Ruby on Rails - Part 2 - CRUD with Rest standards and Pagination

1) Complete the quick start guide: 

https://localboyfrommadurai.blogspot.com/2021/03/ruby-on-rails-quick-start.html

2) Open Gemfile and the following line

gem 'kaminari'

This library helps for pagination

3) Install the gem:

bundle install

4) Modify app/controllers/application_controller.rb

class ApplicationController < ActionController::Base
    protect_from_forgery with: :null_session
end

Adding this will allow the requests such as PUT, POST and DELETE calls without session authentication.

5) Modify config/routes.rb

Rails.application.routes.draw do
  get 'users(/:page_no)' => 'users#list', :defaults => { :page_no => 1 }
  delete 'users/:user_id' => 'users#delete'
  put 'users/:user_id' => 'users#update'
  post 'users' => 'users#create'
end

6) Modify app/controllers/users_controller.rb

class UsersController < ApplicationController
    def update
        params.require(:name)
        user = User.find(params[:user_id])
        if user
            user.update(name: params[:name])
            render json: {}, status: :ok
            return
        end
        render json: {}, status: :not_found
    end

    def create
        params.require(:name)
        user = User.create({:name => params[:name]})
        render json: user, status: :ok
    end

    def list
        @users = User.page(params[:page_no]).per(5)
        render 'users/list'
    end


    def delete
        User.delete(params[:user_id])
        render json: {}, status: :no_content
    end
end

7) Modify app/views/users/list.html.erb

<h1>Users</h1>

<ul>
  <% @users.each do |user| %>
    <li>
      <div><b>ID: </b><%= user.id %> </div>
      <div><b>Name: </b><%= user.name %> </div>
    </li>
  <% end %>
</ul>

Results:

Happy coding :)

Ruby on Rails quick start!

1) Create an application and run it!

rails new blog --skip-bundle
cd blog
bundle config set --local path 'vendor/bundle'
bundle install
rails webpacker:install
rails s

Open http://localhost:3000/




2) Create an API:




Add routes in config/routes.rb    

Rails.application.routes.draw do
  get 'users' => 'users#index'
end

Add a controller at app/controllers/users_controller.rb

class UsersController < ApplicationController
    def index
        render :json => 'Users Page'
    end
end

Open http://localhost:3000/users

3) To render a template:

Create a html file in app/views/users/index.html.erb

<h1>Users Index</h1>

Modify app/controllers/users_controller.rb to render the template

class UsersController < ApplicationController
    def index
        render 'users/index'
    end
end

Open http://localhost:3000/users

4) Connecting to database!

Modify config/database.yml

default: &default
  adapter: mysql2
  encoding: utf8
  database: your_database_name
  pool: 5
  host: 127.0.0.1
  username: root
  password: 
  slave:
    host: 127.0.0.1 

development:
  <<: *default

Add the following line in Gemfile

gem 'mysql2'

Install this gem

bundle install

Add a users model and start the server

rails generate model user
rails s

Add a column in the migration file at db/migrate/xxxxx_create_users.rb

class CreateUsers < ActiveRecord::Migration[6.1]
  def change
    create_table :users do |t|
      t.string :name
      t.timestamps
    end
  end
end

In config/routes.rb add a route to list the users

Rails.application.routes.draw do
  get 'users/list' => 'users#list'
  get 'users' => 'users#index'
end

In app/controllers/users_controller.rb add the code to create and query from database

class UsersController < ApplicationController
    def index
        name = 'User ' + rand(1..10000).to_s
        User.create({:name => name})
        render 'users/index'
    end
    def list
        @users = User.all
        render 'users/list'
    end
end

Create a view to render the users in app/views/users/list.html.erb

<h1>Users</h1>

<ul>
  <% @users.each do |user| %>
    <li>
      <%= user.name %>
    </li>
  <% end %>
</ul>

Run migration and start the server

rails db:migrate
rails s

Open http://localhost:3000/users and refresh the page several times to create new users

Open http://localhost:3000/users/list to view the list of users created

Happy coding!