Trevor
I am currently learning C++. I have a parent class (**Vehicle**) and two subclasses (**Car** and **Boat**). I am wondering how to create an object that will either be Car or Boat, depending on what the user specifies.
Below is my best attempt. It compiles and runs, but doesn't do what I want. It is supposed to make `*vh` a Car or Boat, but `*vh` always remains a Vehicle.
```
#include <iostream>
using namespace std;
class Vehicle
{
public:
void print(void)
{
cout<<"this is a vehicle\n";
}
};
class Car: public Vehicle
{
public:
void print(void)
{
cout<<"this is a car\n";
}
};
class Boat: public Vehicle
{
public:
void print(void)
{
cout<<"this is a boat\n";
}
};
int main()
{
Vehicle *vh = new Vehicle();
Car *cr = new Car();
Boat *bt = new Boat();
int x;
cout<<"type 0 for car and 1 for boat: ";
cin>>x;
if(x==0)
{
cout<<"you chose car\n";
vh = cr;
}
else if(x==1)
{
cout<<"you chose boat\n";
vh = bt;
}
vh->print();
}
```
Top Answer
Anonymous 11738
You need to mark your `print` method `virtual`:
void virtual print(void)
Then, in your other classes, you need to `override` them:
void virtual print(void) override
This will get you the desired behavior.
On a side note, you are not `delet`ing your objects at the end of the program, which causes you to have a memory leak. Furthermore, you overwrite the pointer to `Vehicle` with another pointer. That means your `Vehicle` instance is lost and can’t be accessed by any pointer, therefore it can’t be deleted.
Consider not instancing your Vehicle at all:
Vehicle *vh = nullptr;