Design Patterns

Design patterns are reusable solutions to common problems encountered in software design and development. They provide a structured approach to solving design challenges and promoting best practices. Here are some commonly used design patterns:

Creational Patterns:

1. Singleton: Ensures that a class has only one instance and provides a global point of access to it.
2. Factory Method: Defines an interface for creating objects but allows subclasses to alter the type of objects that will be created.
3. Abstract Factory: Provides an interface for creating families of related or dependent objects without specifying their concrete classes.
4. Builder: Separates the construction of a complex object from its representation, allowing the same construction process to create different representations.

Structural Patterns:

1. Adapter: Allows objects with incompatible interfaces to work together by providing a wrapper that converts the interface of one class into another.
2. Decorator: Attaches additional responsibilities to an object dynamically, providing a flexible alternative to subclassing for extending functionality.
3. Facade: Provides a simplified interface to a complex system, hiding its complexity and making it easier to use.
4. Proxy: Provides a placeholder for another object to control access to it, acting as a surrogate or placeholder for the actual object.

Behavioral Patterns:

1. Observer: Defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.
2. Strategy: Defines a family of algorithms, encapsulates each one, and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it.
3. Command: Encapsulates a request as an object, thereby allowing for parameterization of clients with queues, requests, and operations.
4. Iterator: Provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation.

Architectural Patterns:

1. Model-View-Controller (MVC): Separates the presentation layer (view), business logic (controller), and data (model) to achieve separation of concerns and modularity.
2. Repository Pattern: Mediates between the domain and data mapping layers, acting as a collection of domain objects that acts like a collection of data.
3. Dependency Injection: Inverts the control of creating and managing dependencies, allowing components to be loosely coupled and easily replaced.
4. Event-Driven Architecture (EDA): Decouples components by allowing them to communicate through events, promoting loose coupling and scalability.

These design patterns help software developers create maintainable, scalable, and flexible software systems by providing well-established solutions to recurring design problems. Understanding and applying design patterns appropriately can lead to improved code quality, easier maintenance, and better software architecture.