CODESAMPLE

Clean Architecture - C++

Clean Architecture C++

The Clean Architecture pattern separates the application into concentric layers: Entities (core business rules), Use Cases (application-specific logic), Interface Adapters (translates data between layers), and Frameworks & Drivers (UI, databases, etc.). Dependencies point inwards – outer layers depend on inner layers, but inner layers have no knowledge of outer ones. This promotes testability, maintainability, and independence from frameworks.

This C++ implementation focuses on the core principle of dependency inversion. Entities are simple data classes. Use Cases define application operations, depending only on Entity interfaces. Interface Adapters (e.g., Presenter) receive data from Use Cases and format it for the outer layer. The main function represents Frameworks & Drivers, orchestrating calls but remaining separate from business logic. Using interfaces and dependency injection allows swapping implementations without affecting core logic, aligning with C++ best practices of abstraction and modularity.

#include <iostream>
#include <string>
#include <vector>

// Entities
namespace Entities {
  class User {
  public:
    std::string name;
    int age;
  };
}

// Use Cases
namespace UseCases {
  class UserInteractor {
  public:
    virtual void getUser(int userId, Entities::User& user) = 0;
  };

  class GetUserUseCase : public UserInteractor {
  public:
    void getUser(int userId, Entities::User& user) override {
      // In a real app, this would fetch from a repository.
      // Here, we fake it for simplicity.
      if (userId == 1) {
        user.name = "Alice";
        user.age = 30;
      } else {
        user.name = "Unknown";
        user.age = 0;
      }
    }
  };
}

// Interface Adapters
namespace InterfaceAdapters {
  class Presenter {
  public:
    virtual void presentUser(const Entities::User& user) = 0;
  };

  class ConsolePresenter : public Presenter {
  public:
    void presentUser(const Entities::User& user) override {
      std::cout << "User: Name = " << user.name << ", Age = " << user.age << std::endl;
    }
  };
}

int main() {
  // Frameworks & Drivers (orchestration)
  UseCases::GetUserUseCase userUseCase;
  InterfaceAdapters::ConsolePresenter presenter;

  Entities::User user;
  userUseCase.getUser(1, user);
  presenter.presentUser(user);

  userUseCase.getUser(2, user);
  presenter.presentUser(user);

  return 0;
}