**Course Title:** Mastering Ruby on Rails: Building Scalable Web Applications **Section Title:** File Uploads and Active Storage **Topic:** Handling file uploads in Rails applications **Introduction** In this topic, we will explore how to handle file uploads in Rails applications. File uploads are a common requirement in web applications, and Rails provides a robust way to handle them using Active Storage. In this topic, we will cover the basics of file uploads, how to use Active Storage, and how to implement file upload functionality in your Rails application. **Key Concepts** * File uploads: The process of sending files from a client (e.g., a web browser) to a server. * Active Storage: A gem that provides a simple way to store and manage files in your Rails application. * File upload forms: HTML forms that allow users to select files to upload. * File upload handlers: Rails controllers that handle file uploads. **Prerequisites** * Familiarity with Rails and its basic concepts. * Understanding of HTML forms and file upload functionality. **Step 1: Setting up Active Storage** To use Active Storage, you need to add the `active_storage` gem to your Gemfile and run `bundle install`. You also need to configure Active Storage by running `rails active_storage:install`. ```ruby # Gemfile gem 'active_storage', '~> 7.0' ``` ```bash # Run the command to install Active Storage bundle install ``` ```bash # Run the command to configure Active Storage rails active_storage:install ``` **Step 2: Creating a File Upload Form** To create a file upload form, you need to add a `file` input field to your HTML form. You can use the `input` tag with the `type` attribute set to `file`. ```html <!-- file_upload_form.html.erb --> <%= form_tag({ action: '/upload', method: 'post' }) do %> <%= label_tag :file %> <%= file_field_tag :file %> <%= submit_tag 'Upload' %> <% end %> ``` **Step 3: Handling File Uploads** To handle file uploads, you need to create a file upload handler. A file upload handler is a Rails controller that handles file uploads. You can create a file upload handler by creating a new controller and adding a `post` action. ```ruby # controllers/upload_controller.rb class UploadController < ApplicationController def create file = params[:file] # Process the file upload # ... end end ``` **Step 4: Storing Files with Active Storage** To store files with Active Storage, you need to use the `store` method. The `store` method takes a file object as an argument and stores it in Active Storage. ```ruby # controllers/upload_controller.rb class UploadController < ApplicationController def create file = params[:file] # Store the file in Active Storage file.store! # ... end end ``` **Step 5: Retrieving Files from Active Storage** To retrieve files from Active Storage, you need to use the `url_for` method. The `url_for` method takes a file ID as an argument and returns the URL of the file. ```ruby # controllers/upload_controller.rb class UploadController < ApplicationController def show file_id = params[:id] # Retrieve the file from Active Storage file = ActiveStorage::Blob.find(file_id) # ... end end ``` **Conclusion** In this topic, we covered the basics of file uploads in Rails applications and how to use Active Storage to manage file uploads. We also covered how to create file upload forms, handle file uploads, store files with Active Storage, and retrieve files from Active Storage. **Practical Takeaways** * Use the `active_storage` gem to store and manage files in your Rails application. * Create file upload forms using HTML forms with a `file` input field. * Handle file uploads by creating a file upload handler. * Store files with Active Storage using the `store` method. * Retrieve files from Active Storage using the `url_for` method. **Additional Resources** * [Active Storage documentation](https://guides.rubyonrails.org/active_storage_overview.html) * [Rails Active Storage API](https://api.rubyonrails.org/classes/ActiveStorage/Blob.html) **Leave a comment or ask for help if you have any questions or need further clarification on any of the topics covered in this topic.**