gof-factory

One-line summary

Centralize the choice of which concrete class to instantiate, hiding it from clients — in three flavors of increasing scope: Simple Factory (one method picks a type), Factory Method (subclasses pick a type), Abstract Factory (a family of related types).

When to use this skill

• Client code is full of new ConcreteX() decisions and the choice depends on input data, configuration, or environment.
• Two parallel hierarchies need to pick matched implementations together (e.g., a NYStylePizzaStore should produce NYStyleDough, NYStyleSauce — that's Abstract Factory).
• Subclasses should decide which concrete type to instantiate while sharing the surrounding workflow — Factory Method.
• Construction itself has invariants that the constructor alone can't enforce.

When NOT to use this skill

• Only one concrete type exists; just call its constructor.
• A simple top-level function (fun parsePayment(json): Payment) is enough — naming a class *Factory for a single function adds nothing.
• Construction is genuinely trivial and adding indirection just because "factories are best practice" is ceremony.

Core content