Decorator (aka Wrapper)

Intent

• Attach additional responsibilities to an object dynamically.

• Decorators provide a flexible alternative to subclassing for extending functionality.

Problem

• How can responsibilities be added to an object dynamically?

• How can the functionality of an object be extended at run-time?

Solution

• Define separate Decorator objects that add responsibilities to an object.

• Work through Decorator objects to extend the functionality of an object at run-time.

Advantages

✅ Provides a flexible alternative to subclassing. ✅ Allows an open-ended number of added functionalities.

Disadvantages

❌ Provides no reliability on object identity, due to transparent enclosure.

Notes

• A nice article on decorator and how to use them for embellishment.