Unlocking the Power of Clean Architecture: A Deep Dive into Related Entity Creation Use Case

As software architects, we strive to create systems that are scalable, maintainable, and easy to understand. One architectural pattern that has gained popularity in recent years is Clean Architecture. In this article, we’ll explore the related entity creation use case in Clean Architecture, providing a comprehensive guide on how to implement it in your projects.

What is Clean Architecture?

Clean Architecture is a software architectural pattern that separates the application’s business logic from its infrastructure and presentation layers. It’s based on the idea that the business logic should be independent of the framework, database, and user interface. This decoupling enables developers to create more modular, flexible, and sustainable systems.

The Clean Architecture Layers

A Clean Architecture system consists of four main layers:

• Entities**: These represent the business domain and are responsible for encapsulating the data and behavior.
• Use Cases**: These define the actions that can be performed on the entities and are responsible for orchestrating the flow of the application.
• Interface Adapters**: These provide the interface between the application and the external world, such as the database, file system, or network.
• Framework and Drivers**: These include the frameworks, libraries, and tools used to build the application.

The Related Entity Creation Use Case

In Clean Architecture, entities are the heart of the system, and creating related entities is a common use case. Related entities are entities that have a logical connection with each other, such as a customer and their orders, or a product and its reviews.

Problem Statement

Let’s consider a simple e-commerce application where we need to create a customer entity and associate it with multiple orders. The traditional approach would be to create a Customer class with an Orders property, which would contain a list of Order objects. However, this approach has several limitations:

• It tightly couples the Customer entity to the Orders entity, making it difficult to change either entity without affecting the other.
• It mixes the business logic of the Customer entity with the infrastructure concerns of storing and retrieving orders.

Solution: Using a Use Case to Create Related Entities

To overcome these limitations, we can create a use case that specifically handles the creation of related entities. Let’s call this use case CreateCustomerWithOrdersUseCase.

public class CreateCustomerWithOrdersUseCase
{
    private readonly IEntityRepository<Customer> _customerRepository;
    private readonly IEntityRepository<Order> _orderRepository;

    public CreateCustomerWithOrdersUseCase(IEntityRepository<Customer> customerRepository, IEntityRepository<Order> orderRepository)
    {
        _customerRepository = customerRepository;
        _orderRepository = orderRepository;
    }

    public async Task<Customer> CreateCustomerWithOrdersAsync(CreateCustomerWithOrdersRequest request)
    {
        var customer = new Customer(request.Name, request.Email);
        var orders = new List<Order>();

        foreach (var orderRequest in request.Orders)
        {
            var order = new Order(orderRequest.ProductId, orderRequest.Quantity);
            orders.Add(order);
        }

        customer.Orders = orders;

        await _customerRepository.AddAsync(customer);
        await _orderRepository.AddRangeAsync(orders);

        return customer;
    }
}

In this example, we’ve created a use case that takes a CreateCustomerWithOrdersRequest object as input, which contains the customer’s details and a list of orders. The use case creates a new customer entity and associates it with the list of orders, ensuring that the business logic is kept separate from the infrastructure concerns.

Benefits of Using a Use Case

By using a use case to create related entities, we’ve achieved several benefits:

• Decoupling**: We’ve decoupled the Customer entity from the Orders entity, making it easier to change either entity without affecting the other.
• Single Responsibility Principle**: The use case has a single responsibility, which is to create a customer with orders, making it easier to maintain and extend.
• Testability**: We can easily test the use case in isolation, without having to worry about the infrastructure concerns.

ImplementationDetails

To implement the CreateCustomerWithOrdersUseCase, we’ll need to create the following entities and repositories:

Entities

public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
    public ICollection<Order> Orders { get; set; }
}

public class Order
{
    public int Id { get; set; }
    public int CustomerId { get; set; }
    public int ProductId { get; set; }
    public int Quantity { get; set; }
}

Repositories

public interface IEntityRepository<T> where T : class
{
    Task<T> AddAsync(T entity);
    Task<IEnumerable<T>> AddRangeAsync(IEnumerable<T> entities);
}

public class CustomerRepository : IEntityRepository<Customer>
{
    private readonly DbContext _context;

    public CustomerRepository(DbContext context)
    {
        _context = context;
    }

    public async Task<Customer> AddAsync(Customer customer)
    {
        _context.Customers.Add(customer);
        await _context.SaveChangesAsync();
        return customer;
    }

    public async Task<IEnumerable<Customer>> AddRangeAsync(IEnumerable<Customer> customers)
    {
        _context.Customers.AddRange(customers);
        await _context.SaveChangesAsync();
        return customers;
    }
}

public class OrderRepository : IEntityRepository<Order>
{
    private readonly DbContext _context;

    public OrderRepository(DbContext context)
    {
        _context = context;
    }

    public async Task<Order> AddAsync(Order order)
    {
        _context.Orders.Add(order);
        await _context.SaveChangesAsync();
        return order;
    }

    public async Task<IEnumerable<Order>> AddRangeAsync(IEnumerable<Order> orders)
    {
        _context.Orders.AddRange(orders);
        await _context.SaveChangesAsync();
        return orders;
    }
}

Conclusion

In this article, we’ve explored the related entity creation use case in Clean Architecture, providing a comprehensive guide on how to implement it in your projects. By using a use case to create related entities, we’ve achieved decoupling, single responsibility principle, and testability. Remember to keep your use cases simple, focused, and easy to understand, and always prioritize the business logic over infrastructure concerns.

Use Case	Description
CreateCustomerWithOrdersUseCase	Creates a customer entity and associates it with multiple orders

Best Practices

• Keep use cases simple and focused: Avoid complex use cases that perform multiple actions.
• Decouple entities from infrastructure concerns: Use repositories and interface adapters to decouple entities from the infrastructure.
• Test use cases in isolation: Write unit tests for use cases to ensure they’re working correctly.

By following these best practices and using a use case to create related entities, you’ll be able to create more maintainable, scalable, and sustainable systems that meet the requirements of your business domain.

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