How do you use interfaces to achieve loose coupling?

1 What is polymorphism?

Polymorphism is the ability of an object to take on different forms depending on the context. For example, if you have an interface called Animal, and different classes that implement it, such as Dog, Cat, and Bird, you can create an array of Animal objects and call the same method on each of them, such as makeSound(). Each object will perform the method differently, according to its own implementation. This way, you can write code that is generic and reusable, and that does not depend on the specific details of each class.

2 What is dependency inversion?

Dependency inversion is a principle that states that high-level modules should not depend on low-level modules, but both should depend on abstractions. Abstractions are interfaces or abstract classes that define the essential features of a concept, without specifying the details. For example, if you have a high-level module called Printer, and a low-level module called InkCartridge, you should not make Printer depend on InkCartridge directly, but on an interface called ICartridge, that defines the methods and properties that any cartridge should have. This way, you can change or replace the low-level module without affecting the high-level module, as long as it conforms to the interface.

3 How to use interfaces in code?

In order to use interfaces in code, you must first define the interface using the keyword interface and name it according to its purpose. Then, declare the methods and properties that the interface requires, without providing any implementation. After that, implement the interface in one or more classes using the keyword implements and provide the implementation for each method and property. Additionally, use the interface as the type of a variable, parameter, or return value, and assign or pass an object of a class that implements the interface. Finally, invoke the methods and properties of the interface on the object so that it can perform its behavior according to its own implementation.

4 What are the benefits of using interfaces?

Using interfaces can provide several benefits for your code, such as enhancing modularity and cohesion, improving flexibility and extensibility, facilitating testing and mocking, and promoting code reuse and readability. By separating the concerns of different components and grouping related behaviors together, you can add new classes or change existing ones without breaking the code that depends on the interface. Additionally, interfaces enable you to isolate and replace dependencies of a class with fake or stub objects that implement the interface. This reduces duplication and complexity, making the code more expressive and understandable.

5 What are the challenges of using interfaces?

Using interfaces can also pose some challenges for your code, such as increasing the number of files and classes, introducing performance and memory overhead, and creating design and naming conflicts. Abstractions and implementations can clutter the project structure and increase the cognitive load, while extra objects and indirections may affect the speed and efficiency of code execution. Additionally, you must select appropriate and consistent names for the interfaces and their methods, while also avoiding too many or too few interfaces which may violate the interface segregation principle.

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?