m09-domain

What problem does it solve?

This Skill helps avoid common domain-design mistakes in C++ such as confusing identity with value, accidentally enabling object slicing, exposing implementation details in headers, and allowing invalid object states through public fields.

Core Features & Use Cases

• Clear Value vs Entity guidance: Decide when a type should be a copyable value object versus a non-copyable entity identified by an ID.
• Ownership and Aggregates: Advice on owning children with unique_ptr or vectors and defining aggregate roots.
• APIs and Encapsulation: Recommendations for enforcing invariants via private data and public methods, using Pimpl to reduce header coupling, and using strong typed IDs instead of raw integers.
• Use Case: Design a User aggregate that holds Value Objects for Name and Address, uses a strong UserId, deletes copy operations on the Entity, and exposes repository interfaces for persistence.

Quick Start

Design a User type by making the ID a strong type, treating Name and Address as value objects, deleting the User copy constructor while allowing move, encapsulating invariants in private members exposed through methods, and owning child entities with unique_ptr.