Nguyen D' Quach

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Design Patterns

• Nguyen D. Quach
• Spring 07

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Outline

• Definition History
• Pattern Categories
• Examples
• Conclusion Summary

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Design Pattern

• Definition
• A general repeatable solution to a common problem
  in object oriented software design.
• Not an algorithm
• History
• Originated as an architectural concept by
  Christopher Alexander
• Gained popularity after the book Design Patterns
  Elements of Reusable Object-Oriented Software by
  the Gang of Four (GoF).

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Pattern Categories

• Creational Patterns - Solving problems related to
  creating object instances
• Singleton, builder, factory, etc
• Structural Patterns - Solving problems relating
  structural relationships between parts of an OO
  system.
• Adapter, façade, bridge, composite, etc
• Behavioral Patterns solving problem that
  requires a particular type of behavoral or
  operational abstractions.
• decorator, observer, State, visitor, etc

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Example

• Nonfunctional Requirements give a clue for the
  use of Design Patterns
• Text manufacturer independent, device
  independent, must support a family of products
• Abstract Factory Pattern
• Text must interface with an existing object
• Adapter Pattern
• Text must deal with the interface to several
  systems, some of them to be developed in the
  future, an early prototype must be
  demonstrated
• Bridge Pattern

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Note

• Design Patterns can be complicated.
• Get more familiar through experience
• Each pattern has its advantages and
  disadvantages.
• Good to have a reference book.
• Simplicity over complexity

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Summary

• Design Pattern definition and history
• How non-functional requirements give clues to
  selecting the right design pattern.
• Pattern Categories Creational, Structural, and
  Behavioral patterns.

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Refererences

• Gamma, Erich Richard Helm, Ralph Johnson, and
  John Vlissides (1995). Design Patterns Elements
  of Reusable Object-Oriented Software, hardcover,
  395 pages, Addison-Wesley. ISBN 0-201-63361-2. 
• Bernd Bruegge Allen Dutoit. Conquering Complex
  and Changing Systems
• Wikipedia
• http//en.wikipedia.org/wiki/Design_pattern_(compu
  ter_science)
• Alan Shalloway James R. Trott. Design Patterns
  Explained A new Perspective on Object-Oriented
  Design

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Question?