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 Routing::Mapper::Resources#resources, Routing::Mapper::Scoping#namespace, and Routing::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 `root` 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 “http://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.

Constants

HTTP_METHODS = [:get, :head, :post, :patch, :put, :delete, :options]

SEPARATORS = %w( / . ? )

Attributes

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