The decorator design pattern is a structural pattern that allows for the dynamic and flexible addition of functionalities to objects through composition, adhering to the open/closed principle. An example illustrates this concept with a house where an additional floor can be added without altering the original structure, demonstrating the incremental enhancement of an object. The pattern enables the flexible composition of behaviors while complying with design principles.

1. Decorator
Design
Pattern

2. Introduction
Example
Class Diagram
Implementation
Table of contents
01
02
03
04

3. Introductio
n
Definition and Purpose
01

4. Definition
The Decorator pattern is a structural
design pattern that allows adding
functionalities to objects dynamically
and flexibly. It is achieved through
composition instead of inheritance,
enabling the extension of an object's
capabilities without modifying its base
code. In other words, the Decorator
provides a way to add or remove
responsibilities to existing objects
incrementally and consistently.

5. Purpose
• Extend object functionalities
dynamically.
• Enable flexible composition of
behaviors.
• Comply with the Open/Closed
Principle (OCP) by facilitating
extension without modifying
existing code.

6. Example
Real-World Example
02

7. Real-World Example
Original house Original house with a
decorator (the
additional floor is built
on top of
original structure)
Applying an additional
decorator on top of
the existing decorator
and
modifying the house
(now painting the
Suppose that you own a single-story house, and you decide to build an additional
floor on top of it. You may not want to change the architecture of the ground
floor, but you may want to employ a new design for the newly added floor that
can fit on top of the existing architecture.

8. Figure 1 Figure 2 Figure 3
The case shown in Figure 3 is optional. You can use an existing decorator object
to enhance the behavior, or you can create a new decorator object and add the
new behavior to it. In step 2, you could also directly paint the original house.
You don’t need to start painting once the new floor is added.
Real-World Example

9. Class
Diagram
Class Diagram and Solution Explorer
03

12. Implementati
on
04