1. The Purpose of the Rails Router

The Rails router matches incoming HTTP requests to specific controller actionsin your Rails application based on the URL path. (It can also forward to aRack application.) The router also generates path and URLhelpers based on the resources configured in the router.

1.1. Routing Incoming URLs to Code

When your Rails application receives an incoming request, it asks the router to match it to a controller action (aka method). For example, take the following incoming request:

GET /users/17

If the first matching route is:

get"/users/:id",to:"users#show"

The request is matched to theUsersController class'sshow action with{ id: '17' } in theparams hash.

Theto: option expects acontroller#action format when passed a string. Alternatively, You can pass a symbol and use theaction: option, instead ofto:. You can also pass a string without a#, in which case thecontroller: option is used instead toto:. For example:

get"/users/:id",controller:"users",action: :show

1.2. Generating Paths and URLs from Code

The Router automatically generates path and URL helper methods for your application. With these methods you can avoid hard-coded path and URL strings.

For example, theuser_path anduser_url helper methods are available when defining the following route:

get"/users/:id",to:"users#show",as:"user"

Assuming your application contains this code in the controller:

@user=User.find(params[:id])

and this in the corresponding view:

<%=link_to'User Record',user_path(@user)%>

The router will generate the path/users/17 fromuser_path(@user). Using theuser_path helper allows you to avoid having to hard-code a path in your views. This is helpful if you eventually move the route to a different URL, as you won't need to update the corresponding views.

It also generatesuser_url, which has a similar purpose. Whileuser_path generates a relative URL like/users/17,user_url generates an absolute URL such ashttps://example.com/users/17 in the above example.

1.3. Configuring the Rails Router

Routes live inconfig/routes.rb. Here is an example of what routes look like in a typical Rails application. The sections that follow will explain the different route helpers used in this file:

Rails.application.routes.drawdoresources:brands,only:[:index,:show]doresources:products,only:[:index,:show]endresource:basket,only:[:show,:update,:destroy]resolve("Basket"){route_for(:basket)}end

Since this is a regular Ruby source file, you can use all of Ruby's features (like conditionals and loops) to help you define your routes.

2. Resource Routing: the Rails Default

Resource routing allows you to quickly declare all of the common routes for a given resource controller. For example, a single call toresources declares all of the necessary routes for theindex,show,new,edit,create,update, anddestroy actions, without you having to declare each route separately.

2.1. Resources on the Web

Browsers request pages from Rails by making a request for a URL using a specific HTTP verb, such asGET,POST,PATCH,PUT, andDELETE. Each HTTP verb is a request to perform an operation on the resource. A resource route maps related requests to actions in a single controller.

When your Rails application receives an incoming request for:

DELETE /photos/17

it asks the router to map it to a controller action. If the first matching route is:

resources:photos

Rails would dispatch that request to thedestroy action on thePhotosController with{ id: '17' } inparams.

2.2. CRUD, Verbs, and Actions

In Rails, resourceful routes provide a mapping from incoming requests (acombination of HTTP verb + URL) to controller actions. By convention, eachaction generally maps to a specificCRUD operation on your data. A single entry inthe routing file, such as:

resources:photos

creates seven different routes in your application, all mapping to thePhotosController actions:

Since the router uses the HTTP verband path to match inbound requests, four URLs can map to seven different controller actions. For example, the samephotos/ path matches tophotos#index when the verb isGET andphotos#create when the verb isPOST.

2.3. Path and URL Helpers

Creating a resourceful route will also expose a number of helpers to controllers and views in your application.

For example, addingresources :photos to the route file will generate these_path helpers:

Parameters to the path helpers, such as:id above, are passed to the generated URL, such thatedit_photo_path(10) will return/photos/10/edit.

Each of these_path helpers also have a corresponding_url helper (such asphotos_url) which returns the same path prefixed with the current host, port, and path prefix.

2.4. Defining Multiple Resources at the Same Time

If you need to create routes for more than one resource, you can save a bit of typing by defining them all with a single call toresources:

resources:photos,:books,:videos

The above is a shortcut for:

resources:photosresources:booksresources:videos

2.5. Singular Resources

Sometimes, you have a resource that users expect to have only one (i.e. it does not make sense to have anindex action to list all values of that resource). In that case, you can useresource (singular) instead ofresources.

The below resourceful route creates six routes in your application, all mapping to theGeocoders controller:

resource:geocoderresolve("Geocoder"){[:geocoder]}

Here are all of the routes created for a singular resource:

A singular resourceful route generates these helpers:

• new_geocoder_path returns/geocoder/new
• edit_geocoder_path returns/geocoder/edit
• geocoder_path returns/geocoder

As with plural resources, the same helpers ending in_url will also include the host, port, and path prefix.

2.6. Controller Namespaces and Routing

In large applications, you may wish to organize groups of controllers under a namespace. For example, you may have a number of controllers under anAdmin:: namespace, which are inside theapp/controllers/admin directory. You can route to such a group by using anamespace block:

namespace:admindoresources:articlesend

ForAdmin::ArticlesController, Rails will create the following routes:

Note that in the above example all of the paths have a/admin prefix per the default convention fornamespace.

2.6.1. Using Module

If you want to route/articles (without the prefix/admin) toAdmin::ArticlesController, you can specify the module with ascope block:

scopemodule:"admin"doresources:articlesend

Another way to write the above:

resources:articles,module:"admin"

2.6.2. Using Scope

Alternatively, you can also route/admin/articles toArticlesController (without theAdmin:: module prefix). You can specify the path with ascope block:

scope"/admin"doresources:articlesend

Another way to write the above:

resources:articles,path:"/admin/articles"

For these alternatives (without/admin in path and withoutAdmin:: in module prefix), the named route helpers remain the same as if you did not usescope.

In the last case, the following paths map toArticlesController:

2.7. Nested Resources

It's common to have resources that are logically children of other resources. For example, suppose your application includes these models:

classMagazine<ApplicationRecordhas_many:adsendclassAd<ApplicationRecordbelongs_to:magazineend

Nested route declarations allow you to capture this relationship in your routing:

resources:magazinesdoresources:adsend

In addition to the routes for magazines, this declaration will also route ads to anAdsController. Here are all of the routes for the nestedads resource:

This will also create the usual path and url routing helpers such asmagazine_ads_url andedit_magazine_ad_path. Since theads resource is nested belowmagazines, The ad URLs require a magazine. The helpers can take an instance ofMagazine as the first parameter (edit_magazine_ad_path(@magazine, @ad)).

2.7.1. Limits to Nesting

You can nest resources within other nested resources if you like. For example:

resources:publishersdoresources:magazinesdoresources:photosendend

In the above example, the application would recognize paths such as:

/publishers/1/magazines/2/photos/3

The corresponding route helper would bepublisher_magazine_photo_url, requiring you to specify objects at all three levels. As you can see, deeply nested resources can become overly complex and cumbersome to maintain.

2.7.2. Shallow Nesting

One way to avoid deep nesting (as recommended above) is to generate thecollection actions scoped under the parent - so as to get a sense of thehierarchy, but to not nest the member actions. In other words, to only buildroutes with the minimal amount of information to uniquely identify the resource.

For example:

resources:articlesdoresources:comments,only:[:index,:new,:create]endresources:comments,only:[:show,:edit,:update,:destroy]

Above we use the:only option which tells Rails to create only the specified routes. This idea strikes a balance between descriptive routes and deep nesting. There is a shorthand syntax to achieve just that, via the:shallow option:

resources:articlesdoresources:comments,shallow:trueend

This will generate the exact same routes as the first example. You can also specify the:shallow option in the parent resource, in which case all of the nested resources will be shallow:

resources:articles,shallow:truedoresources:commentsresources:quotesend

The articles resource above will generate the following routes:

Theshallow method with a block creates a scope inside of which every nesting is shallow. This generates the same routes as the previous example:

shallowdoresources:articlesdoresources:commentsresources:quotesendend

There are two options that can be used withscope to customize shallow routes -:shallow_path and:shallow_prefix.

Theshallow_path option prefixes member paths with the given parameter:

scopeshallow_path:"sekret"doresources:articlesdoresources:comments,shallow:trueendend

The comments resource here will have the following routes generated for it:

The:shallow_prefix option adds the specified parameter to the_path and_url route helpers:

scopeshallow_prefix:"sekret"doresources:articlesdoresources:comments,shallow:trueendend

The comments resource here will have the following routes generated for it:

2.8. Routing Concerns

Routing concerns allow you to declare common routes that can be reused inside other resources. To define a concern, use aconcern block:

concern:commentabledoresources:commentsendconcern:image_attachabledoresources:images,only: :indexend

These concerns can be used in resources to avoid code duplication and share behavior across routes:

resources:messages,concerns: :commentableresources:articles,concerns:[:commentable,:image_attachable]

The above is equivalent to:

resources:messagesdoresources:commentsendresources:articlesdoresources:commentsresources:images,only: :indexend

You can also callconcerns in ascope ornamespace block to get the same result as above. For example:

namespace:messagesdoconcerns:commentableendnamespace:articlesdoconcerns:commentableconcerns:image_attachableend

2.9. Creating Paths and URLs from Objects

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:

resources:magazinesdoresources:adsend

When usingmagazine_ad_path, you can pass in instances ofMagazine andAd instead of the numeric IDs:

<%=link_to'Ad details',magazine_ad_path(@magazine,@ad)%>

The generated path will be something like/magazines/5/ads/42.

You can also useurl_for with an array of objects to get the above path, like this:

<%=link_to'Ad details',url_for([@magazine,@ad])%>

In this case, Rails will see that@magazine is aMagazine and@ad is anAd and will therefore use themagazine_ad_path helper. An even shorter way to write thatlink_to is to specify just the object instead of the fullurl_for call:

<%=link_to'Ad details',[@magazine,@ad]%>

If you wanted to link to just a magazine:

<%=link_to'Magazine details',@magazine%>

For other actions, you need to insert the action name as the first element of the array, foredit_magazine_ad_path:

<%=link_to'Edit Ad',[:edit,@magazine,@ad]%>

This allows you to treat instances of your models as URLs, and is a key advantage to using the resourceful style.

2.10. Adding More RESTful Routes

You are not limited to theseven routes that RESTful routing creates by default. You can add additional routes that apply to the collection or individual members of the collection.

The below sections describe adding member routes and collection routes. The termmember refers to routes acting on a single element, such asshow,update, ordestroy. The termcollection refers to routes acting on multiple, or a collection of, elements, such as theindex route.

2.10.1. Adding Member Routes

You can add amember block into the resource block like this:

resources:photosdomemberdoget"preview"endend

An incoming GET request to/photos/1/preview will route to thepreview action ofPhotosController. The resource id value will be available inparams[:id]. It will also create thepreview_photo_url andpreview_photo_path helpers.

Within themember block, each route definition specifies the HTTP verb (getin the above example withget 'preview'). In addition toget, you canusepatch,put,post, ordelete.

If you don't have multiplemember routes, you can alsopass:on to a route, eliminating the block:

resources:photosdoget"preview",on: :memberend

You can also leave out the:on option, this will create the same member route except that the resource id value will be available inparams[:photo_id] instead ofparams[:id]. Route helpers will also be renamed frompreview_photo_url andpreview_photo_path tophoto_preview_url andphoto_preview_path.

2.10.2. Adding Collection Routes

To add a route to the collection, use acollection block:

resources:photosdocollectiondoget"search"endend

This will enable Rails to recognize paths such as/photos/search with GET, and route to thesearch action ofPhotosController. It will also create thesearch_photos_url andsearch_photos_path route helpers.

Just as with member routes, you can pass:on to a route:

resources:photosdoget"search",on: :collectionend

2.10.3. Adding Routes for Additional New Actions

To add an alternate new action using the:on shortcut:

resources:commentsdoget"preview",on: :newend

This will enable Rails to recognize paths such as/comments/new/preview with GET, and route to thepreview action ofCommentsController. It will also create thepreview_new_comment_url andpreview_new_comment_path route helpers.

It is possible to customize the default routes and helpers generated byresources, seecustomizing resourceful routes section for more.

3. Non-Resourceful Routes

In addition to resourceful routing withresources, Rails has powerful support for routing arbitrary URLs to actions. You don't get groups of routes automatically generated by resourceful routing. Instead, you set up each route separately within your application.

While you should usually use resourceful routing, there are places where non-resourceful routing is more appropriate. There's no need to try to force every last piece of your application into a resourceful framework if that's not a good fit.

One example use case for non-resourceful routing is mapping existing legacy URLs to new Rails actions.

3.1. Bound Parameters

When you set up a regular route, you supply a series of symbols that Rails maps to parts of an incoming HTTP request. For example, consider this route:

get"photos(/:id)",to:"photos#display"

If an incomingGET request of/photos/1 is processed by this route, then the result will be to invoke thedisplay action of thePhotosController, and to make the final parameter"1" available asparams[:id]. This route will also route the incoming request of/photos toPhotosController#display, since:id is an optional parameter, denoted by parentheses in the above example.

3.2. Dynamic Segments

You can set up as many dynamic segments within a regular route as you like. Any segment will be available to the action as part ofparams. If you set up this route:

get"photos/:id/:user_id",to:"photos#show"

This route will respond to paths such as/photos/1/2. Theparams hash will be { controller: 'photos', action: 'show', id: '1', user_id: '2' }.

3.3. Static Segments

You can specify static segments when creating a route by not prepending a colon to a segment:

get"photos/:id/with_user/:user_id",to:"photos#show"

This route would respond to paths such as/photos/1/with_user/2. In this case,params would be{ controller: 'photos', action: 'show', id: '1', user_id: '2' }.

3.4. The Query String

Theparams will also include any parameters from the query string. For example, with this route:

get"photos/:id",to:"photos#show"

An incomingGET request for/photos/1?user_id=2 will be dispatched to theshow action of thePhotosController class as usual and theparams hash will be{ controller: 'photos', action: 'show', id: '1', user_id: '2' }.

3.5. Defining Default Parameters

You can define 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:

get"photos/:id",to:"photos#show",defaults:{format:"jpg"}

Rails would matchphotos/12 to theshow action ofPhotosController, and setparams[:format] to"jpg".

You can also use adefaults block to define the defaults for multiple items:

defaultsformat: :jsondoresources:photosresources:articlesend

3.6. Naming Routes

You can specify a name that will be used by the_path and_url helpers for any route using the:as option:

get"exit",to:"sessions#destroy",as: :logout

This will createlogout_path andlogout_url as the route helpers in your application. Callinglogout_path will return/exit.

You can also useas to override routing helper names defined byresources by placing a custom route definitionbefore the resource is defined, like this:

get":username",to:"users#show",as: :userresources:users

This will define auser_path helper that will match/:username (e.g./jane). Inside theshow action ofUsersController,params[:username] will contain the username for the user.

3.7. HTTP Verb Constraints

In general, you should use theget,post,put,patch, anddelete methods to constrain a route to a particular verb. There is amatch method that you could use with the:via option to match multiple verbs at once:

match"photos",to:"photos#show",via:[:get,:post]

The above route matches GET and POST requests to theshow action of thePhotosController.

You can match all verbs to a particular route usingvia: :all:

match"photos",to:"photos#show",via: :all

3.8. Segment Constraints

You can use the:constraints option to enforce a format for a dynamic segment:

get"photos/:id",to:"photos#show",constraints:{id:/[A-Z]\d{5}/}

The above route definition requiresid to be 5 alphanumeric characters long. Therefore, this route would match paths such as/photos/A12345, but not/photos/893. You can more succinctly express the same route this way:

get"photos/:id",to:"photos#show",id:/[A-Z]\d{5}/

The:constraints option takes regular expressions (as well as any object that responds tomatches? method) with the restriction that regexp anchors can't be used. For example, the following route will not work:

get"/:id",to:"articles#show",constraints:{id:/^\d/}

However, note that you don't need to use anchors because all routes are anchored at the start and the end.

For example:

get"/:id",to:"articles#show",constraints:{id:/\d.+/}get"/:username",to:"users#show"

The above routes would allow sharing the root namespace and:

• route paths that always begin with a number, like/1-hello-world, toarticles withid value.
• route paths that never begin with a number, like/david, tousers withusername value.

3.9. Request-Based Constraints

You can also constrain a route based on any method on theRequest object that returns aString.

You specify a request-based constraint the same way that you specify a segment constraint. For example:

get"photos",to:"photos#index",constraints:{subdomain:"admin"}

Will match an incoming request with a path toadmin subdomain.

You can also specify constraints by using aconstraints block:

constraintssubdomain:"admin"doresources:photosend

Will match something likehttps://admin.example.com/photos.

Request constraints work by calling a method on theRequest object with the same name as the hash key and then comparing the return value with the hash value. For example:constraints: { subdomain: 'api' } will match anapi subdomain as expected. However, using a symbolconstraints: { subdomain: :api } will not, becauserequest.subdomain returns'api' as a String.

There is an exception for theformat constraint, while it's a method on the Request object, it's also an implicit optional parameter on every path. Segment constraints take precedence and theformat constraint is only applied when enforced through a hash. For example,get 'foo', constraints: { format: 'json' } will matchGET /foo because the format is optional by default.

3.10. Advanced Constraints

If you have a more advanced constraint, you can provide an object that responds tomatches? that Rails should use. Let's say you wanted to route all users on a restricted list to theRestrictedListController. You could do:

classRestrictedListConstraintdefinitialize@ips=RestrictedList.retrieve_ipsenddefmatches?(request)@ips.include?(request.remote_ip)endendRails.application.routes.drawdoget"*path",to:"restricted_list#index",constraints:RestrictedListConstraint.newend

You can also specify constraints as a lambda:

Rails.application.routes.drawdoget"*path",to:"restricted_list#index",constraints:lambda{|request|RestrictedList.retrieve_ips.include?(request.remote_ip)}end

Both thematches? method and the lambda gets therequest object as an argument.

3.10.1. Constraints in a Block Form

You can specify constraints in a block form. This is useful for when you need to apply the same rule to several routes. For example:

classRestrictedListConstraint# ...Same as the example aboveendRails.application.routes.drawdoconstraints(RestrictedListConstraint.new)doget"*path",to:"restricted_list#index"get"*other-path",to:"other_restricted_list#index"endend

You can also use alambda:

Rails.application.routes.drawdoconstraints(lambda{|request|RestrictedList.retrieve_ips.include?(request.remote_ip)})doget"*path",to:"restricted_list#index"get"*other-path",to:"other_restricted_list#index"endend

3.11. Wildcard Segments

A route definition can have a wildcard segment, which is a segment prefixed with a star, such as*other:

get"photos/*other",to:"photos#unknown"

Wildcard segments allow for something called "route globbing", which is a way to specify that a particular parameter (*other above) be matched to the remaining part of a route.

So the above route would matchphotos/12 or/photos/long/path/to/12, settingparams[:other] to"12" or"long/path/to/12".

Wildcard segments can occur anywhere in a route. For example:

get"books/*section/:title",to:"books#show"

would matchbooks/some/section/last-words-a-memoir withparams[:section] equals'some/section', andparams[:title] equals'last-words-a-memoir'.

Technically, a route can have even more than one wildcard segment. The matcher assigns segments to parameters in the order they occur. For example:

get"*a/foo/*b",to:"test#index"

would matchzoo/woo/foo/bar/baz withparams[:a] equals'zoo/woo', andparams[:b] equals'bar/baz'.

3.12. Format Segments

Given this route definition:

get"*pages",to:"pages#show"

By requesting'/foo/bar.json', yourparams[:pages] will be equal to'foo/bar' with the request format of JSON inparams[:format].

The default behavior withformat is that if included Rails automatically captures it from the URL and includes it in params[:format], butformat is not required in a URL.

If you want to match URLs without an explicit format and ignore URLs that include a format extension, you could supplyformat: false like this:

get"*pages",to:"pages#show",format:false

If you want to make the format segment mandatory, so it cannot be omitted, you can supplyformat: true like this:

get"*pages",to:"pages#show",format:true

3.13. Redirection

You can redirect any path to any other path by using theredirect helper in your router:

get"/stories",to:redirect("/articles")

You can also reuse dynamic segments from the match in the path to redirect to:

get"/stories/:name",to:redirect("/articles/%{name}")

You can also provide a block toredirect, which receives the symbolized path parameters and the request object:

get"/stories/:name",to:redirect{|path_params,req|"/articles/#{path_params[:name].pluralize}"}get"/stories",to:redirect{|path_params,req|"/articles/#{req.subdomain}"}

Please note that default redirection is a 301 "Moved Permanently" redirect. Keep in mind that some web browsers or proxy servers will cache this type of redirect, making the old page inaccessible. You can use the:status option to change the response status:

get"/stories/:name",to:redirect("/articles/%{name}",status:302)

In all of these cases, if you don't provide the host (http://www.example.com), Rails will take those details from the current request.

3.14. Routing to Rack Applications

Instead of specifying:to as a String like'articles#index', which corresponds to theindex method in theArticlesController class, you can specify anyRack application as the endpoint for a matcher:

match"/application.js",to:MyRackApp,via: :all

As long asMyRackApp responds tocall and returns a[status, headers, body], the router won't know the difference between the Rack application and a controller action. This is an appropriate use ofvia: :all, as you will want to allow your Rack application to handle all verbs.

If you specify a Rack application as the endpoint for a matcher, remember thatthe route will be unchanged in the receiving application. With the followingroute your Rack application should expect the route to be/admin:

match"/admin",to:AdminApp,via: :all

If you would prefer to have your Rack application receive requests at the rootpath instead, usemount:

mountAdminApp,at:"/admin"

3.15. Usingroot

You can specify what Rails should route'/' to with theroot method:

rootto:"pages#main"root"pages#main"# shortcut for the above

You typically put theroot route at the top of the file so that it can be matched first.

You can also use root inside namespaces and scopes as well:

rootto:"home#index"namespace:admindorootto:"admin#index"end

The above will match/admin to theindex action for theAdminController and match/ toindex action of theHomeController.

3.16. Unicode Character Routes

You can specify unicode character routes directly. For example:

get"こんにちは",to:"welcome#index"

3.17. Direct Routes

You can create custom URL helpers by callingdirect. For example:

direct:homepagedo"https://rubyonrails.org"end# >> homepage_url# => "https://rubyonrails.org"

The return value of the block must be a valid argument for theurl_for method. So, you can pass a valid string URL, Hash, Array, an Active Model instance, or an Active Model class.

direct:commentabledo|model|[model,anchor:model.dom_id]end

direct:maindo{controller:"pages",action:"index",subdomain:"www"}end# >> main_url# => "http://www.example.com/pages"

3.18. Usingresolve

Theresolve method allows customizing polymorphic mapping of models. For example:

resource:basketresolve("Basket"){[:basket]}

<%=form_withmodel:@basketdo|form|%><!-- basket form --><%end%>

This will generate the singular URL/basket instead of the usual/baskets/:id.

4. Customizing Resourceful Routes

While the default routes and helpers generated byresources will usually serve you well, you may need to customize them in some way. Rails allows for several different ways to customize the resourceful routes and helpers. This section will detail the available options.

4.1. Specifying a Controller to Use

The:controller option lets you explicitly specify a controller to use for the resource. For example:

resources:photos,controller:"images"

will recognize incoming paths beginning with/photos but route to theImages controller:

For namespaced controllers you can use the directory notation. For example:

resources:user_permissions,controller:"admin/user_permissions"

This will route to theAdmin::UserPermissionsController instance.

4.2. Specifying Constraints onid

You can use the:constraints option to specify a required format on the implicitid. For example:

resources:photos,constraints:{id:/[A-Z][A-Z][0-9]+/}

This declaration constrains the:id parameter to match the given regular expression. The router would no longer match/photos/1 to this route. Instead,/photos/RR27 would match.

You can specify a single constraint to apply to a number of routes by using the block form:

constraints(id:/[A-Z][A-Z][0-9]+/)doresources:photosresources:accountsend

4.3. Overriding the Named Route Helpers

The:as option lets you override the default naming for the route helpers. For example:

resources:photos,as:"images"

This will match/photos and route the requests toPhotosController as usual,but use the value of the:as option to name the helpersimages_path etc., as shown:

4.4. Renaming thenew andedit Path Names

The:path_names option lets you override the defaultnew andedit segment in paths. For example:

resources:photos,path_names:{new:"make",edit:"change"}

This would allow paths such as/photos/make and/photos/1/change instead of/photos/new and/photos/1/edit.

It is also possible to change this option uniformly for all of your routes by using ascope block:

scopepath_names:{new:"make"}do# rest of your routesend

4.5. Prefixing the Named Route Helpers with:as

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. For example:

scope"admin"doresources:photos,as:"admin_photos"endresources:photos

This changes the route helpers for/admin/photos fromphotos_path,new_photos_path, etc. toadmin_photos_path,new_admin_photo_path, etc.Without the addition ofas: 'admin_photos' on the scopedresources :photos,the non-scopedresources :photos will not have any route helpers.

To prefix a group of route helpers, use:as withscope:

scope"admin",as:"admin"doresources:photos,:accountsendresources:photos,:accounts

Just as before, this changes the/admin scoped resource helpers toadmin_photos_path andadmin_accounts_path, and allows the non-scopedresources to usephotos_path andaccounts_path.

4.6. Using:as in Nested Resources

The:as option can override routing helper names for resources in nested routes as well. For example:

resources:magazinesdoresources:ads,as:"periodical_ads"end

This will create routing helpers such asmagazine_periodical_ads_url andedit_magazine_periodical_ad_path instead of the defaultmagazine_ads_url andedit_magazine_ad_path.

4.7. Parametric Scopes

You can prefix routes with a named parameter:

scope":account_id",as:"account",constraints:{account_id:/\d+/}doresources:articlesend

This will provide you with paths such as/1/articles/9 and will allow you to reference theaccount_id part of the path asparams[:account_id] in controllers, helpers, and views.

It will also generate path and URL helpers prefixed withaccount_, into which you can pass your objects as expected:

account_article_path(@account,@article)# => /1/article/9url_for([@account,@article])# => /1/article/9form_with(model:[@account,@article])# => <form action="/1/article/9" ...>

The:as option is also not mandatory, but without it, Rails will raise an error when evaluatingurl_for([@account, @article]) or other helpers that rely onurl_for, such asform_with.

4.8. Restricting the Routes Created

By default, usingresources creates routes for the seven default actions (index,show,new,create,edit,update, anddestroy). You can use the:only and:except options to limit which routes are created.

The:only option tells Rails to create only the specified routes:

resources:photos,only:[:index,:show]

Now, aGET request to/photos or/photos/:id would succeed, but aPOST request to/photos will fail to match.

The:except option specifies a route or list of routes that Rails shouldnot create:

resources:photos,except: :destroy

In this case, Rails will create all of the normal routes except the route fordestroy (aDELETE request to/photos/:id).

4.9. Translated Paths

Usingscope, we can alter path names generated byresources:

scope(path_names:{new:"neu",edit:"bearbeiten"})doresources:categories,path:"kategorien"end

Rails now creates routes to theCategoriesController.

4.10. Specifying the Singular Form of a Resource

If you need to override the singular form of a resource, you can add a rule to Active Support Inflector viainflections:

ActiveSupport::Inflector.inflectionsdo|inflect|inflect.irregular"tooth","teeth"end

4.11. Renaming Default Route Parameterid

It is possible to rename the default parameter nameid with the:param option. For example:

resources:videos,param: :identifier

Will now useparams[:identifier] instead ofparams[:id].

    videos GET  /videos(.:format)                  videos#index           POST /videos(.:format)                  videos#create new_video GET  /videos/new(.:format)              videos#newedit_video GET  /videos/:identifier/edit(.:format) videos#edit

Video.find_by(id:params[:identifier])# Instead ofVideo.find_by(id:params[:id])

You can overrideActiveRecord::Base#to_param of the associated model to construct a URL:

classVideo<ApplicationRecorddefto_paramidentifierendend

irb>video=Video.find_by(identifier:"Roman-Holiday")irb>edit_video_path(video)=>"/videos/Roman-Holiday/edit"

5. Inspecting Routes

Rails offers a few different ways of inspecting and testing your routes.

5.1. Listing Existing Routes

To get a complete list of routes available in an application, visithttp://localhost:3000/rails/info/routes in thedevelopment environment. You can also execute thebin/rails routes command in your terminal to get the same output.

Both methods will list all of your routes, in the same order that they appear inconfig/routes.rb. For each route, you'll see:

• The route name (if any)
• The HTTP verb used (if the route doesn't respond to all verbs)
• The URL pattern to match
• The routing parameters for the route

For example, here's a small section of thebin/rails routes output for a RESTful route:

    users GET    /users(.:format)          users#index          POST   /users(.:format)          users#create new_user GET    /users/new(.:format)      users#newedit_user GET    /users/:id/edit(.:format) users#edit

The route name (new_user above, for example) can be considered the base for deriving route helpers. To get the name of a route helper, add the suffix_path or_url to the route name (new_user_path, for example).

You can also use the--expanded option to turn on the expanded table formatting mode.

$bin/railsroutes--expanded--[ Route 1 ]----------------------------------------------------Prefix            | usersVerb              | GETURI               | /users(.:format)Controller#Action |users#index--[ Route 2 ]----------------------------------------------------Prefix            |Verb              | POSTURI               | /users(.:format)Controller#Action |users#create--[ Route 3 ]----------------------------------------------------Prefix            | new_userVerb              | GETURI               | /users/new(.:format)Controller#Action |users#new--[ Route 4 ]----------------------------------------------------Prefix            | edit_userVerb              | GETURI               | /users/:id/edit(.:format)Controller#Action |users#edit

5.2. Searching Routes

You can search through your routes with the grep option:-g. This outputs any routes that partially match the URL helper method name, the HTTP verb, or the URL path.

$bin/railsroutes-g new_comment$bin/railsroutes-g POST$bin/railsroutes-g admin

If you only want to see the routes that map to a specific controller, there's the controller option:-c.

$bin/railsroutes-cusers$bin/railsroutes-c admin/users$bin/railsroutes-c Comments$bin/railsroutes-c Articles::CommentsController

5.3. Listing Unused Routes

You can scan your application for unused routes with the--unused option. An "unused" route in Rails is a route that is defined in the config/routes.rb file but is not referenced by any controller action or view in your application. For example:

$bin/railsroutes--unusedFound 8 unused routes:     Prefix Verb   URI Pattern                Controller#Action     people GET    /people(.:format)          people#index            POST   /people(.:format)          people#create new_person GET    /people/new(.:format)      people#newedit_person GET    /people/:id/edit(.:format) people#edit     person GET    /people/:id(.:format)      people#show            PATCH  /people/:id(.:format)      people#update            PUT    /people/:id(.:format)      people#update            DELETE /people/:id(.:format)      people#destroy

5.4. Routes in Rails Console

You can access route helpers usingRails.application.routes.url_helpers within theRails Console. They are also available via theapp object. For example:

irb>Rails.application.routes.url_helpers.users_path=>"/users"irb>user=User.first=>#<User:0x00007fc1eab81628irb>app.edit_user_path(user)=>"/users/1/edit"

6. Testing Routes

Rails offers three built-in assertions designed to make testing routes simpler:

• assert_generates
• assert_recognizes
• assert_routing

6.1. Theassert_generates Assertion

assert_generates asserts that a particular set of options generate a particular path and can be used with default routes or custom routes. For example:

assert_generates"/photos/1",{controller:"photos",action:"show",id:"1"}assert_generates"/about",controller:"pages",action:"about"

6.2. Theassert_recognizes Assertion

assert_recognizes is the inverse ofassert_generates. It asserts that a given path is recognized and routes it to a particular spot in your application. For example:

assert_recognizes({controller:"photos",action:"show",id:"1"},"/photos/1")

You can supply a:method argument to specify the HTTP verb:

assert_recognizes({controller:"photos",action:"create"},{path:"photos",method: :post})

6.3. Theassert_routing Assertion

Theassert_routing assertion checks the route both ways. It combines the functionality of bothassert_generates andassert_recognizes. It tests that the path generates the options, and that the options generate the path:

assert_routing({path:"photos",method: :post},{controller:"photos",action:"create"})

7. Breaking Up a Large Route File Withdraw

In a large application with thousands of routes, a singleconfig/routes.rb file can become cumbersome and hard to read. Rails offers a way to break up a singleroutes.rb file into multiple small ones using thedraw macro.

For example, you could add anadmin.rb file that contains all the routes related to the admin area, anotherapi.rb file for API related resources, etc.

# config/routes.rbRails.application.routes.drawdoget"foo",to:"foo#bar"draw(:admin)# Will load another route file located in `config/routes/admin.rb`end

# config/routes/admin.rbnamespace:admindoresources:commentsend

Callingdraw(:admin) inside theRails.application.routes.draw block itselfwill try to load a route file that has the same name as the argument given(admin.rb in this example). The file needs to be located inside theconfig/routes directory or any sub-directory (i.e.config/routes/admin.rb orconfig/routes/external/admin.rb).