Design Pattern

Design patterns ¹ are proven or reusable solutions to common software design problems. They provide structured approaches to organizing code, improving reusability, flexibility, and maintainability. Think of them as a blueprint or template that guides developers in solving recurring issues in software development.

Three main types of design pattern

• Creational Patterns – Focus on how objects are created, making it easier to manage object creation and avoid unnecessary complexity.
• Structural Patterns – Help organize and connect different parts of a system, ensuring they work together efficiently.
• Behavioral Patterns – Define how objects interact and communicate, making the system more flexible and easier to extend.

In Depth

Creational Patterns

“How objects are created”

1. Singleton

   • Ensures only one instance of a class exists and provides a way to access it globally.
   • Useful for managing configurations or logging.

2. Factory Method

   • Provides a flexible way to create objects without specifying their exact class.
   • Useful when dealing with multiple related object types.

3. Builder

   • Helps create complex objects step by step.
   • Useful when an object has many optional parts.

Structural Patterns

“How objects are organized”

1. Adapter
   • Allows two incompatible interfaces to work together.
   • e.g., Like a power plug adapter that makes a foreign device work in a local socket.
2. Composite
   • Lets you treat a group of objects the same way as a single object.
   • e.g., Useful for representing tree structures like UI components.
3. Decorator
   • Adds new functionality to an object without modifying its original structure.
   • e.g., Like adding extra features to a car without redesigning it.

Behavioral Patterns

How objects communicate

1. Observer
   • Allows multiple objects to react when one object changes.
   • e.g., Like a notification system where many users receive updates.
2. Strategy
   • Lets you switch between different algorithms without changing the main code.
   • e.g., Like choosing different payment methods in an online store.
3. Command
   • Encapsulates a request as an object, making it easy to queue, log, or undo actions.
   • e.g., Like storing a list of actions in a video game to allow undo/redo.

---

🔗 Sources

Footnotes

1. Difference Between Design Patterns and Design Principles ↩