Design PatternsCreational patterns giải quyết vấn đề tạo object một cách linh hoạt. Cách chọn:
- Singleton: cần đúng một instance shared toàn app (logger, config) — nhưng ưu tiên DI container thay vì tự implement.
- Factory Method: framework cần cho phép subclass override cách tạo object.
- Abstract Factory: cần tạo nhóm object liên quan phải consistent với nhau.
- Builder: object có nhiều optional params hoặc construction process phức tạp nhiều bước.
- Prototype: clone nhanh hơn tạo mới (object expensive to initialize).
- Object Pool: object expensive to create và cần reuse ở high throughput.
Quy tắc thực tế: bắt đầu simple (new Constructor()), refactor sang pattern khi thấy pain point rõ ràng. YAGNI áp dụng cho cả design patterns.
Creational patterns solve the problem of creating objects flexibly.
- How to choose: use Singleton when exactly one shared instance is needed app-wide (logger, config) — but prefer a DI container over a hand-rolled Singleton; use Factory Method when a framework needs to let subclasses override how objects are created; use Abstract Factory when creating a group of related objects that must be consistent with each other; use Builder when an object has many optional parameters or a complex multi-step construction process; use Prototype when cloning is faster than creating from scratch; use Object Pool when objects are expensive to create and need to be reused.
- Practical rule: start simple (
new Constructor()), and refactor to a pattern only when a clear pain point emerges. - Over-engineering with patterns from the start is a common mistake — YAGNI applies to design patterns too.