[Boost-users] Collections of shared_ptr<Base> and shared_ptr<Derived>

From: Keith Weintraub (Keith_at_[hidden])
Date: 2005-11-16 10:17:07

Folks,

            What is the best way to pass a
std::vector<boost::shared_ptr<Derived> > to a function that expects a
std::vector<boost::shared_ptr<Base> >?

 

Can I use a cast or should I create a new
std::vector<boost::shared_ptr<Base> > by iterating over the
std::vector<boost::shared_ptr<Derived> >?

 

Here is some sample code. What f is doing is not important it is just an
example:

 

class A { // This class is from a library I have no control over.

   public:

       virtual string getName() { return string("A");}

};

 

class B : public A  { // I need to create B from A to have extra
functionality 

   public:

       virtual string getName() { return string("B");}

       virtual string getLongName() { return string("This is B");}

};

 

void f(std::vector<boost::shared_ptr<A> > &v) {  // This function is
from a library that I have no control over.

       for(int i = 0; i < v.size(); i++)

              cout << v[i]->getName();

}

 

 

int main(char *argv, int arc) {

       std::vector<boost::shared_ptr<B> > bvec(10);

       

       boost::shared_ptr<B> bPtr(new B);

 

       bvec[0] = bPtr;

 

       f(bvec); // This should not compile. <-------------------------

}

 

 

The last line (with the arrow) won't compile because
std::vector<boost::shared_ptr<B> > cannot be converted to
std::vector<boost::shared_ptr<A> >.