Every time I create a new Rails API with a PostgreSQL database, I find myself googling “create a new Rails API with a PostgreSQL database”. So I’m leaving these notes here for myself, and anyone else who finds this helpful.

For the purpose of this tutorial, let’s imagine we’re creating a super awesome app, and we’re going to call it Super Awesome App.

Installation of Ruby and Rails

The first step to building a RESTful CRUD API with Ruby on Rails is to verify that both Ruby and Rails are installed. (macOS Steps)

Open the terminal and run the following command:

ruby -v

This command verifies the version of Ruby installed. If Ruby is not installed, run the following command:

rvm install 2.7.4 --default
# replace 2.7.4 with the desired Ruby version

To install Rails, run the following command:

gem install bundler
gem install rails

Installation of PostgreSQL

Download the latest version of Postgres from Postgres.app or install using brew:

brew install postgresql
brew services start postgresql

Create a Rails Application

Open the terminal or command prompt, navigate to the desired directory, and run the following command:

rails new redwhite_project --api --minimal --database=postgresql

This command sets the application to be an API with minimal dependencies and sets the database to PostgreSQL.

Generating a Resource

The next step is to create a migration and model for the API. This can be accomplished by using a Rails generator.

Open the terminal or command prompt and run the following command:

rails g resource Minister first_name last_name genre

# This is also be written as:
# rails g resource Minister first_name:string last_name:string genre:string

This command generates a new model, controller, and migration file for the Minister resource.

Optional: Create Seed Data

Open the seeds file located at db/seeds.rb and input the following:

Minister.create!(first_name: 'xam', last_name: 'Txhomas', genre: 'rock')
Minister.create!(first_name: 'xarah', last_name: 'Jxones', genre: 'pop')
Minister.create!(first_name: 'xoe', last_name: 'Sxmith', genre: 'country')
Minister.create!(first_name: 'xen', last_name: 'Axdams', genre: 'folk')

Perform Migration

Open the terminal or command prompt and run the following command:

rails db:create db:migrate 
# If using seed data, run: 
# rails db:create db:migrate db:seed

when finding error just do 2 this optional

rake db:create:all

rake db:migrate

Define the Config Routes

Navigate to config/routes.rb and define the routes using one of the following methods:

Rails.application.routes.draw do
  # Option 1 - Allow all controller actions
  resources : minister
  # Option 2 - Allow specific controller actions
  resources :minister, only: [:index, :create, :destroy]
  # Option 3 - Define specific controller action
  get '/minister', to: 'minister#index'
end

Define Controller Actions

Suggested Active Record Rescues

The rescue_from method is an important feature in Rails that enables centralized error handling, thereby preventing duplication of error handling logic across multiple controller actions. For example, the ActiveRecord::RecordNotFound exception occurs when a record is not found in the database and is handled by rendering a 404 Record Not Found response to the user. On the other hand, the ActiveRecord::RecordInvalid exception is raised when a record fails to save to the database due to validation errors and is handled by rendering a 422 Unprocessable Entity response along with the validation errors.

class Minister < ApplicationController
  rescue_from ActiveRecord::RecordNotFound, with: :render_not_found_response
  rescue_from ActiveRecord::RecordInvalid, with: :render_unprocessable_entity_response

  private

  def render_not_found_response
    render json: { error: "Minister Not Found" }, status: :not_found
  end

  def render_unprocessable_entity_response(invalid)
    render json: { errors: invalid.record.errors.full_messages }, status: :unprocessable_entity
  end
end

**Index Action: GET /**minister

This route is used to retrieve a collection of resources. Typically returns a list of all the resources in the database.

def index
  render json: Minister.all
end

Show Action: GET /minister/:id

This route is used to retrieve a single resource by its unique identifier or primary key. Typically returns a single resource.

def show
  render json: Minister.find(params[:id])
end

**Create Action: POST /**minister

This route is used to create a new resource. Typically returns the newly created resource.

def create
  minister = Minister.create!(minister_params)
  render json: minister, status: :created
end

private

def minister_params
  params.permit(:first_name, :last_name, :genre)
end

Update Action: PATCH or PUT /minister/:id

This route is used to update an existing resource by its unique identifier or primary key. Typically returns the updated resource.

def update
  minister = Minister.find(params[:id])
  minister.update!(minister_params)
  render json: minister
end

Destroy Action: DELETE /minister/:id

This route is used to delete a resource by its unique identifier or primary key. Typically returns a response with a status code of 204 (No Content) to indicate that the resource has been deleted.

def destroy
  Minister.find(params[:id]).destroy
  head :no_content
end

Closing

Thank-you for reading this guide to building a RESTful CRUD API with Ruby on Rails and PostgreSQL.

References;

https://github.com/rokhimin/ruby-CRUD

https://medium.com/@hanpersonality/basic-crud-operations-of-rdbms-with-postgresql-d613c6c4d00c

https://github.com/nejdetkadir/simple-rails-crud

https://dev.to/justahmed99/crud-rest-api-with-nodejs-expressjs-and-postgresql-57b2

https://blog.stackademic.com/building-a-restful-api-with-rails-and-testing-crud-using-postman-e803010b4774

https://medium.com/@ethanryan/creating-a-new-rails-api-with-a-postgresql-database-488ffce649d9

https://github.com/JamesHuangUC/Ruby-on-Rails-CRUD

https://dev.to/nemwelboniface/api-with-rails-7-ngh

https://dev.to/katebennert/building-a-restful-api-with-ruby-on-rails-and-getting-some-rest-yourself--5fl4

https://startup-house.com/blog/creating-a-project-with-ruby-on-rails

https://www.protonshub.com/blogs/power-up-your-development-with-ruby-on-rails

https://github.com/bensheldon/good_job

https://www.protonshub.com/blogs/power-up-your-development-with-ruby-on-rails

https://www.monterail.com/blog/how-to-build-restful-apis-with-ruby-on-rails