components.cpp

class Base
{
  public:
    Base() {}
    virtual ~Base() {}
};

class NotCopyable
{
  public:
    NotCopyable() {}
    NotCopyable(const NotCopyable &) = delete;
    NotCopyable &operator=(const NotCopyable &) = delete;
};

class FirstComponent : public NotCopyable
{
  public:
    FirstComponent(float value) : _value(value) {}
    virtual ~FirstComponent() {}

    float _value;
};

class SecondComponent : public NotCopyable
{
  public:
    SecondComponent(const std::string &value) : _value(value) {}
    virtual ~SecondComponent() {}

    std::string _value;
};

class GameObject : public Base, public FirstComponent, public SecondComponent
{
  public:
    GameObject() : Base(), FirstComponent(42.0f), SecondComponent(R"(I'm a GameObject!)") {}
    virtual ~GameObject() {}
};

class GameObject2 : public Base, public SecondComponent
{
  public:
    GameObject2() : Base(), SecondComponent(R"(And I'm a GameObject2)") {}
    virtual ~GameObject2() {}
};

int main()
{
  std::vector<std::shared_ptr> objects;
  objects.push_back(std::make_shared<GameObject>());
  objects.push_back(std::make_shared<GameObject2>());

  int order = 0;
  std::for_each(objects.begin(), objects.end(), [&] (std::shared_ptr object) {
    if(auto firstComponent = std::dynamic_pointer_cast(object))
    {
      std::cout << "The object at " << order << " implements FirstComponent" << std::endl;
      std::cout << _value << std::endl;
    }
    if(auto secondComponent = std::dynamic_pointer_cast(object))
    {
      std::cout << "The object at " << order << " implements SecondComponent" << std::endl;
      std::cout << _value << std::endl;
    }
    order++;
  });

  return 0;
}