This article is presented by:
Sapana Mehta


Design Patterns


A pattern is a proven solution to a problem in a context.
Christopher Alexander says each pattern is a three-part rule which expresses a relation between a certain context, a problem, and a solution.
Design patterns represent a solutions to problems that arise when developing software within a particular context.
i.e Patterns = problems.solution pairs in a context

Background

Started in 1987 by Ward Cunningham and Ken Beck who were working with Smalltalk and designing GUIs.
Popularized by Gamma, Helm, Johnson and Vlissides (The gang of four, Go4)
The three of Go4 were working on frameworks (E++,Unidraw, HotDraw)
Design pattern use a consistent documentation approach
Design pattern are granular and applied at different levels such as frameworks, subsystems and sub-subsystems
Design patterns are often organized as creational, structural or behavioral


Categorizing Pattern

Patterns, then, represent expert solutions to
recurring problems in a context and thus have
been captured at many levels of abstraction
and in numerous domains. Numerous
categories are:
Design
Architectural
Analysis
Creational
Structural
Behavioral

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