Question

I got a vector of pointers to a base class foo which got a couple of child classes and what I would like to do is based on which child class it is, create a new class of the same instance.

I’ve solved it earlier by having a gigantic for loop which uses typeid to find out what class it is but is there no way to solve it in a more general way?

Basically, something like this is what I’m looking for:

std::vector<foo*> a;
std::vector<foo*> b;

//Store a couple of classes in a and b

b[0] = new typeid(a[0]).name();

Answer 1

One approach is to have a virtual clone() method that returns a pointer to an object of the right type:

struct base 
{
  virtual base* clone()=0;
  virtual ~base() {}
};

struct foo : public base
{
  virtual base* clone() { return new foo(*this); }
};

struct bar : public base
{
  virtual base* clone() { return new bar(*this); }
};

Then your code would be

b[0] = a[0].clone();

In real life code you would return a smart pointer, e.g. an std::unique_ptr<base>.