Next.js: Implementing Clean Architecture

Clean Architecture is a software design pattern that aims to create modular, maintainable, and scalable applications. The main principles of Clean Architecture are separation of concerns, dependency inversion, and testability. In this tutorial, I will show you how to implement Clean Architecture in a Next.js application.

Step 1: Set up a Next.js project

First, you need to create a new Next.js project. You can do this by running the following command in your terminal:

npx create-next-app@latest my-clean-architecture-app

This will set up a new Next.js project with the necessary folder structure and dependencies.

Step 2: Create the project structure

Next, you need to create the directory structure for your project. In Clean Architecture, the code is divided into layers, each with a specific responsibility. The typical layers in Clean Architecture are:

• Entities: Contains the domain models and business logic of your application.
• Use Cases: Contains the application-specific use cases.
• Interface Adapters: Contains the implementation details such as UI components, database access, and external API integration.
• Frameworks & Drivers: Contains the external dependencies such as the Next.js framework itself.

Here is an example directory structure for a Clean Architecture Next.js project:

├── components
├── entities
├── pages
├── services

Step 3: Implement the Entities

In the entities directory, you can define the domain models and business logic of your application. For example, if you are building a todo list app, you could define a Todo entity like this:

// entities/Todo.js

export default class Todo {
  constructor(title, completed) {
    this.title = title;
    this.completed = completed;
  }
}

Step 4: Implement the Use Cases

In the services directory, you can implement the application-specific use cases. For example, you could define a TodoService class that handles CRUD operations for todos:

// services/TodoService.js

import Todo from '../entities/Todo';

export default class TodoService {
  constructor() {
    this.todos = [];
  }

  createTodo(title) {
    const todo = new Todo(title, false);
    this.todos.push(todo);
    return todo;
  }

  getTodos() {
    return this.todos;
  }
}

Step 5: Implement the Interface Adapters

In the pages and components directories, you can implement the interface adapters such as React components and API integration. For example, you could create a TodoList component that displays the list of todos:

// components/TodoList.js

import { useEffect, useState } from 'react';
import TodoService from '../services/TodoService';

const todoService = new TodoService();

const TodoList = () => {
  const [todos, setTodos] = useState([]);

  useEffect(() => {
    setTodos(todoService.getTodos());
  }, []);

  return (
    <div>
      {todos.map(todo => (
        <div key={todo.title}>
          <p>{todo.title}</p>
          <p>{todo.completed ? 'Completed' : 'Incomplete'}</p>
        </div>
      ))}
    </div>
  );
};

export default TodoList;

Step 6: Use the components in your Next.js pages

Finally, you can use the interface adapters in your Next.js pages. For example, you could create a pages/index.js file that renders the TodoList component:

// pages/index.js

import TodoList from '../components/TodoList';

const Home = () => {
  return (
    <div>
      <h1>Todo List</h1>
      <TodoList />
    </div>
  );
};

export default Home;

That’s it! You have now implemented Clean Architecture in a Next.js application. This approach allows you to easily test and maintain your code, as well as scale your application as it grows. I hope this tutorial was helpful to you. Happy coding!