**Course Title:** Mastering Ruby on Rails: Building Scalable Web Applications **Section Title:** Routing, Controllers, and Views **Topic:** Create a simple web application with routing, controllers, and views that display and manage data.(Lab topic) **Objective:** In this lab, we will create a simple web application using Ruby on Rails that displays and manages data. We will apply the concepts learned in the previous topics, including routing, controllers, and views, to build a fully functional application. **Lab Application:** Bookshelf Manager We will create a Bookshelf Manager application that allows users to create, read, update, and delete books. This application will demonstrate how to handle CRUD (Create, Read, Update, Delete) operations in Rails. **Step 1: Generate the Application** Open your terminal and create a new Rails application using the following command: ```bash rails new bookshelf ``` Navigate to the newly created application directory: ```bash cd bookshelf ``` **Step 2: Define the Model** In Rails, the model represents the data structure of our application. We will create a `Book` model with attributes `title`, `author`, and `published_at`. ```ruby # app/models/book.rb class Book < ApplicationRecord validates :title, presence: true validates :author, presence: true validates :published_at, presence: true end ``` **Step 3: Create the Database Table** To create the database table for our `Book` model, we will run a Rails migration. Open the terminal and execute the following command: ```bash rails generate migration CreateBooks ``` This will create a new migration file in the `db/migrate` directory. Open this file and add the following code: ```ruby # db/migrate/..._create_books.rb class CreateBooks < ActiveRecord::Migration[7.0] def change create_table :books do |t| t.string :title t.string :author t.date :published_at t.timestamps end end end ``` Run the migration to create the database table: ```bash rails db:migrate ``` **Step 4: Define the Routes** We will define routes for our application to handle CRUD operations. Open the `config/routes.rb` file and add the following code: ```ruby # config/routes.rb Rails.application.routes.draw do resources :books end ``` **Step 5: Create the Controller** We will create a `BooksController` to handle requests for our `Book` model. Open the `app/controllers/books_controller.rb` file and add the following code: ```ruby # app/controllers/books_controller.rb class BooksController < ApplicationController def index @books = Book.all end def new @book = Book.new end def create @book = Book.new(book_params) if @book.save redirect_to books_path, notice: 'Book created successfully!' else render :new end end def show @book = Book.find(params[:id]) end def edit @book = Book.find(params[:id]) end def update @book = Book.find(params[:id]) if @book.update(book_params) redirect_to book_path(@book), notice: 'Book updated successfully!' else render :edit end end def destroy @book = Book.find(params[:id]) @book.destroy redirect_to books_path, notice: 'Book deleted successfully!' end private def book_params params.require(:book).permit(:title, :author, :published_at) end end ``` **Step 6: Create the Views** We will create views for each action in our `BooksController`. Open the `app/views/books` directory and create the following files: * `index.html.erb` for displaying a list of books * `new.html.erb` for creating a new book * `edit.html.erb` for editing an existing book * `show.html.erb` for displaying a single book Here is an example of what the `index.html.erb` file might look like: ```html <!-- app/views/books/index.html.erb --> <h1>Book List</h1> <table> <thead> <tr> <th>Title</th> <th>Author</th> <th>Publish Date</th> <th>Actions</th> </tr> </thead> <tbody> <% @books.each do |book| %> <tr> <td><%= book.title %></td> <td><%= book.author %></td> <td><%= book.published_at.strftime("%B %d, %Y") %></td> <td> <%= link_to "Show", book_path(book) %> <%= link_to "Edit", edit_book_path(book) %> <%= link_to "Delete", book_path(book), method: :delete, data: {confirm: "Are you sure?"} %> </td> </tr> <% end %> </tbody> </table> ``` **Step 7: Run the Application** Open your terminal and start the Rails server: ```bash rails s ``` Open a web browser and navigate to `http://localhost:3000/books`. You should see a list of books (which will be empty initially). **Practical Takeaways:** * Create a Rails application with a single model, controller, and view. * Define routes for CRUD operations using the `resources` method. * Use migrations to create and modify the database schema. * Apply form helpers and submit form data to create new records. * Display and manage data using views and controllers. **What to Do Next:** In the next topic, we will explore how to work with databases and Active Record in Ruby on Rails. Please feel free to ask for help or leave comments if you have any questions or need further clarification. If you want to learn more about Ruby on Rails and its various features, feel free to explore the following resources: * [Ruby on Rails Official Documentation](https://guides.rubyonrails.org/) * [Rails API Documentation](https://api.rubyonrails.org/) * [Rails Tutorial by Michael Hartl](https://www.railstutorial.org/)