midDDD
What is a Factory in DDD?
Updated Apr 28, 2026
Short answer
A pattern used to encapsulate the complexity of creating complex Aggregates or Entities, ensuring they start in a valid state.
Deep explanation
Mid-level DDD focuses on the interaction between components. Aggregate Roots protect business rules (Invariants). If an Order can't have more than 10 items, the Order Aggregate Root rejects the 'AddItem' call. Domain Events help decouple these systems.
Real-world example
A banking app where a 'Transfer' triggers an 'Email Notification' via a Domain Event.
Common mistakes
- Injecting Repositories into Entities, which couples the model to the persistence layer.
Follow-up questions
- How large should an Aggregate be?