layout, title, folder, permalink, categories, tags
| layout | title | folder | permalink | categories | tags | |||
|---|---|---|---|---|---|---|---|---|
| pattern | Decorator | decorator | /patterns/decorator/ | Structural |
|
Also known as
Wrapper
Intent
Attach additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.
Applicability
Use Decorator
- to add responsibilities to individual objects dynamically and transparently, that is, without affecting other objects
- for responsibilities that can be withdrawn
- when extension by subclassing is impractical. Sometimes a large number of independent extensions are possible and would produce an explosion of subclasses to support every combination. Or a class definition may be hidden or otherwise unavailable for subclassing