Decorator Pattern Vs Inheritance

[Shankar sanjay]

Hi,

Can anyone please tell that How Decorator pattern differs from Inheritance?, for me Decorator Pattern looks like inheritance concept.

Regards,

Sankar. S

[Jelle Klap]

The decorator pattern allows you to add behaviour dynamically at runtime to an instance of a particular class, whereas inheritance adds behaviour at compile time.
You can make use of inheritance when applying the decorator pattern, although that's not always a necessity.
So it's perfectly ok to use both inheritance and composition when creating a decorator class, if you don't have a common interface you can implement.
Or if you want to create an (abstract) "base" decorator class.

[Muhammad Khojaye]

Jelle Klap wrote:
You can make use of inheritance when applying the decorator pattern, although that's not always a necessity.

Adding new behavior to the base class by creating separate subclass for every possible combination could let to a maintenance nightmare. There are better alternative available to Inheritance.