Introduction to Gang of Four (GoF) Design Patterns

Design patterns gained popularity in computer science after the book Design Patterns: Elements of Reusable Object-Oriented Software was published in 1994 by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides; and together they are called the "Gang of Four" or "GoF".

The 23 GOF design patterns can be broadly classified into the following three categories:

• Creational patterns

  • These are patterns related to object creation. 

  • There are 5 creational patterns mentioned in the GoF book:

    1. Factory method

    2. Abstract Factory

    3. Builder

    4. Prototype

    5. Singleton 

• Structural patterns

  • These are related to organizing classes and objects to form a bigger structure, to provide clarity and increase maintainability.

  • There are 7 structural design patterns mentioned in the GoF book:

    1. Adapter

    2. Bridge

    3. Proxy

    4. Decorator

    5. Composite

    6. Facade

    7. Flyweight

• Behavioral patterns

  • These are related to the communication and control the flow between the objects.

  • There are 11 behavioral design patterns mentioned in the GoF book:

    1. Chain of Responsibility

    2. Observer

    3. Strategy

    4. Template

    5. State

    6. Visitor

    7. Iterator

    8. Command

    9. Interpreter

    10. Mediator

    11. Memento

There are also other design patterns discovered and documented later, but the GoF remains the most popular.