How to morph an object at runtime while keeping past information? - oop

Question

Is it possible to morph an object at runtime depending on its current state and keep all past information?
Say I have the following (in pseudo-code):
class Vehicle {
int state, lat, long;
void run();
}
class Plane : Vehicle {
void run() {fly();}
}
class Car : Vehicle {
void run() {drive();}
}
class Boat : Vehicle {
void run() {navigate();}
}
void main() {
// Setup code goes here
Vehicle vehicle = new Vehicle();
while(true) {
switch(vehicle->state){
case(1): vehicle = new Plane();
case(2): vehicle = new Car();
case(3): vehicle = new Boat();
}
}
}

Answer 1

It is not possible in the sense you've wrote it, but it is possible to design system with behavior you want:
You have one object, it is the same object during runtime
Object has different behaviors
Current behavior is based on current state
Its small, but very important difference with what you wrote in question, in this approach we're not morphing object, but it's behavior only
There are could be multiple different implementations, depending on full set of requirements, here is simplest one, assuming that behavior changes position only:
class Position {
int lat, long;
}
interface PositionCalculator {
Position calc(Position old);
}
class Vehicle {
private Position pos;
void modify(PositionCalculator calc) {pos = calc.calc(pos);}
}
class CarCalculator : PositionCalculator {
Position calc(Position old) {return navigate(old);}
}
class PlaneCalculator : PositionCalculator {
Position calc(Position old) {return fly(old);}
}
void main() {
Vehicle vehicle = new Vehicle();
PositionCalculator plane = new PlaneCalculator()
PositionCalculator car = new CarCalculator();
while(true) {
if (vehicle is in air)
vehicle.modify(plane);
else if (vehicle is on road)
vehicle.modify(car);
}
}