Active Record CallbacksThis guide teaches you how to hook into the life cycle of your Active Record objects.After reading this guide, you will know: When certain events occur during the life of an Active Record object. How to register, run, and skip callbacks that respond to these events. How to create relational, association, conditional, and transactional callbacks. How to create objects that encapsulate common behavior for your callbacks to be reused.| Ruby on Rails Guides
Active Support Core ExtensionsActive Support is the Ruby on Rails component responsible for providing Ruby language extensions and utilities.It offers a richer bottom-line at the language level, targeted both at the development of Rails applications, and at the development of Ruby on Rails itself.After reading this guide, you will know: What Core Extensions are. How to load all extensions. How to cherry-pick just the extensions you want. What extensions Active Support provides.| Ruby on Rails Guides
An object that wraps a row in a database table or view, encapsulates the database access, and adds domain logic on that data.| martinfowler.com
Active Record MigrationsMigrations are a feature of Active Record that allows you to evolve your database schema over time. Rather than write schema modifications in pure SQL, migrations allow you to use a Ruby Domain Specific Language (DSL) to describe changes to your tables.After reading this guide, you will know: Which generators you can use to create migrations. Which methods Active Record provides to manipulate your database. How to change existing migrations and update your schema. How ...| Ruby on Rails Guides
Active Record AssociationsThis guide covers the association features of Active Record.After reading this guide, you will know how to: Declare associations between Active Record models. Understand the various types of Active Record associations. Use the methods added to your models by creating associations.| Ruby on Rails Guides
Testing Rails ApplicationsThis guide covers built-in mechanisms in Rails for testing your application.After reading this guide, you will know: Rails testing terminology. How to write unit, functional, integration, and system tests for your application. Other popular testing approaches and plugins.| Ruby on Rails Guides
Active Record Query InterfaceThis guide covers different ways to retrieve data from the database using Active Record.After reading this guide, you will know: How to find records using a variety of methods and conditions. How to specify the order, retrieved attributes, grouping, and other properties of the found records. How to use eager loading to reduce the number of database queries needed for data retrieval. How to use dynamic finder methods. How to use method chaining to use multiple Acti...| Ruby on Rails Guides
Active Record ValidationsThis guide teaches you how to validate the state of objects before they go into the database using Active Record's validations feature.After reading this guide, you will know: How to use the built-in Active Record validation helpers. How to create your own custom validation methods. How to work with the error messages generated by the validation process.| Ruby on Rails Guides
