Here are some of the most common design patterns in software development today:
1. Singleton Pattern
- Purpose: Ensures a class has only one instance and provides a global point of access to it.
- Use Cases: Used in configurations, logging, database connections, etc.
- Why Popular: Helps in managing shared resources efficiently.
2. Factory Method Pattern
- Purpose: Defines an interface for creating objects but lets subclasses alter the type of objects that will be created.
- Use Cases: When a class can’t anticipate the type of objects it needs to create or when objects need to be created with varying configurations.
- Why Popular: Promotes loose coupling and scalability.
3. Observer Pattern
- Purpose: Allows an object (the subject) to notify other objects (observers) about changes in its state.
- Use Cases: Event handling systems, real-time messaging, data binding in user interfaces.
- Why Popular: Facilitates the implementation of event-driven systems.
4. Decorator Pattern
- Purpose: Attaches additional responsibilities to an object dynamically. Provides a flexible alternative to subclassing for extending functionality.
- Use Cases: Used for adding features or behaviors at runtime without altering the object structure.
- Why Popular: Supports Open/Closed Principle by allowing enhancements without modifying existing code.
5. Strategy Pattern
- Purpose: Defines a family of algorithms, encapsulates each one, and makes them interchangeable.
- Use Cases: Used when you have multiple ways of doing something, like sorting or validating data.
- Why Popular: Enhances flexibility by allowing algorithms to be selected at runtime.
6. Command Pattern
- Purpose: Encapsulates a request as an object, thereby allowing for parameterization of clients with different requests.
- Use Cases: Undo/redo operations, queuing tasks, and logging changes.
- Why Popular: Decouples sender and receiver, making the system more modular and extensible.
7. Builder Pattern
- Purpose: Separates the construction of a complex object from its representation, allowing the same construction process to create different representations.
- Use Cases: When creating objects with many optional parameters.
- Why Popular: Simplifies object creation and enhances code readability.
8. Adapter Pattern
- Purpose: Converts an interface of a class into another interface clients expect. Allows incompatible interfaces to work together.
- Use Cases: Integrating with third-party code or legacy systems.
- Why Popular: Increases compatibility between different components or libraries.
9. Microservices Pattern
- Purpose: Structures an application as a collection of loosely coupled services.
- Use Cases: Highly scalable, independently deployable services in cloud-native applications.
- Why Popular: Enables continuous delivery, scalability, and easier management of complex applications.
10. Event Sourcing Pattern
- Purpose: Stores the state of a system as a sequence of state-changing events.
- Use Cases: Financial systems, logging systems, and applications where maintaining a full history of state changes is crucial.
- Why Popular: Provides a complete audit trail and allows easy recovery and replay of states.
11. CQRS (Command Query Responsibility Segregation) Pattern
- Purpose: Segregates read and write operations to optimize performance, scalability, and security.
- Use Cases: Systems with heavy read or write operations where the data model differs for reads and writes.
- Why Popular: Improves scalability, performance, and simplifies complex data flows.
12. API Gateway Pattern
- Purpose: Provides a single entry point for a group of microservices, handling cross-cutting concerns like security, monitoring, and rate limiting.
- Use Cases: Microservices architecture, serverless computing.
- Why Popular: Simplifies client interaction with microservices and centralizes concerns.
13. Mediator Pattern
- Purpose: Defines an object that encapsulates how a set of objects interact. Promotes loose coupling by keeping objects from referring to each other explicitly.
- Use Cases: Chat systems, complex workflows, UI components that need to communicate.
- Why Popular: Reduces dependencies between communicating objects.
14. Chain of Responsibility Pattern
- Purpose: Passes a request along a chain of handlers, allowing each handler to either handle the request or pass it to the next handler.
- Use Cases: Event processing pipelines, middleware stacks, authorization checks.
- Why Popular: Enhances flexibility in assigning responsibilities and handling requests dynamically.
15. Proxy Pattern
- Purpose: Provides a surrogate or placeholder for another object to control access to it.
- Use Cases: Caching, lazy initialization, and access control.
- Why Popular: Enhances performance, security, and control over resource access.
These patterns address various design concerns such as scalability, flexibility, maintainability, and reusability, making them integral to modern software development practices.