Routing in Rails

What exactly is routing?

When there's an HTTP request from the user to the application, it should be directed to the right controller. You can picture a router as a receptionist at who connects you to the right person to talk to.

How is routing done in Ruby on Rails?

In Rails, the routes of your application live in config/routes.rb. The Rails router recognises 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. Let's consider an application to book rooms in different Hotels and take a look at how this works.

Types of HTTP request methods

The application receives an HTTP request which carries along with it a method which could be:

GET - Retrieve a resource

POST - Create a resource

PUT - Completely update a resource

PATCH - Partially update a resource

DELETE - Delete a resource

These methods determine which controller action method is called.

Decoding the http request

If the application receives the request, GET /hotels/1. The request is dispatched to the hotels controller's show action with { id: '1' } in params.

get '/hotels/:id', to: 'hotels#show'

Similarly,

get '/hotels', to: 'hotels#index'
get '/hotels/:id', to: 'hotels#show'
get '/hotels/new', to: 'hotels#new'
post '/hotels', to: 'hotels#create'
get '/hotels/:id/edit', to: 'hotels#edit'
put '/hotels/:id', to: 'hotels#update'
delete '/hotels/:id', to: 'hotels#destroy'

TIP: If you ever want to list all the routes of your application you can use rails routes on your terminal and if you want to list routes of a specific resource, you can use rails routes | grep hotel. This will list all the routes of Hotel.

Defining resources

Like how the receptionist holds a record of all the reservations, the application too has its own record in config/routes.rb.

Rails.application.routes.draw do
  resources :hotels
end

By writing resources :hotels we create all seven different routes in your application, all mapping to the Hotels controller like mentioned above.

If your controller has only a few of these actions you can alter the same with the following keywords.

The keyword only includes only the actions mentioned. resources :hotels, only: [:edit]

There's also the keyword except to name the ones you don't want to include.

resources :hotels, except: [:index]

Single and multiple resources

Sometimes we have a single resource ie. we only have to access a single page instead of referencing an id. That's when we use singular term, resource.

resource :hotels

When you have to define multiple resources,

resources :hotels, :rooms which works the same as

resources :hotels,
resources :rooms

Nested Resources

Sometimes we have nested routes, /hotels/:id/rooms which are a result of resources that are logically children of other resources. For example, suppose your application includes these models:

class Hotel < ApplicationRecord
  has_many :rooms
end

class Room < ApplicationRecord
  belongs_to :hotel
end

In which case we will declare our resources this way,

resources :hotels do
  resources :rooms
end

This declaration helps us access the nested URLs such as /hotels/:id/rooms , /hotels/:id/rooms/:id , /hotels/:id/rooms/new etc

Further Study

If you want to dig deeper into routing, you can refer to Rails Routing from the outside in http://guides.rubyonrails.org/routing.html.

Cover Photo by Javier Allegue Barros on Unsplash (https://unsplash.com/photos/C7B-ExXpOIE)