Overview

Here is a simple guideline to create a simple API with RoR5. In this post, I'll create a simple blog like application that users can read, create, update and delete posts on.
The complete code is available here

Table of contents

1. Create the application
2. Create the controller and model for Post
3. Set up Routes with namespaces
4. Set up the Post controller
5. Test the api using postman

Overview

Here is a simple guideline to create a simple API with RoR5. In this post, I'll create a simple blog like application that users can read, create, update and delete posts on.

Create the application

You can make an API-only RoR application by just adding --api at the end of rails new command.

$ rails new blog --api 

Create the controller and model for Post

You can generate the Post Controller and Post Model by running commands below.

$ rails g model post title:string $ rails g controller posts $ rake db:migrate 

Set up Routes with namespaces

Namespaces enable you to easily control the version of your API.

Rails.application.routes.draw do namespace 'api' do namespace 'v1' do resources :posts end end end 

The code above creates routes like this. (You can check the routes of your application with rake routes command.)

$ rake routes api_v1_posts GET /api/v1/posts(.:format) api/v1/posts#index  POST /api/v1/posts(.:format) api/v1/posts#create  api_v1_post GET /api/v1/posts/:id(.:format) api/v1/posts#show  PATCH /api/v1/posts/:id(.:format) api/v1/posts#update  PUT /api/v1/posts/:id(.:format) api/v1/posts#update  DELETE /api/v1/posts/:id(.:format) api/v1/posts#destroy 

Set up the Post controller.

Create the api and v1 directories under your controllers directory. Your controllers directory should look like this.

---- controllers --- api -- v1 - posts_controller.rb 

Create methods for getting, creating, updating and deleting posts like the code below.

module Api module V1 class PostsController < ApplicationController def index posts = Post.order(created_at: :desc) render json: { status: 'SUCCESS', message: 'loaded posts', data: posts } end def show post = Post.find(params[:id]) render json: { status: 'SUCCESS', message: 'loaded the post', data: post } end def create post = Post.new(post_params) if post.save render json: { status: 'SUCCESS', message: 'loaded the post', data: post } else render json: { status: 'ERROR', message: 'post not saved', data: post.errors } end end def destroy post = Post.find(params[:id]) post.destroy render json: { status: 'SUCCESS', message: 'deleted the post', data: post } end def update post = Post.find(params[:id]) if post.update(post_params) render json: { status: 'SUCCESS', message: 'updated the post', data: post } else render json: { status: 'SUCCESS', message: 'loaded the post', data: post } end end private def post_params params.require(:post).permit(:title) end end end end 

Test the api using postman

Let's create some data we can play with on rails console.

$ rails c 2.4.4 :001 > Post.create(title:'title1') 2.4.4 :001 > Post.create(title:'title2') 

Next, Run the api!

$ rails s 

Open postman and test the following requests.

Get(http://localhost:3000/api/v1/posts)

You can retrieve 2 sets of data you have created on the console.

GET(http://localhost:3000/api/v1/posts/:id)

You can retrieve one specific data that has id = 1.

POST (http://localhost:3000/api/v1/posts)

Let's create data!
When you create data, you have to send a POST request.

So change the selected option in the box on the right from GET to POST and pass json data in the body.

PUT(http://localhost:3000/api/v1/posts/:id)

Let's Update data!
Change the selected option to PUT and pass json data.

DELETE(http://localhost:3000/api/v1/posts/:id)

Lastly, let's try to delete data.
Change the selected option to DELETE and pass json data.

I've usded postman in this post, but you can of course use curl command to do the same.