Creating a REST API with Rails

Rails has the ability to create API-only applications. This results in a lighter-weight app that is more conducive to creating SPAs.

First, let’s create an API only version of our blog app.
```
 rails new color_list_api_rails --api
```

Next, we generate the model for authors

bin/rails g scaffold Color title:string uuid:string color:integer rating:integer

Run the migration:
```
 bin/rails db:migrate
```
Let’s seed the database with some colors.

Color.create(title: 'Ocean at noon', color: 0x029eb6, rating: 5, uuid: '0175d1f0-a8c6-41bf-8d02-df5734d829a4')
Color.create(uuid: "83c7ba2f-7392-4d7d-9e23-35adbe186046",title: "Lawn",color:0x2534486, rating:3)
Color.create(uuid: "a11e3995-b0bd-4d58-8c48-5e49ae7f7f23",title: "Bright red",color: 0x16711680,rating:2)
Color.create(uuid: "49fef18c-475c-4ff7-b2de-7adfdbcbaa24",title: "Orange",color:0xca8102,rating: 0)

bin/rails db:seed

Now just launch the server

bin/rails server

and go to the colors route.
A few things to notice:
- There are no new and edit routes: An API doesn’t use forms, so we don’t need a route to display a form.
- There are no views for Color

CORS (Raw)

Generally speaking, conventional browsers implement a same-origin security policy when it comes to AJAX fetches. That is, AJAX fetches to domains different from the page from which they are made are blocked by default.

Cross-origin resource sharing (CORS) is a standard that allows a web browser and server to interact in a way that permits cross-origin AJAX calls from a browser to a server. In order to use our Rails API-only app, we need to enable CORS on it.

We can do this the “raw” way by adding the header manually: Add the following to index in the controller.

response.headers["Access-Control-Allow-Origin"] = "http://localhost:3000"

CORS (package)

To do this, you need to include the following in the Gemfile of your rails app:

gem 'rack-cors', :require => 'rack/cors’ 

Don’t forget to run the bundle install command after updating the Gemfile:

bundle install

Finally, create a new file, config/initializers/cors.rb with the following content:

Rails.application.config.middleware.insert_before 0, Rack::Cors do
  allow do
    origins 'http://localhost:3000'

    resource '*',
      headers: :any,
      methods: [:get, :post, :put, :patch, :delete, :options, :head]
  end
end

Note that this configuration expects your React app to be running on port 3000. If you are using a different port, adjust the line above accordingly. (By default, Rails runs on port 3000 also; so, if you are running both Rails and React locally, you will have to pick a different port for one of them.)