删除指向指向对象的指针的指针数组

Question

I want to ask one simple question in my program i making some kind of system, for dynamic allocation I am taking array of pointers to pointers like this

Vehicle **temp=new Vehical*[countVehicle];

then

temp[countVehicle-1]=new Car();

You must have understood what I am trying to do. The problem comes when deleting memory. Can you please tell me how to delete memory in this case.

Answer 1

for ( int i = 0; i < countVehicle; ++i)
{
    delete temp[i];  // assert destructor is virtual!
}
delete[] temp;

Make sure destructor in base class, Vehicle , is declared virtual so the correct destructor is called when deleting objects via base class pointer, as it take place in example above.

class Vehicle {
public:
    //...
    virtual ~Vehicle() {}
};

---

However you should consider using a std::vector of smart pointers, eg

{
  std::vector< boost::shared_ptr<Vehicle> > v;
  v.push_back( boost::shared_ptr<Vehicle>( new Car()));
  v[0]->run(); // or whatever your Vehicle can do
  //...
} // << When v goes out of scope the memory is automatically deallocated.

This will ease memory management.

Answer 2

If you know for sure that the pointers in temp are NULL or a valid allocated Car then:

for(int i = 0; i < countVehicle; ++i)
    delete temp[i];
delete[] temp;

This will only work correctly if Vehicle has a virtual destructor. Otherwise you will not properly destroy each Car.