The Language of Design Patterns

I'm not fond of the meme "design patterns are missing language features". Yes, some design patterns (looking at you, Strategy pattern) are obsoleted by simple things like first-class functions. And yes, you can theoretically turn most patterns into language builtins. But language design is the art of the holistic. Every feature needs to work well with every other feature. Adding an "observer" feature makes every *future* feature that much harder to implement. So sure, "design patterns are missing language features", but that's a necessary tradeoff. The language provides a base set of features that work well together. If you repeatedly combine them in a certain way to solve a certain class of problem, then you have a pattern. Even if the language has powerful features that eliminate certain known design patterns, you still have patterns. They're just more complex patterns than you'd get otherwise, since you have stronger primitives. You don't get transformer stacks in C. «But some languages like lisp let you add new features!» Most of those communities discourage extending the language unless you absolutely need to. In other words, you can *replace* the design pattern with a new language feature, but you probably *shouldn't*. (This is because features created through macros and metaprogramming behave unpredictably when used with other language features. Language design is the art of the holistic.) So the use of a design pattern COULD mean a useful language feature is missing. But it COULD ALSO mean that a potential language feature was deemed unnecessary, and including it would do more harm than good.

𝗦𝗼𝗳𝘁𝘄𝗮𝗿𝗲 𝗔𝗿𝗰𝗵𝗶𝘁𝗲𝗰𝘁𝘂𝗿𝗲 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀: 𝗠𝗩𝗖, 𝗠𝗩𝗣, 𝗠𝗩𝗜, 𝗠𝗩𝗩𝗠, 𝗩𝗜𝗣𝗘𝗥 Design patterns are essential tools for any developer, offering a framework for structuring code in a clean, maintainable, and scalable way. Today, we'll delve into five of the most popular design patterns, exploring their strengths and weaknesses to help you choose the right fit for your next project. 𝗠𝗩𝗖 (𝗠𝗼𝗱𝗲𝗹-𝗩𝗶𝗲𝘄-𝗖𝗼𝗻𝘁𝗿𝗼𝗹𝗹𝗲𝗿): - Classic pattern separating code into three layers:     - 𝗠𝗼𝗱𝗲𝗹: Data and business logic     - 𝗩𝗶𝗲𝘄: Presentation of data to the user     - 𝗖𝗼𝗻𝘁𝗿𝗼𝗹𝗹𝗲𝗿: Handles user input and updates model/view - Simple and familiar, but can lead to tightly coupled components in complex applications. 𝗠𝗩𝗣 (𝗠𝗼𝗱𝗲𝗹-𝗩𝗶𝗲𝘄-𝗣𝗿𝗲𝘀𝗲𝗻𝘁𝗲𝗿): - Introduces a Presenter to mediate between view and model. - Improves separation of concerns and testability. - Requires additional boilerplate code compared to MVC. 𝗠𝗩𝗜 (𝗠𝗼𝗱𝗲𝗹-𝗩𝗶𝗲𝘄-𝗜𝗻𝘁𝗲𝗻𝘁): - Built for reactive programming. - View emits intents, handled by the model, updating state and view. - Promotes unidirectional data flow and simplifies UI logic. - May require a steeper learning curve. 𝗠𝗩𝗩𝗠 (𝗠𝗼𝗱𝗲𝗹-𝗩𝗶𝗲𝘄-𝗩𝗶𝗲𝘄𝗠𝗼𝗱𝗲𝗹): - View binds to a ViewModel holding data and display logic. - ViewModel updates by the model, then updates the view. - Well-suited for reactive frameworks and complex UIs. - Requires additional ViewModel setup compared to MVP. 𝗩𝗜𝗣𝗘𝗥 (𝗩𝗶𝗲𝘄, 𝗜𝗻𝘁𝗲𝗿𝗮𝗰𝘁𝗼𝗿, 𝗣𝗿𝗲𝘀𝗲𝗻𝘁𝗲𝗿, 𝗘𝗻𝘁𝗶𝘁𝘆, 𝗥𝗼𝘂𝘁𝗲𝗿): - Designed for large and complex applications. - Five layers: View, Interactor (business logic), Presenter (data preparation), Entity (data models), Router (data flow coordination). - Enhances modularity and maintainability for massive projects. - Requires meticulous planning and understanding due to its complexity. 𝗖𝗵𝗼𝗼𝘀𝗶𝗻𝗴 𝘁𝗵𝗲 𝗥𝗶𝗴𝗵𝘁 𝗣𝗮𝘁𝘁𝗲𝗿𝗻: The optimal pattern depends on various factors, including: - 𝗣𝗿𝗼𝗷𝗲𝗰𝘁 𝘀𝗶𝘇𝗲 𝗮𝗻𝗱 𝗰𝗼𝗺𝗽𝗹𝗲𝘅𝗶𝘁𝘆: MVC/MVP for simple apps, MVI/MVVM for reactive apps, VIPER for large projects. - 𝗧𝗲𝗮𝗺 𝗲𝘅𝗽𝗲𝗿𝗶𝗲𝗻𝗰𝗲: Choose a pattern familiar to your team to avoid learning curves. - 𝗣𝗲𝗿𝘀𝗼𝗻𝗮𝗹 𝗽𝗿𝗲𝗳𝗲𝗿𝗲𝗻𝗰𝗲: Experiment and find what works best for you and your team. Ultimately, experimenting and finding what works best for you and your team is key. What do you think? Which software architecture pattern is your favorite?

Clean code is nice. But scalable architecture? That’s what makes you irreplaceable. Early in my journey, I thought “writing clean code” was enough… Until systems scaled. Teams grew. Bugs multiplied. That’s when I discovered Design Patterns, and things started making sense. Here’s a simple breakdown that can save you hundreds of hours of confusion. 🔷 Creational Patterns: Master Object Creation These patterns handle how objects are created. Perfect when you want flexibility, reusability, and less tight coupling. 💡 Use these when: You want only one instance (Singleton) You need blueprints to build complex objects step-by-step (Builder) You want to switch object types at runtime (Factory, Abstract Factory) You want to duplicate existing objects efficiently (Prototype) 🔷 Structural Patterns: Organise the Chaos Think of this as the architecture layer. These patterns help you compose and structure code efficiently. 💡 Use these when: You’re bridging mismatched interfaces (Adapter) You want to wrap and enhance existing objects (Decorator) You need to simplify a complex system into one entry point (Facade) You’re building object trees (Composite) You want memory optimization (Flyweight) You want to control access and protection (Proxy, Bridge) 🔷 Behavioural Patterns: Handle Interactions & Responsibilities These deal with how objects interact and share responsibilities. It’s about communication, delegation, and dynamic behavior. 💡 Use these when: You want to notify multiple observers of changes (Observer) You’re navigating through collections (Iterator) You want to encapsulate operations or algorithms (Command, Strategy) You need undo/redo functionality (Memento) You need to manage state transitions (State) You’re passing tasks down a chain (Chain of Responsibility) 📌 Whether you're preparing for interviews or trying to scale your application, understanding these 3 categories is a must: 🔹 Creational → Creating Objects 🔹 Structural → Assembling Objects 🔹 Behavioral → Object Interaction & Responsibilities Mastering these gives you a mental map to write scalable, reusable, and testable code. It’s not about memorising them, it's about knowing when and why to use them. #softwareengineering #systemdesign #linkedintech #sde #connections #networking LinkedIn LinkedIn News 

𝗛𝗼𝘄 𝘁𝗼 𝘀𝗲𝗹𝗲𝗰𝘁 𝗗𝗲𝘀𝗶𝗴𝗻 𝗣𝗮𝘁𝘁𝗲𝗿𝗻? Choosing the correct design pattern in software engineering is critical to practical problem-solving. This guide simplifies the process, helping you decide between patterns based on specific needs. It offers concise descriptions and valuable use cases for each pattern, making understanding and applying them in real-world scenarios easier. To select a pattern, we must first go through the problem identification. If the problem is related to:  🔸 Object Creation? → Creational Patterns  🔸 Object Assembly? → Structural Patterns  🔸 Object Interactions? → Behavioral Patterns So, let's dive in. 𝟭. 𝗖𝗿𝗲𝗮𝘁𝗶𝗼𝗻𝗮𝗹 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀  🔹 Singleton: Use when a single instance of a class is needed. Some examples are logging and database connections.   🔹 Factory Method: Decouple object creation from usage. For example, you create different types of database connections based on configuration.  🔹 Abstract Factory: Create families of related objects. For example, I build parsers for different file formats (e.g., JSON, XML, CSV).  🔹 Builder: Constructing complex objects step by step. For example, if you need to create a complex domain object.  🔹 Prototype: Creating duplicate objects and reusing cached objects to reduce database calls. 𝟮. 𝗦𝘁𝗿𝘂𝗰𝘁𝘂𝗿𝗮𝗹 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀  🔹 Adapter: Make incompatible interfaces compatible. For example, it integrates a new logging library into an existing system that expects a different interface.  🔹 Composite: Represent part-whole hierarchies. For example, graphic objects in a drawing application can be grouped and treated uniformly  🔹 Proxy: Control access to objects. For example, lazy loading of a high-resolution image in a web application.  🔹 Decorator: Dynamically add/remove behavior. For example, we are implementing compression or encryption on top of file streams.  🔹 Bridge: Decouple abstraction from implementation. For example, I am separating platform-specific code from core logic. 𝟯. 𝗕𝗲𝗵𝗮𝘃𝗶𝗼𝗿𝗮𝗹 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀  🔹 Strategy: Define a family of algorithms. These algorithms allow users to choose different sorting or compression algorithms.  🔹 Observer: Maintain a consistent state by being notified of changes and, for example, notifying subscribers of events in a messaging system.  🔹 Command: Encapsulate a request as an object. For example, I implement undo/redo functionality in text or image editor.  🔹 State: Encapsulate state-specific behavior. For example, we are handling different states of a user interface element (e.g., enabled, disabled, selected).  🔹 Template Method: Define the skeleton of an algorithm in operation, deferring some steps to subclasses and implementing a base class for unit testing with customizable setup and teardown steps. Ultimately, we came up with the pattern we needed for our problem. #technology #softwareengineering #programming #techworldwithmilan #softwaredesign