Design Patterns

Design Patterns


Object-oriented programming (OOP) has revolutionized software development, providing a structured and modular approach to creating complex applications.

Within OOP, design patterns are blueprints for solving everyday problems and achieving well-structured, maintainable code.

These patterns provide reusable solutions for typical design problems, promoting code reusability, flexibility, and maintainability.

Types of Object-Oriented Design Patterns

Object-oriented design patterns can be categorized into three main types:

  • Creational Patterns: These patterns focus on object creation, providing mechanisms for creating objects in a controlled and flexible manner.
  • Structural Patterns: These patterns concern organising and arranging classes and objects, ensuring cohesion and loose coupling.
  • Behavioural Patterns: These patterns deal with communication and interaction between objects, defining how objects should collaborate and coordinate their actions.

List of Object-Oriented Design Patterns

Here’s a comprehensive list of object-oriented design patterns, along with a brief explanation for each pattern:

  1. Creational Patterns:
    • Factory Method: Provides an interface for creating families of related objects without specifying their concrete classes. (Link)
    • Abstract Factory: Defines a family of interrelated or dependent factories. (Link)
    • Builder: Separates object construction from its representation.
    • Prototype: Provides a way to copy existing objects without violating encapsulation. (Link)
    • Singleton: Ensures a class has only one instance, providing a global access point to that instance. (Link)
    • Object Pool: Provides a pool of reusable objects. (Link)
  2. Structural Patterns:
    • Adapter: Allows objects with incompatible interfaces to collaborate. (Link)
    • Bridge: Decouples an abstraction from its implementation, allowing for independent variations. (Link)
    • Composite: Creates a hierarchical tree of objects with the same interface, treating individual objects and compositions uniformly. (Link)
    • Decorator: Attaches additional responsibilities to objects dynamically. (Link)
    • Facade: Provides a simplified interface to a complex system. (Link)
    • Flyweight: Uses sharing to support a large number of similar objects efficiently. (Link)
    • Proxy: Provides a surrogate or placeholder for another object to control access, provide additional functionality, or protect the real object. (Link)
    • Null Object: Provides a tool for handling null values safely and predictably. (Link)

  3. Behavioural Patterns:
    • Chain of Responsibility: Delegates a request to a chain of objects, traversing the chain until one object handles the request. (Link)
    • Command: Encapsulates a request as an object, allowing for greater flexibility in handling requests. (Link)
    • Interpreter: Defines a language and provides an interpreter to execute the language’s expressions. (Link)
    • Iterator: Sequentially accesses the elements of an aggregate object. (Link)
    • Mediator: Defines simplified communication between objects, reducing coupling and improving modularity. (Link)
    • Memento: Captures the state of an object at a specific point in time, allowing for its restoration later. (Link)
    • Observer: Defines a one-to-many dependency between objects, allowing them to be notified of changes in state. (Link)
    • State: Allows an object to alter its behaviour when its internal state changes. (Link)
    • Strategy: Defines a family of algorithms, allowing objects to switch between them dynamically. (Link)
    • Template Method: Defines the skeleton of an algorithm, allowing subclasses to override specific steps. (Link)
    • Visitor: Defines a new operation to be applied to the elements of an object structure. (Link)


Object-oriented design patterns serve as essential tools for software development, providing reusable solutions to common problems and promoting code reusability, flexibility, and maintainability.

Developers can create more robust, scalable, and adaptable applications by understanding and applying these patterns.


Hi, my name is Stephen Finchett. I have been a software engineer for over 30 years and worked on complex, business critical, multi-user systems for all of my career. For the last 15 years, I have been concentrating on web based solutions using the Microsoft Stack including ASP.Net, C#, TypeScript, SQL Server and running everything at scale within Kubernetes.