Mastering GOF Design Patterns: One‑Sentence Overview of All 23 Patterns

Outline

Introduction

Design Pattern Classification

Creational Patterns

Structural Patterns

Behavioral Patterns

Article Summary

Introduction

Learning design patterns requires a solid grasp of object‑oriented fundamentals and design principles; beyond that, a holistic view of the patterns themselves is essential. This article introduces the 23 GoF patterns by classification and a one‑sentence description for each.

Design Pattern Classification

Design patterns are divided by purpose into three categories: creational, structural, and behavioral. Creational patterns (5) address object creation, structural patterns (7) describe class/object composition, and behavioral patterns (11) define algorithmic and interaction responsibilities.

According to scope, patterns are also split into class patterns (4) and object patterns (19). Class patterns handle static inheritance relationships, while object patterns manage dynamic composition.

Creational Patterns

Singleton : Guarantees a class has only one instance and provides a global access point, controlling the number of object instances.

Factory Method : Defines an interface for creating objects, allowing subclasses to decide which class to instantiate, thus delaying instantiation to subclasses.

Abstract Factory : Provides an interface for creating families of related objects without specifying concrete classes, selecting product families.

Builder : Separates the construction of a complex object from its representation, enabling the same construction process to create different representations.

Prototype : Specifies the kinds of objects to create using prototype instances and creates new objects by copying these prototypes.

Structural Patterns

Proxy : Provides a surrogate for another object to control access, essentially controlling object access.

Facade : Offers a unified high‑level interface to a set of subsystems, simplifying their usage.

Adapter : Converts one interface into another that a client expects, enabling incompatible classes to work together.

Decorator : Dynamically adds responsibilities to objects, offering more flexibility than subclassing.

Bridge : Decouples an abstraction from its implementation, allowing both to vary independently.

Flyweight : Uses sharing to support large numbers of fine‑grained objects efficiently, separating and sharing state.

Composite : Composes objects into tree structures to represent part‑whole hierarchies, treating individual and composite objects uniformly.

Behavioral Patterns

Strategy : Defines a family of algorithms, encapsulates each one, and makes them interchangeable, separating algorithm selection from implementation.

Template Method : Defines the skeleton of an algorithm in a method, deferring some steps to subclasses.

Chain of Responsibility : Gives multiple objects a chance to handle a request, forming a chain that passes the request until an object handles it, separating responsibilities dynamically.

State : Allows an object to alter its behavior when its internal state changes, effectively changing its class.

Observer : Establishes a one‑to‑many dependency so that when one object changes state, all its dependents are notified and updated.

Interpreter : Defines a representation for a language’s grammar and an interpreter that uses this representation to interpret sentences.

Command : Encapsulates a request as an object, enabling parameterization, queuing, logging, and undoable operations.

Mediator : Encapsulates how a set of objects interact, promoting loose coupling by keeping objects from referring to each other explicitly.

Iterator : Provides a way to access elements of an aggregate object sequentially without exposing its underlying representation.

Visitor : Represents an operation to be performed on elements of an object structure, allowing new operations without changing the elements.

Memento : Captures an object’s internal state without violating encapsulation, allowing the object to be restored later.

Article Summary

This article outlines the classification of design patterns, presents each of the 23 GoF patterns with concise one‑sentence explanations, and serves as a reference guide for future learning and application.