Overview of Common Design Patterns in Software Development

Introduction to Design Patterns

Design patterns are standard solutions to common problems in software design. Each pattern represents a best practice used by experienced object-oriented software developers. Design patterns are about designing and solving problems using principles such as reusability, scalability, and maintainability.

Creational Patterns

Singleton

• Summary: Use a Singleton to ensure that a class has only one instance, and provide a global point of access to this instance. It’s ideal for managing shared resources.

Factory Method

• Summary: Implement a Factory Method to create objects without specifying the exact class of object that will be created. This promotes loose coupling and scalability.

Builder

• Summary: Apply the Builder pattern to construct complex objects step-by-step, and allow the process to create different types and representations of an object.

Prototype

• Summary: Use the Prototype pattern to avoid the overhead of initializing objects standardly and instead create them by copying a pre-initialized prototype.

Abstract Factory

• Summary: Utilize an Abstract Factory when you need to create families of related or dependent objects without specifying their concrete classes.

Structural Patterns

Adapter

• Summary: Use an Adapter to allow otherwise incompatible interfaces to work together by wrapping their differences in an adapter class.

Facade

• Summary: Employ a Facade to provide a simple, easy to understand user interface over a large and complex body of code.

Decorator

• Summary: Use a Decorator to add new functionality to an object dynamically, without altering its structure.

Composite

• Summary: Implement a Composite to treat individual objects and compositions of objects uniformly.

Bridge

• Summary: Apply the Bridge pattern to decouple an abstraction from its implementation so that the two can vary independently.

Proxy

• Summary: Use a Proxy to provide a placeholder for another object to control access, reduce cost, and reduce complexity.

Behavioral Patterns

Strategy

• Summary: Use a Strategy to define a family of algorithms, encapsulate each one, and make them interchangeable.

Observer

• Summary: Implement an Observer to allow a subscription mechanism to notify multiple objects about any events that happen to the object they’re observing.

Command

• Summary: Apply the Command pattern to turn requests or simple operations into objects which can be parameterized and queued.

Iterator

• Summary: Use an Iterator to provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.

Template Method

• Summary: Utilize the Template Method to define the skeleton of an algorithm, deferring some steps to subclasses while maintaining the structure.

Mediator

• Summary: Employ a Mediator to reduce direct communications between objects and allow them to communicate independently.

Memento

• Summary: Use the Memento pattern to capture and externalize an object’s internal state so that it can be restored later without violating encapsulation.

State

• Summary: Apply the State pattern to allow an object to alter its behavior when its internal state changes, appearing as if it changed its class.

Visitor

• Summary: Use a Visitor to perform operations on elements of an object structure without changing the classes on which it operates.

Conclusion

Understanding these design patterns is crucial for solving specific design problems and ensuring that a system is scalable, maintainable, and decoupled. Each pattern provides a roadmap for tackling common challenges that arise during software development.