Software Design & Architecture, Study notes of Software Development Methodologies

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MIRPUR UNIVERSITY OF SCIENCE AND TECHNOLOGY

DEPARTMENT OF SOFTWARE ENGINEERING

Software Design & Architecture 1

Software Design & Architecture (Lecture # 25) Decorator Design Pattern Saba Zafar (Lecturer) Date: 8 September, 2020

DECORATOR PATTERN - DESIGN PATTERN

• Name: Decorator
• Problem: You want to add behavior or state to individual objects at run-time. Inheritance is not feasible because it is static and applies to an entire class
• Solution:
  • The decorator pattern enables us to add new or additional behavior to an object during runtime, depending on the situation
  • Decorators have the same super-type as the objects they decorate
  • One or more decorator objects can be used to wrap an object

DECORATOR PATTERN - DESIGN PATTERN

• This pattern creates a decorator class which wraps the original class and provides additional functionality
• The decorator adds its own behavior either before and/or after delegating to the object it decorates
• Objects can be decorated at any time, so we can decorate objects dynamically at runtime with as many decorators as we like.

DECORATOR PATTERN - DESIGN PATTERN

• But the Decorator pattern suggests giving the client the ability to specify whatever combination of "features" is desired.
• This flexibility can be achieved with the following design

DECORATOR PATTERN - DESIGN PATTERN Example: Assault gun is a deadly weapon on it's own. But you can apply certain "decorations" to make it more accurate, silent and devastating

Software Design & Architecture 10 DECORATOR PATTERN - EXAMPLE EXAMPLE: Pizza Topping

THANKS

Software Design & Architecture 11