Purpose
This glossary defines Ruby on Rails terminology used throughout the
Engineering Knowledge Framework.
Rails-specific terms defined here are authoritative across the
repository. Foundational engineering terms are defined in the
Engineering Glossary.
Glossary
ActiveRecord
| Property | Value |
|---|
| Definition | The ORM (Object-Relational Mapping) layer in Rails that |
| maps database tables to Ruby objects and provides |
| query, persistence and validation capabilities. |
| Context | ActiveRecord is the default model layer in Rails. It |
| implements the Active Record pattern where a class |
| wraps a database table. |
| Related | Migration, Model |
| References | Rails Engineering Handbook |
Concern
| Property | Value |
|---|
| Definition | A module used to extract shared behaviour from models or |
| controllers, typically placed in app*models*concerns* |
| or app*controllers*concerns*. |
| Context | Concerns are Rails' mechanism for sharing behaviour via |
| modules. Use them for cross-cutting concerns, but prefer |
| service objects for complex business logic. |
| Related | Service Object |
| References | Rails Engineering Handbook |
Controller
| Property | Value |
|---|
| Definition | The component in MVC that handles incoming HTTP requests, |
| invokes business logic and renders responses. |
| Context | Controllers should be thin. Business logic belongs in |
| models, service objects or other domain classes. |
| Related | Model, View |
| References | Rails Engineering Handbook |
| Property | Value |
|---|
| Definition | A plain Ruby object that encapsulates form validation |
| and data processing for forms that do not map directly |
| to a single model. |
| Context | Form objects are used when a form collects data for |
| multiple models or has validation logic that does not |
| belong to any single model. |
| Related | Service Object |
| References | Rails Engineering Handbook |
Migration
| Property | Value |
|---|
| Definition | A Ruby class that describes a change to the database |
| schema, allowing incremental, version-controlled schema |
| evolution. |
| Context | Migrations are the Rails way to manage database schema |
| changes. Each migration should change one logical thing |
| and be reversible. |
| Related | ActiveRecord |
| References | Rails Engineering Handbook |
Model
| Property | Value |
|---|
| Definition | The component in MVC that represents business data and |
| logic. In Rails, models typically inherit from |
| ActiveRecord::Base. |
| Context | Models encapsulate domain logic, validations, |
| associations and queries. Keep them focused on |
| a single responsibility. |
| Related | ActiveRecord, Controller, View |
| References | Rails Engineering Handbook |
Presenter
| Property | Value |
|---|
| Definition | An object that encapsulates presentation logic, |
| extracting it from views into a testable class. |
| Context | Presenters wrap model objects with view-specific methods. |
| They keep views clean and make presentation logic |
| testable without slow feature specs. |
| Related | View, Service Object |
| References | Rails Engineering Handbook |
Query Object
| Property | Value |
|---|
| Definition | A plain Ruby object that encapsulates a complex database |
| query, extracting it from the model into a separate |
| class. |
| Context | Query objects keep models clean when queries become |
| complex. They are named after the query they perform. |
| Related | ActiveRecord, Service Object |
| References | Rails Engineering Handbook |
Service Object
| Property | Value |
|---|
| Definition | A plain Ruby object that encapsulates a single |
| business operation, typically with one public method. |
| Context | Service objects are the primary pattern for extracting |
| complex operations from controllers and models. They |
| are easy to test and can be reused across entry points. |
| Related | Form Object, Query Object, Concern |
| References | Rails Engineering Handbook |
View
| Property | Value |
|---|
| Definition | The component in MVC responsible for rendering the user |
| interface, typically using ERB or other template |
| languages. |
| Context | Views should contain minimal logic. Presentation logic |
| belongs in presenters, decorators or helpers. |
| Related | Controller, Model |
| References | Rails Engineering Handbook |