Access to object's fields by using pointer arithmetic

Normally a method uses its object's field by using their name. It's presented below, where we want to get value of description field from getDescription method.

class Car {
    std::string getDescription() {
        return description; // <- we return value of this field
    }

    std::string description;
};

The same result can be obtained by using a bit of magic with this, pointers and casting:

#include <iostream>

class Car {
public:
    Car (int _weight, int _maxSpeed, std::string _description) :
        weight(_weight), maxSpeed(_maxSpeed), description(_description) {
    }
    std::string getDescription() {
        return description;
    }
    std::string getDescriptionUsingThisKeyword() {
        return *((std::string*)((int*)this + 2));
    } 
private:
    int weight, maxSpeed;
    std::string description;
};

int main() {
    Car myCar(200, 200, "my best car ever");
    std::cout << myCar.getDescription() << std::endl;
    std::cout << myCar.getDescriptionUsingThisKeyword() << std::endl;
}

Output:

bash-3.2$ ./a.out 
my best car ever
my best car ever

It's error-prone, e.g. when someone changes order of fields in the class. I think, that it's cool but I wouldn't like to see this in a real code :)