**Course Title:** Ruby Programming: From Basics to Advanced Techniques **Section Title:** Working with Databases in Rails **Topic:** Implement database interactions in the Rails application using ActiveRecord. **Objective:** By the end of this lab, you will be able to implement database interactions in a Rails application using ActiveRecord, including creating, reading, updating, and deleting (CRUD) operations. **Introduction** ActiveRecord is a powerful ORM (Object-Relational Mapping) tool in Rails that allows you to interact with databases using Ruby code. In this lab, you will learn how to use ActiveRecord to perform CRUD operations in a Rails application. **Step 1: Setting up the Database** Before you can start interacting with the database, you need to set up the database in your Rails application. Make sure you have already created a Rails application and have run the command `rails db:migrate` to set up the database. **Step 2: Creating a Model** To interact with the database using ActiveRecord, you need to create a model. The model represents a table in the database. For example, let's say we want to create a model called `Book`. To create a model, run the following command: ```bash rails generate model Book title:string author:string ``` This will create a new file called `book.rb` in the `app/models` directory. **Step 3: Running the Migration** After creating the model, you need to run the migration to create the corresponding table in the database. To run the migration, run the following command: ```bash rails db:migrate ``` **Step 4: Performing CRUD Operations** Now that we have set up the database and created a model, we can start performing CRUD operations. * **Creating a new record:** To create a new record, you can use the `create` method: ```ruby Book.create(title: "The Great Gatsby", author: "F. Scott Fitzgerald") ``` * **Reading records:** To read all records, you can use the `all` method: ```ruby books = Book.all ``` * **Updating a record:** To update a record, you can use the `update` method: ```ruby book = Book.find(1) book.update(title: "The Catcher in the Rye") ``` * **Deleting a record:** To delete a record, you can use the `destroy` method: ```ruby book = Book.find(1) book.destroy ``` **Example Use Cases** Here are some example use cases of using ActiveRecord to perform CRUD operations: * **Creating a new user account:** To create a new user account, you can use the `create` method: ```ruby User.create(name: "John Doe", email: "johndoe@example.com") ``` * **Displaying all books:** To display all books, you can use the `all` method: ```ruby books = Book.all ``` * **Updating a book title:** To update a book title, you can use the `update` method: ```ruby book = Book.find(1) book.update(title: "The Lord of the Rings") ``` * **Deleting a book:** To delete a book, you can use the `destroy` method: ```ruby book = Book.find(1) book.destroy ``` **Tips and Best Practices** * **Use `find` with caution:** When using `find` to retrieve a record, make sure to handle the case where the record does not exist. You can use `find_by` instead, which returns `nil` if the record does not exist. * **Use `invalid?` to check if a record is valid:** Before saving a record, use `invalid?` to check if the record is valid. This can help prevent errors. * **Use transactions:** When performing multiple database operations, use transactions to ensure that either all or none of the operations are committed. **Conclusion** In this lab, you learned how to implement database interactions in a Rails application using ActiveRecord. You learned how to create, read, update, and delete records using ActiveRecord methods. You also learned about tips and best practices for using ActiveRecord. **Leave a comment below if you have any questions or need help with this lab.** Next topic: [Preparing a Rails application for production](https://guides.rubyonrails.org/deployment.html). Additional resources: * [ActiveRecord documentation](https://api.rubyonrails.org/classes/ActiveRecord.html) * [Rails documentation on database interactions](https://edgeguides.rubyonrails.org/activerecord_basics.html)