What's the best design pattern for your system?

1 Factor 1: System complexity

One of the first things to consider is how complex your system is, and how likely it is to change in the future. Complex systems often have many components that interact with each other, and may require different levels of abstraction, modularity, and scalability. Design patterns can help you manage this complexity by defining clear roles and responsibilities for each component, and by decoupling them from each other. For example, the MVC (Model-View-Controller) pattern separates the data, the logic, and the presentation of your system, making it easier to test, modify, and reuse each part.

2 Factor 2: System performance

Another factor to consider is how performance-sensitive your system is, and what trade-offs you are willing to make between speed, memory, and reliability. Design patterns can help you optimize your system performance by reducing unnecessary computations, avoiding duplication, and caching results. For example, the Singleton pattern ensures that only one instance of a class is created and shared throughout your system, saving memory and ensuring consistency. The Flyweight pattern reduces the number of objects by sharing common attributes and behaviors among them, saving memory and improving speed.

3 Factor 3: System functionality

A third factor to consider is what functionality your system needs to provide, and how flexible and extensible it should be. Design patterns can help you implement specific features and behaviors in your system, and allow you to modify or extend them without breaking existing code. For example, the Strategy pattern lets you define a family of algorithms that can be interchanged at runtime, giving you more options and control over your system behavior. The Decorator pattern lets you add new functionality to an existing object without changing its interface, giving you more flexibility and compatibility.

4 Factor 4: System design principles

A fourth factor to consider is what design principles you want to follow in your system, and how they align with the design patterns you choose. Design principles are general guidelines that help you write better code, such as the SOLID principles (Single responsibility, Open-closed, Liskov substitution, Interface segregation, and Dependency inversion). Design patterns can help you adhere to these principles by enforcing good practices, such as high cohesion, low coupling, abstraction, encapsulation, and polymorphism. For example, the Observer pattern follows the Open-closed principle by allowing an object to notify other objects about its state changes, without requiring them to know about each other.

5 Factor 5: System context

A fifth factor to consider is the context in which your system operates, and how it affects your design choices. The context includes the requirements, constraints, and expectations of your system's users, stakeholders, and environment. Design patterns can help you adapt your system to different contexts by providing solutions that are proven, tested, and widely used in similar situations. For example, the Factory method pattern is useful when you need to create objects without specifying their exact classes, allowing you to defer the decision to a subclass or a parameter. The Adapter pattern is useful when you need to make incompatible interfaces work together, allowing you to wrap one object with another that matches the expected interface.

6 Factor 6: System preferences

A sixth and final factor to consider is your personal or team preferences, and how they influence your design style and approach. Preferences include your experience, skills, goals, and preferences for certain languages, tools, or frameworks. Design patterns can help you express your preferences by providing a common vocabulary, a consistent structure, and a shared understanding of your system. For example, if you prefer a functional programming style, you may use the Command pattern to encapsulate actions as objects that can be passed, stored, or executed. If you prefer a reactive programming style, you may use the Reactive Streams pattern to create asynchronous data streams that can be observed, transformed, and composed.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?