What are some best practices for designing cohesive and loosely coupled modules and components?

When we receive the project development requirements, the first thing we do is analyze the business requirements together. Then, the development team will break down the business into domains and subdomains. From these subdomains, we will define the entities and behaviors (Abstraction). Entities and behaviors that are closely related and connected will be grouped into a module to ensure Single Responsibility. Next, we will establish communication between the modules, which can be through APIs, message brokers, etc.

"Start with clarity: Identifying responsibilities is crucial for cohesive and loosely coupled design." To properly assign responsibilities: - Establish Clearly Defined Boundaries: Describe the responsibilities of each module using strategies such as use cases and user stories. - Sort by Function: To guarantee strong cohesiveness, classify duties according to importance and resemblance. - Level of Abstraction: Ensure simplicity and concentration by assigning responsibilities to the proper level. - Tools: To see and fine-tune module responsibilities, use CRC cards. It is possible to establish a strong basis for modular and maintainable design by properly allocating roles.

In this section, it’s important to highlight that identifying responsibilities is a key step in ensuring clean design. When a module or component has clearly defined responsibilities, it becomes easier to manage, maintain, and evolve. By assigning functions based on their purpose and grouping similar tasks together, developers can avoid unnecessary complexity. It’s also crucial to balance abstraction levels so that each module only focuses on what it needs to do. Using tools like user stories or CRC cards helps teams visually organize tasks and responsibilities, leading to better cohesion and minimizing overlap across components.

An important responsibility to identify is the concurrency requirements/expectations of the module. It will significantly impact all the design steps.

The following best practices can help in creating well-structured, independent modules and components: 1. Promote low coupling via the interface segregation principle (ISP), dependency injection (DI), dependency inversion principle (DIP), event-driven architecture (EDA), and well-defined interfaces. 2. Increase cohesion via the single responsibility principle (SRP), favoring composition over inheritance and using encapsulation and information hiding. 3. Facilitate flexibility and extensibility by minimizing the impact of changes, adopting a layered architecture, and preferring composition over inheritance. 4. Enable scalability and modularity using modular programming, microservices architecture, and well-defined interfaces.

Apply the Single Responsibility Principle (SRP) for coherence and clarity. Focus begets greatness. - Singular Focus: Make sure every module or component serves a single, distinct goal to reduce the need for changes. - High Cohesion: Modules maintain coherence and manageability by concentrating on a particular duty. - Decreased Dependencies: SRP reduces interdependencies, which lessens the impact of changes. - Clarity and Consistency: Modules become easier to maintain and scale as they become more standardized and straightforward. By implementing SRP, a strong architecture with clearly defined components and segregated modifications is produced, guaranteeing system stability.

In this section, the single responsibility principle (SRP) is about keeping each module or component focused on one task. When a module only has one reason to change, it becomes more predictable and easier to manage. This reduces the risk of unexpected issues when making updates because the changes stay within that module's responsibility. SRP helps create clearer, more organized code by limiting what each component should handle. This approach not only makes the system more cohesive but also prevents the modules from being too dependent on each other, leading to better flexibility and easier maintenance.

To increase cohesion, apply the single responsibility principle (SRP) by ensuring each module or class has one clear purpose or responsibility, making it easier to maintain and understand. Favor composition over inheritance, as composition allows combining behaviors in a more flexible, focused manner. Utilize encapsulation by hiding internal implementation details and exposing only necessary functionality, ensuring each module operates independently and is self-contained. Information hiding strengthens cohesion by restricting direct access to internal workings, preventing external modules from manipulating the internal state.

The interface segregation principle (ISP) encourages creating smaller, focused interfaces that only include what a module or component truly needs. By keeping interfaces specific and avoiding large, general ones, developers ensure that modules don’t have to depend on or implement things they don’t use. This reduces unnecessary complexity and makes the system easier to modify. It also allows modules to change independently without impacting others. Applying ISP leads to more flexible, reusable code, as it minimizes the connections between components and allows each part to evolve more smoothly.

Less is more: Embrace the Interface Segregation Principle (ISP) for flexible and decoupled systems. - Specific Interfaces: Avoid creating bloated, all-purpose interfaces by instead designing small, targeted interfaces that address particular needs. - Decreased Dependencies: Make sure that modules and components only rely on the interfaces that they utilize, reducing superfluous coupling. - Reusability: ISPs facilitate flexibility by enabling simple implementation modifications that don't affect customers. - Reduced Maintenance: Codebases with smaller interfaces are easier to modify and update, making upgrades and modifications easier. Applying ISP improves adaptability and modularity, creating systems that are more resilient and scalable.

I observed that considering the potential extensions of an interface are invaluable for supporting backwards compatibility. Any update should never break backwards compatibility, therefore the designers should spend some time explicitly identifying the specific elements that would be the basis for future expansions and label them as such, even possibly adding "optional" fields as place holders.

To promote low coupling, apply the interface segregation principle (ISP) to ensure that clients only depend on the needed methods, avoiding unnecessary dependencies. Use dependency injection (DI) to inject dependencies rather than hard-coding them, allowing easy swapping of implementations. The dependency inversion principle (DIP) encourages reliance on abstractions rather than concrete implementations, further decoupling high- and low-level components. Event-driven architecture (EDA) allows independent modules to communicate through events, reducing direct dependencies. Finally, we should use well-defined interfaces to clearly define module boundaries.

Separate concerns for better architecture: The Dependency Inversion Principle (DIP) ensures that modules depend on abstractions, not concrete implementations. - Decoupling: Increases the independence of modules by reducing reliance on particular implementations. - Abstractions Over Details: Shared abstractions should be the foundation for both high-level and low-level modules. - Improved Testability: Mocking dependencies makes it simpler to test individual components separately. - Flexibility: Enables simple module upgrades and swaps without interfering with the operation of the entire system. Better scalability and adaptability are supported by DIP's flexible and maintained design.

To enhance flexibility and extensibility, simplify extending functionality, and adapt the system over time with minimal disruption, minimize the scope of changes by designing modules so that changes in one module do not impact others, enabling more accessible updates. Implement a layered architecture, where each layer only interacts with its adjacent layers. This approach allows for the independent evolution and replacement of components without affecting the whole system. Prefer composition over inheritance to enable flexible behavior changes by combining components rather than relying on rigid class hierarchies.

Design patterns provide established methods to structure and manage your software components effectively. They guide the communication and coordination between modules, ensuring clarity and reducing dependencies. Examples include: - Factory: Creates objects without specifying the exact class. - Strategy: Encapsulates algorithms to interchange them dynamically. - Observer: Manages communication between objects with a one-to-many relationship. - Mediator: Centralizes complex communication and control logic. - Adapter: Enables incompatible interfaces to work together. - Facade: Simplifies interaction with complex systems. - Decorator: Adds behavior dynamically to objects. Using these patterns enhances system quality

To enable scalability and modularity, adopt modular programming, which involves splitting code into self-contained, independent development, deployment, and scale of reusable modules. Utilize microservices architecture, which allows services to scale horizontally, providing flexibility to scale only the required components. Well-defined interfaces ensure defined boundaries between modules and enable a smooth interaction while remaining independent. This approach reduces interdependencies, allowing straightforward scaling, maintenance, and upgrades without affecting the whole system.

Refactoring and reviewing are key to maintaining cohesive and loosely coupled components. Refactor your code regularly to: - Eliminate Duplication: Remove redundant code to simplify maintenance. - Reduce Complexity: Streamline logic for clearer, more efficient modules. - Enhance Consistency: Ensure uniformity across the codebase, aligning with design principles. Review your code to: - Catch Errors: Identify and fix bugs and inconsistencies. - Enforce Standards: Verify adherence to cohesion and coupling principles. - Gain Insights: Collaborate with peers for diverse perspectives and improvements. You can use some tools to do this for you, like SonarQube, Resharp, Copilot etc

When Designing modules and components, documentation is really important, specifically documentation around the limitations of your module. Good modules need to have proper documentations to let other developers know how to properly use them, and what order of operations is necessary to keep the module in a valid state