
While the default routes and helpers generated by +resources :posts+ will usually serve you well, you may want to customize them in some way. Rails allows you to customize virtually any generic part of the resourceful helpers.
h4. Specifying a Controller to Use
The +:controller+ option lets you explicitly specify a controller to use for the resource. For example:
This declaration constrains the +:id+ parameter to match the supplied regular expression. So, in this case, the router would no longer match +/photos/1+ to this route. Instead, +/photos/RR27+ would match.
You can use the +:as+ option to prefix the named route helpers that Rails generates for a route. Use this option to prevent name collisions between routes using a path scope.
By default, Rails creates routes for all seven of the default actions (index, show, new, create, edit, update, and destroy) for every RESTful route in your application. You can use the +:only+ and +:except+ options to fine-tune this behavior. The +:only+ option tells Rails to create only the specified routes:
Now, a +GET+ request to +/photos+ would succeed, but a +POST+ request to +/photos+ (which would ordinarily be routed to the +create+ action) will fail.
The +:except+ option specifies a route or list of routes that Rails should _not_ create:
TIP: If your application has many RESTful routes, using +:only+ and +:except+ to generate only the routes that you actually need can cut down on memory use and speed up the routing process.
If you want a complete list of all of the available routes in your application, run +rake routes+ command. This will print all of your routes, in the same order that they appear in +routes.rb+. For each route, you'll see:
Routes should be included in your testing strategy (just like the rest of your application). Rails offers three "built-in assertions":http://api.rubyonrails.org/classes/ActionController/Assertions/RoutingAssertions.html designed to make testing routes simpler:
The +assert_recognizes+ assertion is the inverse of +assert_generates+. It asserts that Rails recognizes the given path and routes it to a particular spot in your application.
The +assert_routing+ assertion checks the route both ways: it tests that the path generates the options, and that the options generate the path. Thus, it combines the functions of +assert_generates+ and +assert_recognizes+.
* April 10, 2010: Updated guide to remove outdated and superfluous information, and to provide information about new features, by "Yehuda Katz":http://www.yehudakatz.com
