Active Record pattern in Ruby on Rails - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the Active Record pattern in Rails?

It is a design pattern where each model class wraps a database table and provides methods to create, read, update, and delete records. It connects objects and database rows directly.

beginner

How does Active Record in Rails simplify database interactions?

It lets you work with Ruby objects instead of writing SQL queries. You can call methods like .find, .save, and .destroy on model instances to manage data.

beginner

What method would you use to get all records of a model in Active Record?

You use the .all method. For example, User.all returns all users from the users table as Ruby objects.

intermediate

Explain the relationship between a Rails model and the database in the Active Record pattern.

Each Rails model corresponds to a database table. Each instance of the model represents a row in that table. The model handles data validation, querying, and persistence.

intermediate

What happens when you call save on an Active Record model instance?

If the object is new, it inserts a new row in the database. If it already exists, it updates the existing row with any changed attributes.

In Rails Active Record, which method fetches a record by its ID?

A .get

B .fetch

C .find

D .select

The .find method retrieves a record by its primary key (usually ID).

What does User.new do in Active Record?

A Creates a new user object but does not save it to the database

B Fetches a user from the database

C Deletes a user record

D Updates a user record

User.new creates a new instance in memory but does not save it until save is called.

Which Active Record method removes a record from the database?

A .destroy

B .remove

C .delete

D .erase

.destroy deletes the record and runs callbacks, while .delete removes it without callbacks.

How does Active Record know which database table to use for a model named Article?

A You must specify the table manually

B It uses the pluralized lowercase name: articles

C It uses the model name as is: Article

D It uses a random table

Active Record automatically maps Article to the articles table by pluralizing and lowercasing the model name.

What is the main benefit of using the Active Record pattern in Rails?

A It disables validations

B It requires writing raw SQL for every query

C It only works with NoSQL databases

D It hides database details and lets you work with Ruby objects

Active Record abstracts database access so you can use Ruby code instead of SQL, making development easier and safer.

Describe how the Active Record pattern connects Ruby objects to database tables in Rails.

Think about how a model and its instances relate to the database.

Explain what happens when you create a new model instance and call save in Rails Active Record.

Focus on the lifecycle of a model object from creation to database storage.