Enforcing Business Rules with Invariants
Learn to encode critical business rules as invariants inside entities so the domain can never enter an invalid state.
Rules That Must Always Hold
Beyond use-case logic, a domain has rules that must be true at all times. An account balance never goes below zero; an order always has at least one line item.
These are invariants, and the core should make them impossible to violate.
Entity Invariants vs Use-Case Rules
Two layers of rules exist:
- Entity invariants: always true regardless of operation (Enterprise Business Rules).
- Use-case rules: govern a specific workflow (Application Business Rules).
Invariants belong inside the entity itself.
All lessons in this course
- Designing Business Entities
- Implementing Use Cases (Interactors)
- Input and Output Ports
- Enforcing Business Rules with Invariants