Tuesday, 14 June 2011

Design Patterns


Design patterns are recurring solutions to software design problems you find again and again in real-world application development.
Patterns are about design and interaction of objects, as well as providing a communication platform concerning elegant, reusable solutions to commonly encountered programming challenges.
The Gang of Four (GoF) patterns are generally considered the foundation for all other patterns. They are categorized in three groups: Creational, Structural, and Behavioral.

 Creational Patterns
Creates an instance of several families of classes
Separates object construction from its representation
Creates an instance of several derived classes
A fully initialized instance to be copied or cloned
A class of which only a single instance can exist

  Structural Patterns
Match interfaces of different classes
Separates an object’s interface from its implementation
A tree structure of simple and composite objects
Add responsibilities to objects dynamically
A single class that represents an entire subsystem
A fine-grained instance used for efficient sharing
An object representing another object

  Behavioral Patterns
A way of passing a request between a chain of objects
Encapsulate a command request as an object
A way to include language elements in a program
Sequentially access the elements of a collection
Defines simplified communication between classes
Capture and restore an object's internal state
A way of notifying change to a number of classes
Alter an object's behavior when its state changes
Encapsulates an algorithm inside a class
Defer the exact steps of an algorithm to a subclass
Defines a new operation to a class without change

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