Essential Design Patterns in Software Engineering to Know for Design Strategy and Software I

Understanding essential design patterns in software engineering helps create efficient, maintainable code. These patterns, like Singleton and Factory Method, guide developers in structuring their applications, enhancing flexibility, and promoting best practices in design strategy.

1. Singleton Pattern

   • Ensures a class has only one instance and provides a global point of access to it.
   • Useful for managing shared resources, such as configuration settings or connection pools.
   • Prevents multiple instantiations, which can lead to inconsistent states.

2. Factory Method Pattern

   • Defines an interface for creating an object but allows subclasses to alter the type of objects that will be created.
   • Promotes loose coupling by eliminating the need to specify the exact class of the object being created.
   • Useful for managing and encapsulating the instantiation process.

3. Abstract Factory Pattern

   • Provides an interface for creating families of related or dependent objects without specifying their concrete classes.
   • Facilitates the creation of products that belong to a particular theme or context.
   • Enhances flexibility and scalability by allowing easy addition of new product families.

4. Builder Pattern

   • Separates the construction of a complex object from its representation, allowing the same construction process to create different representations.
   • Useful for creating objects with many optional parameters or configurations.
   • Promotes code readability and maintainability by using a step-by-step approach.

5. Prototype Pattern

   • Allows creating new objects by copying an existing object, known as the prototype.
   • Useful for performance optimization when object creation is costly.
   • Supports dynamic object creation and can simplify the instantiation of complex objects.

6. Adapter Pattern

   • Allows incompatible interfaces to work together by converting the interface of a class into another interface that clients expect.
   • Promotes reusability by enabling existing classes to be used in new contexts without modification.
   • Useful for integrating legacy code with new systems.

7. Decorator Pattern

   • Adds new functionality to an object dynamically without altering its structure.
   • Provides a flexible alternative to subclassing for extending behavior.
   • Useful for adhering to the Single Responsibility Principle by allowing behavior to be divided among multiple decorators.

8. Observer Pattern

   • Defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.
   • Promotes loose coupling between the subject and observers.
   • Useful for implementing event-driven systems and maintaining consistency across multiple components.

9. Strategy Pattern

   • Defines a family of algorithms, encapsulates each one, and makes them interchangeable.
   • Allows the algorithm to vary independently from clients that use it.
   • Promotes flexibility and reusability by enabling the selection of algorithms at runtime.

10. Command Pattern

    • Encapsulates a request as an object, thereby allowing for parameterization of clients with queues, requests, and operations.
    • Supports undoable operations and transaction management.
    • Promotes decoupling between the sender and receiver of a request.

11. Composite Pattern

    • Composes objects into tree structures to represent part-whole hierarchies.
    • Allows clients to treat individual objects and compositions uniformly.
    • Simplifies client code by allowing it to work with complex tree structures without needing to differentiate between leaf and composite nodes.

12. Facade Pattern

    • Provides a simplified interface to a complex subsystem, making it easier to use.
    • Reduces dependencies on the subsystem, promoting loose coupling.
    • Useful for improving code readability and reducing the learning curve for new developers.

13. Proxy Pattern

    • Provides a surrogate or placeholder for another object to control access to it.
    • Useful for implementing lazy initialization, access control, logging, and caching.
    • Promotes separation of concerns by allowing additional functionality to be added without modifying the original object.

14. Iterator Pattern

    • Provides a way to access the elements of a collection sequentially without exposing its underlying representation.
    • Promotes encapsulation and allows for different traversal methods.
    • Useful for supporting multiple iterations over a collection without needing to modify the collection itself.

15. State Pattern

    • Allows an object to alter its behavior when its internal state changes, appearing to change its class.
    • Promotes cleaner code by encapsulating state-specific behavior in separate classes.
    • Useful for managing complex state transitions and reducing conditional logic in code.