Module: ActionDispatch::Routing

The routing module provides URL rewriting in native Ruby. It’s a way to redirect incoming requests to controllers and actions. This replaces mod_rewrite rules. Best of all, Rails’ Routing works with any web server. Routes are defined in config/routes.rb.

Think of creating routes as drawing a map for your requests. The map tells them where to go based on some predefined pattern:

Rails.application.routes.draw do
  Pattern 1 tells some request to go to one place
  Pattern 2 tell them to go to another
  #...
end

The following symbols are special:

:controller maps to your controller name
:action     maps to an action with your controllers

Other names simply map to a parameter as in the case of :id.

Resources

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:

resources :photos

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.

resource :profile

It’s common to have resources that are logically children of other resources:

resources :magazines do
  resources :ads
end

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:

namespace "admin" do
  resources :posts, :comments
end

Alternatively, you can add prefixes to your path without using a separate directory by using scope. scope takes additional options which apply to all enclosed routes.

scope path: "/cpanel", as: 'admin' do
  resources :posts, :comments
end

For more, see Mapper::Resources#resources, Mapper::Scoping#namespace, and Mapper::Scoping#scope.

Non-resourceful routes

For routes that don’t fit the resources mold, you can use the HTTP helper methods get, post, patch, put and delete.

get 'post/:id', to: 'posts#show'
post 'post/:id', to: 'posts#create_comment'

Now, if you POST to /posts/:id, it will route to the create_comment action. A GET on the same URL will route to the show action.

If your route needs to respond to more than one HTTP method (or all methods) then using the :via option on match is preferable.

match 'post/:id', to: 'posts#show', via: [:get, :post]

Named routes

Routes can be named by passing an :as option, allowing for easy reference within your source as name_of_route_url for the full URL and name_of_route_path for the URI path.

Example:

# In config/routes.rb
get '/login', to: 'accounts#login', as: 'login'

# With render, redirect_to, tests, etc.
redirect_to login_url

Arguments can be passed as well.

redirect_to show_item_path(id: 25)

Use :: as a shorthand to name a route for the root path “/”.

# In config/routes.rb
root to: 'blogs#index'

# would recognize http://www.example.com/ as
params = { controller: 'blogs', action: 'index' }

# and provide these named routes
root_url   # => 'http://www.example.com/'
root_path  # => '/'

Note: when using controller, the route is simply named after the method you call on the block parameter rather than map.

# In config/routes.rb
controller :blog do
  get 'blog/show'    => :list
  get 'blog/delete'  => :delete
  get 'blog/edit'    => :edit
end

# provides named routes for show, delete, and edit
link_to @article.title, blog_show_path(id: @article.id)

Pretty URLs

Routes can generate pretty URLs. For example:

get '/articles/:year/:month/:day', to: 'articles#find_by_id', constraints: {
  year:       /\d{4}/,
  month:      /\d{1,2}/,
  day:        /\d{1,2}/
}

Using the route above, the URL “localhost:3000/articles/2005/11/06” maps to

params = {year: '2005', month: '11', day: '06'}

Regular Expressions and parameters

You can specify a regular expression to define a format for a parameter.

controller 'geocode' do
  get 'geocode/:postalcode', to: :show, constraints: {
    postalcode: /\d{5}(-\d{4})?/
  }
end

Constraints can include the ‘ignorecase’ and ‘extended syntax’ regular expression modifiers:

controller 'geocode' do
  get 'geocode/:postalcode', to: :show, constraints: {
    postalcode: /hx\d\d\s\d[a-z]{2}/i
  }
end

controller 'geocode' do
  get 'geocode/:postalcode', to: :show, constraints: {
    postalcode: /# Postalcode format
       \d{5} #Prefix
       (-\d{4})? #Suffix
       /x
  }
end

Using the multiline modifier will raise an ArgumentError. Encoding regular expression modifiers are silently ignored. The match will always use the default encoding or ASCII.

External redirects

You can redirect any path to another path using the redirect helper in your router:

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

Unicode character routes

You can specify unicode character routes in your router:

get "こんにちは", to: "welcome#index"

Routing to Rack Applications

Instead of a ::String, like posts#index, which corresponds to the index action in the PostsController, you can specify any ::Rack application as the endpoint for a matcher:

get "/application.js", to: Sprockets

Reloading routes

You can reload routes if you feel you must:

Rails.application.reload_routes!

This will clear all named routes and reload config/routes.rb if the file has been modified from last load. To absolutely force reloading, use reload!.

Testing Routes

The two main methods for testing your routes:

assert_routing

def test_movie_route_properly_splits
  opts = {controller: "plugin", action: "checkout", id: "2"}
  assert_routing "plugin/checkout/2", opts
end

assert_routing lets you test whether or not the route properly resolves into options.

assert_recognizes

def test_route_has_options
  opts = {controller: "plugin", action: "show", id: "12"}
  assert_recognizes opts, "/plugins/show/12"
end

Note the subtle difference between the two: assert_routing tests that a URL fits options while assert_recognizes tests that a URL breaks into parameters properly.

In tests you can simply pass the URL or named route to get or post.

def send_to_jail
  get '/jail'
  assert_response :success
end

def goes_to_login
  get login_url
  #...
end

View a list of all your routes

$ bin/rails routes

Target a specific controller with -c, or grep routes using -g. Useful in conjunction with --expanded which displays routes vertically.