dependency inversion principle (dependency injection) cpp good example

main.cpp

#include <iostream>
using namespace std;

__interface IService {
	void ProvideService();
};

class Police : public IService {
	// ...
	void ProvideService() override {
		cout << "Успокаиваю буйных соседей...\n";
	}
};

class Doctor : public IService {
	// ...
	void ProvideService() override {
		cout << "Выписываю рецепт на аспирин...\n";
	}
};

// class Fireman, PizzaCourier, Plumber, Electrician, InternetProvider etc

class Person {
	IService* worker = nullptr;

public:
	void SelectService(IService* injected_worker) {
		worker = injected_worker; // low coupling - привязка к типу абстракции
	}

	~Person() {
		// no need to do delete here!
	}
	
	void SolveProblem() {
		if (worker != nullptr)
			worker->ProvideService();
	}
};

int main() {
	setlocale(0, "");

	Person person;

	IService* service = new Doctor;
	person.SelectService(service);
	person.SolveProblem();
	delete service;

	service = new Police;
	person.SelectService(service);
	person.SolveProblem();
	delete service;
}