37signals-concerns

To extract shared Rails logic into concerns, identify duplicated model or controller behavior such as validations and scopes, move it into a self-contained module using ActiveSupport::Concern, and include that concern in the relevant classes for clean horizontal composition.

Organize shared controller logic in Rails 8 by extracting repeated behavior into self-contained concerns under app/controllers/concerns, using ActiveSupport::Concern to DRY up controllers and enable clean modular composition across your application.

Use ActiveSupport::Concern for Rails code organization when multiple models or controllers share behavior like validations, associations, scopes, and callbacks, requiring extraction into cohesive horizontal modules for clean composition and reuse.

Yes, extracting concerns works with both Rails models and controllers, organizing shared behavior under app/models/[model]/concerns and app/controllers/concerns respectively to drive horizontal reuse across your entire Rails 8+ application.

Refactor duplicated Rails model callbacks into a shared mixin by moving the repeated callback logic into an independent concern using ActiveSupport::Concern, then including that concern in relevant models to achieve clean composition and horizontal reuse.

Rails concerns promote horizontal reuse but require careful organization to avoid tangled dependencies; concerns should remain self-contained and cohesive, documenting clear include points in SKILL.md to prevent complex interdependencies across models and controllers.