**Course Title:** Ruby Programming: From Basics to Advanced Techniques **Section Title:** Introduction to Ruby on Rails **Topic:** Creating a simple Rails application **Creating a Simple Rails Application** In this topic, we will cover the basics of creating a simple Rails application from scratch. By the end of this topic, you will have a fully functional Rails application that you can use to build more complex applications. **Prerequisites:** * You should have a basic understanding of Ruby and its syntax. * You should have a working development environment set up with Ruby and Rails installed. **Step 1: Create a New Rails Application** To create a new Rails application, open your terminal and run the following command: ```bash rails new my_app ``` This will create a new directory called `my_app` with the basic structure for a Rails application. **Step 2: Explore the Rails Application Structure** Let's take a look at the structure of the `my_app` directory: ```bash my_app/ app/ controllers/ models/ views/ config/ db/ Gemfile Gemfile.lock ``` Here's a brief explanation of each directory: * `app/`: This directory contains the application code, including controllers, models, and views. * `controllers/`: This directory contains the controller code, which handles HTTP requests and responds with HTTP responses. * `models/`: This directory contains the model code, which represents the data in the application. * `views/`: This directory contains the view code, which is used to render the user interface. * `config/`: This directory contains configuration files for the application. * `db/`: This directory contains the database schema. * `Gemfile`: This file specifies the dependencies for the application. * `Gemfile.lock`: This file specifies the locked dependencies for the application. **Step 3: Run the Rails Server** To run the Rails server, navigate to the `my_app` directory and run the following command: ```bash rails server ``` This will start the Rails server, and you can access your application at `http://localhost:3000`. **Step 4: Create a New Controller** To create a new controller, run the following command: ```bash rails generate controller Welcome ``` This will create a new file called `welcome_controller.rb` in the `app/controllers` directory. **Step 5: Define a New Action** To define a new action, open the `welcome_controller.rb` file and add the following code: ```ruby class WelcomeController < ApplicationController def index render text: "Hello, World!" end end ``` This code defines a new action called `index` that renders the text "Hello, World!". **Step 6: Map the New Action to a Route** To map the new action to a route, open the `config/routes.rb` file and add the following code: ```ruby Rails.application.routes.draw do get '/welcome', to: 'welcome#index' end ``` This code maps the `index` action to the `/welcome` route. **Step 7: Run the Rails Server Again** To run the Rails server again, navigate to the `my_app` directory and run the following command: ```bash rails server ``` This will start the Rails server, and you can access your application at `http://localhost:3000/welcome`. **Practical Takeaways:** * You now have a fully functional Rails application that you can use to build more complex applications. * You have learned how to create a new controller and define a new action. * You have learned how to map a new action to a route. * You have learned how to run the Rails server and access your application. **Exercise:** * Create a new controller and define a new action that renders a simple HTML page. * Map the new action to a route and run the Rails server. * Access your application at the mapped route and verify that the action is working correctly. **Leave a comment or ask for help if you have any questions or need further clarification on any of the steps!** **Next Topic:** Understanding routing in Rails applications. From: Advanced Rails: Routing and Views.