Course Title: Ruby Programming: From Basics to Advanced Techniques

Section Title: Introduction to Ruby on Rails

Topic: Build a basic Ruby on Rails application with simple CRUD functionality. (Lab topic)

Overview

In this lab exercise, we will build a basic Ruby on Rails application with simple CRUD (Create, Read, Update, Delete) functionality. This exercise is designed to give you hands-on experience with Rails and help you understand how to create a fully functional web application.

Prerequisites

Before starting this lab, make sure you have:

1. Installed Ruby and Rails on your system (refer to the Rails installation guide if you haven't already).
2. Set up aRails development environment.
3. Familiarity with the basics of Rails (MVC architecture, routing, etc.).

Step 1: Create a new Rails application

Open a terminal and run the following command to create a new Rails application:

rails new crud_app

This will create a new Rails application called crud_app.

Step 2: Configure the database

In this lab, we will use SQLite as our database. Open the config/database.yml file and make sure it looks like this:

default: &default
  adapter: sqlite3
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  timeout: 5000

development:
  <<: *default
  database: db/development.sqlite3

test:
  <<: *default
  database: db/test.sqlite3

Step 3: Create a model

In Rails, a model represents a database table. Let's create a Book model:

rails generate model Book title:string author:string

This will create a book.rb file in the app/models directory and a books table in the database.

Step 4: Run the migration

To create the books table in the database, run the following command:

rails db:migrate

Step 5: Create a controller

A controller handles HTTP requests and sends responses. Let's create a BooksController:

rails generate controller Books

This will create a books_controller.rb file in the app/controllers directory.

Step 6: Define CRUD actions

In the books_controller.rb file, add the following methods:

class BooksController < ApplicationController
  def index
    @books = Book.all
  end

  def show
    @book = Book.find(params[:id])
  end

  def new
    @book = Book.new
  end

  def create
    @book = Book.new(book_params)

    if @book.save
      redirect_to books_path
    else
      render :new
    end
  end

  def edit
    @book = Book.find(params[:id])
  end

  def update
    @book = Book.find(params[:id])

    if @book.update(book_params)
      redirect_to books_path
    else
      render :edit
    end
  end

  def destroy
    @book = Book.find(params[:id])
    @book.destroy
    redirect_to books_path
  end

  private

  def book_params
    params.require(:book).permit(:title, :author)
  end
end

These methods handle the CRUD operations:

• index: lists all books
• show: shows a single book
• new: creates a new book
• create: saves a new book
• edit: edits an existing book
• update: updates an existing book
• destroy: deletes a book

Step 7: Add routes

In the config/routes.rb file, add the following routes:

Rails.application.routes.draw do
  resources :books
end

This will create the following routes:

• GET /books: lists all books
• GET /books/:id: shows a single book
• GET /books/new: creates a new book
• POST /books: saves a new book
• GET /books/:id/edit: edits an existing book
• PATCH /books/:id: updates an existing book
• DELETE /books/:id: deletes a book

Step 8: Create views

Create the following views:

• index.html.erb: lists all books
• show.html.erb: shows a single book
• new.html.erb: creates a new book
• edit.html.erb: edits an existing book

You can use the following code as a starting point:

<!-- app/views/books/index.html.erb -->

<h1>Books</h1>

<ul>
  <% @books.each do |book| %>
    <li>
      <%= link_to book.title, book_path(book) %>
    </li>
  <% end %>
</ul>

<!-- app/views/books/show.html.erb -->

<h1><%= @book.title %></h1>

<p>Author: <%= @book.author %></p>

<!-- app/views/books/new.html.erb -->

<h1>New Book</h1>

<%= form_for(@book) do |form| %>
  <%= form.label :title %>
  <%= form.text_field :title %>

  <%= form.label :author %>
  <%= form.text_field :author %>

  <%= form.submit %>
<% end %>

<!-- app/views/books/edit.html.erb -->

<h1>Edit Book</h1>

<%= form_for(@book) do |form| %>
  <%= form.label :title %>
  <%= form.text_field :title %>

  <%= form.label :author %>
  <%= form.text_field :author %>

  <%= form.submit %>
<% end %>

Conclusion

In this lab, we created a basic Ruby on Rails application with simple CRUD functionality. We defined a Book model, created a BooksController with CRUD actions, added routes, and created views to display and edit books.

What's next?

In the next topic, we will explore the routing system in Rails and learn how to create custom routes and actions.

Questions or comments?

If you have any questions or comments about this lab, please leave them below.

External resources:

• Rails Guide: Getting Started
• Rails Guide: Active Record
• Rails Guide: ActionController
• Rails Guide: Routing