DesignPatterns

Intro

• A design pattern systematically names, explains, and evaluates an important and recurring design problem and its solution.
• They capture the intent behind a design by identifying objects, collaborations, and distributions of responsibilities.
  • They capture static and dynamic structures of successful solutions to problems.
• Patterns support reuse of software architecture and design.
• They give software engineers a vocabulary with which to describe their designs.
• Patterns solve design problems such as:
  • Finding appropriate classes to solve a problem.
  • Determining how abstract or how concrete a class should be.
  • Specifying interfaces of classes, architectures, and binary components.
  • Designing for change.
• Patterns are not code-reuse they are experience reuse !

Facade

Intent

• Provide a common interface to a set of interfaces within a subsystem.
• Defines a higher level interface to make the subsystem interfaces easier to use.

Motivation

• Provide a simplified interface.

Consequences

• Shield clients from myriad subsystem components - hence promote weak coupling between clients and subsystems.
• Therefore, Subsystems can be changed without the client being affected.