Building REST APIs with Ruby on Rails

Why Rails for APIs?

Ruby on Rails provides convention over configuration, making it easy to build RESTful APIs quickly with built-in best practices.

Creating a Rails API

# Create new Rails API
rails new my_api --api

# Generate scaffold
rails generate scaffold User name:string email:string

# Run migrations
rails db:migrate

# Start server
rails server

API Controller

# app/controllers/api/v1/users_controller.rb
class Api::V1::UsersController < ApplicationController
  before_action :set_user, only: [:show, :update, :destroy]

  # GET /api/v1/users
  def index
    @users = User.all
    render json: @users
  end

  # GET /api/v1/users/1
  def show
    render json: @user
  end

  # POST /api/v1/users
  def create
    @user = User.new(user_params)
    
    if @user.save
      render json: @user, status: :created
    else
      render json: @user.errors, status: :unprocessable_entity
    end
  end

  # PATCH/PUT /api/v1/users/1
  def update
    if @user.update(user_params)
      render json: @user
    else
      render json: @user.errors, status: :unprocessable_entity
    end
  end

  # DELETE /api/v1/users/1
  def destroy
    @user.destroy
    head :no_content
  end

  private

  def set_user
    @user = User.find(params[:id])
  end

  def user_params
    params.require(:user).permit(:name, :email)
  end
end

Routes Configuration

# config/routes.rb
Rails.application.routes.draw do
  namespace :api do
    namespace :v1 do
      resources :users
      resources :posts
    end
  end
end

Serializers

# app/serializers/user_serializer.rb
class UserSerializer
  include FastJsonapi::ObjectSerializer
  
  attributes :id, :name, :email, :created_at
  
  has_many :posts
end

# In controller
def index
  @users = User.all
  render json: UserSerializer.new(@users).serializable_hash
end

Authentication with JWT

# app/controllers/api/v1/auth_controller.rb
class Api::V1::AuthController < ApplicationController
  def login
    @user = User.find_by(email: params[:email])
    
    if @user && @user.authenticate(params[:password])
      token = JWT.encode({ user_id: @user.id }, Rails.application.secret_key_base)
      render json: { token: token, user: @user }
    else
      render json: { error: "Invalid credentials" }, status: :unauthorized
    end
  end
end

Best Practices

• Use API versioning
• Use serializers for JSON responses
• Implement pagination
• Use strong parameters
• Handle errors gracefully