Advanced Design Patterns

Introduction

Design patterns are reusable solutions to common problems that occur in software design. They represent the best practices used by experienced object-oriented software developers.

Creational Design Patterns

Creational patterns provide a way to create objects while hiding the creation logic, rather than instantiating objects directly using a constructor. This gives the program more flexibility in deciding which objects need to be created for a given use case.

Singleton Pattern

The Singleton Pattern ensures that a class has only one instance and provides a global point of access to it. For example, a database connection is a good candidate for Singleton, as it needs to be controlled because it can have a heavy memory footprint.

Factory Pattern

The Factory Pattern provides a way to encapsulate a group of individual factories that have a common theme without specifying their concrete classes. For example, a car factory can produce different types of cars.

Abstract Factory Pattern

The Abstract Factory Pattern provides a way to encapsulate a group of individual factories that have a common theme without specifying their concrete classes.

Structural Design Patterns

Structural patterns explain how to assemble objects and classes into larger structures while keeping these structures flexible and efficient.

Adapter Pattern

The Adapter Pattern works as a bridge between two incompatible interfaces. This pattern involves a single class, which is responsible to join functionalities of independent or incompatible interfaces.

Decorator Pattern

The Decorator Pattern allows a user to add new functionality to an existing object without altering its structure.

Composite Pattern

The Composite Pattern is used where we need to treat a group of objects in a similar way as a single object.

Behavioral Design Patterns

Behavioral patterns provide a way to define the communication between objects in your system.

Observer Pattern

The Observer Pattern is used when there is one-to-many relationship between objects such as if one object is modified, its dependent objects are to be notified automatically.

Strategy Pattern

The Strategy Pattern is used when we have multiple algorithms for a specific task and the client decides the actual implementation to be used at runtime.

Command Pattern

The Command Pattern is used to implement loose coupling in a request-response model.

Conclusion

Design patterns are a very important tool for every developer. They provide a general solution, documented in a format that doesn't require specifics tied to a particular problem.

Summary

Design patterns are reusable solutions to common problems in software design. They are divided into three types: Creational, Structural, and Behavioral. Creational patterns provide ways to create objects, Structural patterns explain how to assemble objects and classes into larger structures, and Behavioral patterns define the communication between objects.

Analogy

Design patterns are like blueprints for a house. They provide a general design solution for a particular problem, just like a blueprint provides a design for a house. But just like a blueprint, you can't just take a design pattern and transform it into a beautifully constructed house without a team of professionals. Similarly, design patterns are not finished designs that can be transformed directly into code; they are descriptions or templates for how to solve a problem that can be used in many different situations.