How do you ensure that your interfaces are segregated and not bloated?

1 Use role-based interfaces

Instead of defining a single interface that contains all the methods that a class might need, consider splitting it into smaller interfaces that correspond to different roles or responsibilities. For example, if you have a class that implements both an IReader and an IWriter interface, you can segregate them into two separate interfaces and let the clients depend only on the one they need. This way, you avoid imposing unnecessary dependencies and coupling.

2 Avoid optional methods

Another sign of a bloated interface is the presence of optional or default methods that are not essential for the interface's purpose. For example, if you have an interface that defines a CRUD (create, read, update, delete) operation, but some of the implementations do not support the update or delete methods, you are violating the ISP. A better approach would be to create separate interfaces for each operation and let the clients choose which ones to depend on.

3 Use composition over inheritance

Inheritance can sometimes lead to bloated interfaces, especially when you have a deep or complex hierarchy of classes that inherit from each other. For example, if you have a base class that defines a common interface for all subclasses, but some of the subclasses do not need or use some of the methods, you are creating unnecessary dependencies and violating the Liskov substitution principle (LSP), another SOLID principle. A better approach would be to use composition instead of inheritance, and delegate the behavior to smaller and more cohesive components.

4 Refactor and simplify

Sometimes, bloated interfaces are the result of poor design decisions, lack of clarity, or changing requirements. In such cases, it is important to refactor and simplify your code to eliminate redundant, unused, or irrelevant methods. You can use tools like code analysis, code metrics, or code smells to identify and remove the sources of bloat in your interfaces. You can also apply design patterns, such as adapter, facade, or decorator, to simplify or enhance your interfaces.

5 Follow the single responsibility principle

Finally, one of the best ways to ensure that your interfaces are segregated and not bloated is to follow the single responsibility principle (SRP), another SOLID principle, which states that every class or module should have one and only one reason to change. By adhering to the SRP, you can avoid creating interfaces that have too many or unrelated methods, and instead create interfaces that are clear, concise, and consistent.

6 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?