Design patterns are essential tools in software engineering that provide well-established solutions to common problems. Selecting the right design pattern ensures efficient, maintainable, and scalable code. But how do you decide which one to use? Let’s break it down in a structured, modern approach.
Identifying the Problem Domain
Before choosing a design pattern, identify the type of problem you are solving:
🔹 Object Creation? → Use Creational Patterns
🔹 Object Assembly? → Use Structural Patterns
🔹 Object Interactions? → Use Behavioral Patterns
Creational Patterns (Managing Object Creation)
These patterns focus on the efficient creation of objects while keeping the system flexible and scalable.
| Pattern | When to Use | Simple Story | Related Patterns |
|---|---|---|---|
| Singleton | Use when only one instance of a class should exist throughout the application. | "A school has only one principal managing everything." | Factory Method, Prototype |
| Factory Method | Use when the creation process should be delegated to subclasses to maintain flexibility. | "A bakery makes different types of cakes using different recipes." | Abstract Factory, Builder |
| Abstract Factory | Use when a family of related objects needs to be created without specifying their concrete types. | "A car factory produces different models but follows the same process." | Factory Method, Prototype |
| Prototype | Use when creating objects is expensive, and cloning existing objects can improve performance. | "A painter makes exact copies of their artwork instead of repainting it." | Singleton, Builder |
| Builder | Use when constructing a complex object requires step-by-step assembly. | "Building a burger with different ingredients step by step." | Factory Method, Prototype |
Structural Patterns (Organizing Object Composition)
These patterns help structure classes and objects for flexibility and efficiency.
| Pattern | When to Use | Simple Story | Related Patterns |
|---|---|---|---|
| Adapter | Use when you need to make two incompatible interfaces work together. | "A travel adapter allows your charger to work in different countries." | Bridge, Facade |
| Bridge | Use when you want to separate abstraction from implementation for better scalability. | "A remote control works with different TV brands." | Adapter, Composite |
| Composite | Use when you need to treat a group of objects as a single entity. | "A tree consists of branches, and branches have leaves, but all are part of the tree." | Decorator, Flyweight |
| Decorator | Use when you need to add new behavior dynamically to an object. | "Adding extra cheese and toppings to a pizza without changing its base." | Composite, Proxy |
| Facade | Use when you need to simplify interactions with a complex subsystem. | "A hotel concierge handles all guest requests instead of them contacting each service separately." | Adapter, Proxy |
| Flyweight | Use when many objects share similar data, and memory optimization is crucial. | "Instead of giving each student a textbook, they all share a library copy." | Composite, Proxy |
| Proxy | Use when controlling access to an object is needed, such as for security or caching. | "A receptionist verifies visitors before letting them into an office." | Decorator, Flyweight |
Behavioral Patterns (Managing Object Interactions)
These patterns focus on how objects communicate and collaborate.
| Pattern | When to Use | Simple Story | Related Patterns |
|---|---|---|---|
| Observer | Use when multiple objects need to be notified of state changes. | "A YouTuber uploads a video, and all subscribers get notified." | Mediator, Event-driven systems |
| Strategy | Use when multiple algorithms should be interchangeable dynamically. | "A game character can switch between running, walking, and swimming modes." | State, Template Method |
| Command | Use when you need to encapsulate requests as objects for undo/redo operations. | "A TV remote records previous actions, so you can undo a channel change." | Chain of Responsibility, Mediator |
| State | Use when an object needs to change behavior dynamically based on internal state. | "A traffic light changes behavior based on the current light color." | Strategy, Observer |
| Visitor | Use when new operations need to be added to an object structure without modifying it. | "A tour guide explains different exhibits without changing the museum setup." | Composite, Iterator |
| Memento | Use when object states need to be captured and restored without exposing internal details. | "A video game lets players save and load progress at any time." | Command, State |
| Iterator | Use when sequential access is needed for a collection without exposing its structure. | "Flipping through the pages of a book one by one." | Composite, Visitor |
| Mediator | Use when complex communications between objects should be centralized. | "An air traffic controller manages communication between multiple pilots." | Observer, Chain of Responsibility |
| Chain of Responsibility | Use when a request needs to be processed by multiple handlers in sequence. | "A customer service call passes through different departments before getting solved." | Command, Mediator |
| Template Method | Use when the structure of an algorithm should be defined, but steps should be customized. | "A recipe provides basic steps, but ingredients can be changed." | Strategy, Factory Method |
Modern Approach to Choosing a Design Pattern
🔹 Scalability Concern? → Use Singleton, Factory, or Prototype to manage object creation efficiently.
🔹 Code Readability? → Use Facade or Adapter to simplify interfaces.
🔹 Extensibility? → Use Decorator or Strategy to add functionality dynamically.
🔹 Performance Optimization? → Use Flyweight or Proxy to reduce memory usage and improve speed.
🔹 Flexible Communication? → Use Observer, Mediator, or Chain of Responsibility to handle dynamic interactions.
Final Thoughts
Choosing the right design pattern depends on your specific problem and project needs. By understanding the problem domain and applying the right pattern, you can build more maintainable and scalable software. Keep experimenting with different patterns to refine your approach and create robust, efficient applications!
