kimtth Goal: code whose responsibilities and dependencies are clear and stable.
Use for:
- reviewing class responsibilities and coupling
- guiding a refactor toward maintainable structure
- explaining why a design is hard to change
Workflow:
- Single responsibility: one reason to change per unit.
- Open/closed: extend behavior without modifying stable code.
- Liskov: subtypes must honor the base type's contract.
- Interface segregation: small interfaces over fat ones.
- Dependency inversion: depend on abstractions, not details.
- Apply only where it removes real pain.
Smells the principles address:
- god classes and shotgun surgery (SRP)
- modifying core code for every new case (OCP)
- subclasses that break expectations (LSP)
- clients forced to depend on unused methods (ISP)
- high-level code chained to low-level details (DIP)
Rules:
- principles are guidance, not dogma; avoid over-abstraction
- prefer the simplest design that stays changeable
- introduce abstraction at the second real use, not the first
- a clear, cohesive unit beats a clever hierarchy