Design Patterns

What is a Design Pattern?

Design Pattern is a re-usable, high quality solution to a given requirement, task or recurring problem. Further, it does not comprise of a complete solution that may be instantly converted to a code component, rather it provides a framework for how to solve a problem.

In 1994, the release of the book Design Patterns, Elements of Reusable Object Oriented Software made design patterns popular.

Because design patterns consist of proven reusable architectural concepts, they are reliable and they speed up software development process.

Design Patterns are in a continuous phase of evolution, which means that they keep on getting better & better as they are tested against time, reliability and subjected to continuous improvements. Further, design patterns have evolved towards targeting specific domains. For example, windows-based banking applications are usually based on singleton patterns, e-commerce web applications are based on the MVC (Model-View-Controller) pattern.

Design Patterns are categorized into 3 types:

1) Creational Patterns

The Creational Design Patterns focus on how objects are created and utilized in an application. They tackle the aspects of when and how objects are created, keeping in mind what is the best way these objects should be created.

Listed below are some of the commonly known Creational Design Patterns:
>>> Abstract Factory Pattern
>>> Factory Pattern
>>> Builder Pattern
>>> Lazy Pattern
>>> Prototype Pattern
>>> Singleton Pattern

2) Structural Patterns

A structural design pattern establishes a relationship between entities. Thus making it easier for different components of an application to interact with each other. Following are some of the commonly known structural patterns:
>>> Adapter Pattern
>>> Bridge Pattern
>>> Composite Pattern
>>> Decorator Pattern
>>> Facade Pattern
>>> Flyweight Pattern
>>> Proxy Pattern

3) Behavioral Patterns

Behaviorial design patterns focus on improving the communication between different objects. Following are different types of behavioral patterns:
>>> Chain Or Responsibilities Pattern
>>> Command Pattern
>>> Observer Pattern