Question

Is there some solution or I have to keep exactly class types?

//header file

Class Car {
public:
    Car();
    virtual ~Car();
};

class Bmw:Car {
public:
    Bmw();
    virtual ~Bmw();
};

void Start(Car& mycar) {};

//cpp file

Car::Car(){}
Car::~Car() {}

Bmw::Bmw()
    :Car::Car(){}
Bmw::~Bmw() {}

int main() {
    Car myCar;
    Bmw myBmw;

    Start(myCar); //works
    Start(myBmw); //!! doesnt work

    return 0;
}

Answer 1

C++ defaults to private inheritance, so, you need to declare Bmw as:

class Bmw:public Car

Also, to be completely accurate, you should really have Start as a virtual method of Car and override it as needed in descendant classes. 🙂