Design Patterns
I often find myself talking with developers (some of whom call themselves Senior) who say they don’t know Design Patterns or don’t think they’re useful. I’d like to share a few thoughts on the subject.
To some, they may look like nothing more than abstract theory with no practical application. But let me explain why Design Patterns can be genuinely useful and make a real difference in your day-to-day work.
Why use Design Patterns
Design patterns in programming are recurring solutions to common problems that come up in software development.
Imagine walking into your kitchen: you want to cook a delicious dinner. But instead of following a recipe, you start improvising, trying to remember everything you’ve read in cookbooks. The result? You might end up with a mess. Now, what if you had a set of ready-made recipes, just waiting to be followed? Well, that’s exactly what Design Patterns do in the world of programming. Design Patterns are essentially “recipes” for solving common problems in software.
Ignoring Design Patterns means giving up powerful tools that can significantly improve the quality of our work. So I encourage you to explore them and to treat them as an integral part of your professional growth, because not only will they help you become a better developer, they’ll also improve the quality of your team’s work.
Benefits
- Proven solutions: Design Patterns offer proven solutions to common problems. When we face programming challenges, we don’t always have to reinvent the wheel. These “recipes” let us tackle common situations with tried-and-tested strategies.
- Code maintainability: Using Design Patterns makes code more readable and maintainable. This is crucial in a collaborative work environment. When your code is clear and follows recognized patterns, it’s easier for your colleagues to understand it, change it and fix any bugs.
- Effective communication: Design Patterns provide a common language among developers. When we say “Observer” or “Factory”, we all know what we’re talking about. This simplifies communication and reduces the risk of misunderstandings when working as a team.
- Adaptability and scalability: In a fast-moving field like software development, Design Patterns help us build systems that are more adaptable and scalable. If the project changes, these patterns let us make modifications without having to rewrite the code from scratch.
- Professional growth: Understanding Design Patterns is a sign of maturity as a developer. It shows that you’ve invested in your learning and that you’re ready to take on more complex challenges. This can open many doors in your career.
The main Design Patterns
There are about 23 main Design Patterns, as listed in the book “Design Patterns: Elements of Reusable Object-Oriented Software” by Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides, known as the “Gang of Four” (GoF), and they are divided into three main categories: Creational, Structural and Behavioral. I stress about because there are actually other patterns and variants developed over time that don’t necessarily fit into these categories, which could push the overall number much higher, depending on the community and the context.
Here is a list of the main patterns, grouped by category and with a short description. Click on a pattern’s name to see a more detailed description with code examples and use cases.
Creational Patterns
They deal with object creation, giving you more control over how objects are instantiated.
- Singleton: Ensures that a class has only one instance and provides a global point of access to it.
- Factory Method: Defines an interface for creating objects, but lets subclasses decide which class to instantiate.
- Abstract Factory: Provides an interface for creating families of related objects without specifying their concrete classes.
- Builder: Separates the construction of a complex object from its representation, allowing objects to be created step by step.
- Prototype: Lets you clone existing objects instead of creating them from scratch.
Structural Patterns
They deal with composing classes or objects to form larger structures.
- Adapter: Allows incompatible interfaces to work together, acting as a bridge between two classes.
- Bridge: Decouples an abstraction from its implementation, so that the two can vary independently.
- Composite: Lets you treat individual objects and compositions of objects uniformly (hierarchical tree).
- Decorator: Dynamically adds behavior to an object without modifying the code of the original class.
- Facade: Provides a simple, unified interface to a set of interfaces in a subsystem.
- Flyweight: Reduces the number of objects created, minimizing memory usage for similar objects.
- Proxy: Provides a surrogate or placeholder to control access to an object.
Behavioral Patterns
These patterns deal with the interactions and responsibilities between objects
- Chain of Responsibility: Gives multiple objects the chance to handle a request by passing it along a chain.
- Command: Encapsulates a request as an object, letting you parameterize methods with requests, queues and undoable operations.
- Interpreter: Provides a way to evaluate sentences in a language.
- Iterator: Provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
- Mediator: Defines an object that encapsulates how a set of objects interact, reducing the direct dependencies between them.
- Memento: Lets you capture and restore an object’s internal state without violating its encapsulation.
- Observer: Defines a one-to-many dependency between objects, so that when one object changes state, all its dependents are notified and updated automatically.
- State: Allows an object to change its behavior when its internal state changes.
- Strategy: Defines a family of algorithms, encapsulates each one separately and makes them interchangeable.
- Template Method: Defines the skeleton of an algorithm in a method, deferring some steps to subclasses.
- Visitor: Lets you define new operations on objects without changing their classes.