The document discusses the decorator design pattern. It defines the decorator pattern as allowing behavior to be added to individual objects without affecting other objects from the same class. It describes how the decorator pattern works by subclassing the original component class into a decorator class and redirecting component methods to the underlying component pointer. Examples of using the decorator pattern for a coffee shop and beauty salon are provided, with pros and cons discussed.

1. DESIGN PATTERN
READING GROUP –
DECORATOR PATTERN
2014/May/30
Vincent Chu

2. AGENDA
What is Decorator Pattern?
Examples
Conclusion

3. WHAT IS DECORATOR
PATTERN?
Definition
In object-oriented
programming, the
decorator pattern (also
known as Wrapper, an
alternative naming shared
with the Adapter pattern)
is a design pattern that
allows behavior to be
added to an individual
object, either statically or
dynamically, without
affecting the behavior of
other objects from the
same class.
UML

4. WHAT IS DECORATOR
PATTERN?
Implementation
1. Subclass the original "Component" class into a
"Decorator" class (see UML diagram);
2. In the Decorator class, add a Component pointer as a
field;
3. Pass a Component to the Decorator constructor to
initialize the Component pointer;
4. In the Decorator class, redirect all "Component"
methods to the "Component" pointer; and
5. In the ConcreteDecorator class, override any
Component method(s) whose behavior needs to be
modified.

5. EXAMPLES
Cup of Joe Beauty Salon

6. EXAMPLE – COFFEE

7. EXAMPLE – BEAUTY SALON
http://www.slideshare.net/eolexe/omg-patterns-
ltdecorator-by-max-titov
Page 3

8. CONCLUSION
Consider following pattern before you choice Decorator
 Adapter
 Proxy
 Strategy
 Composite

9. CONCLUSION
Pros
1) The cure of ugly code
2) Composition over
inheritance
3) Add behavior at runtime
without class
modification
4) Behavior can be reuse
Cons
1) Tons of small classes
2) Could be not obvious for
other developers

10. REFERENCE
Wikipedia -
http://en.wikipedia.org/wiki/Decorator_pattern
Photo & Conclusion -
http://www.slideshare.net/eprafulla/01-introduction-
and-decorator-pattern
Beauty Salon - http://www.slideshare.net/eolexe/omg-
patterns-ltdecorator-by-max-titov
Cup of Joe -
http://www.slideshare.net/melbournepatterns/phani-
kumar-decorator-pattern
Coffee -
http://internshipblogg.wordpress.com/2012/06/13/dec
orator-pattern-power-of-extension/

11. THANKS FOR YOUR TIME!