writing-affordances

Refactor fat Rails models by extracting PORO wrappers that group 3+ related methods under a domain noun. This creates a focused affordance API, keeping the parent model lean and converting clustered prefixes into clean calls like card.entropy.auto_clean_at.

An affordance is a PORO wrapper that clusters 3+ methods coordinating multiple associations around a single noun. Use this pattern when methods share a prefix and form a cohesive API, ensuring focused domain logic and improved testability.

Yes, you can use an optional Rails concern to provide infrastructure and an explicit entry method for the PORO affordance class. The concern returns the PORO instance, keeping the parent model lean while exposing the domain noun API.

The best way to extract domain logic is identifying 3+ methods sharing a prefix, creating a PORO named after the concept, and wiring an entry method on the parent model. This affordance approach ensures reusable, testable operations separated from the fat model.

You should not use a PORO affordance when fewer than 3 methods share a prefix or when the methods do not coordinate multiple associations to form a cohesive API. The pattern requires enough related operations to justify extracting a dedicated domain noun wrapper.