query_objects.md

Query Objects

Introduction

Query Objects are useful to extract ActiveRecord scopes or complex SQL queries into their own classes, which would otherwise clutter ActiveRecord models.

Conventions

• Queries go under the app/queries directory.
• Query class name should have suffix Query (e.g. AuthorsQuery).
• Query class name should start with primary model name used in query in plural form (e.g. AuthorsWithBooksQuery).
• Consider creating base query class for the model (e.g. AuthorsQuery) and subclasses for more specific cases (e.g. AuthorsWithBooksQuery < AuthorsQuery).
• Query object should return ActiveRecord::Relation object.
• Use scope none for the cases when respond with empty collection is required.
• Define only one public method #perform.
• Use auxiliary_rails gem.

References

• Delegating to Query Objects through ActiveRecord scopes
• Essential RubyOnRails patterns — part 2: Query Objects
• https://github.com/andypike/rectify#query-objects
• https://github.com/infinum/rails-handbook/blob/master/Design%20Patterns/Query%20Objects.md