Retrieve data from heterogeneous std::list

Question

In the below code I am simply trying to experiment with a Heterogeneous std::list where I have stored three Derived class object in a list of type Base*. When retrieving data fr

Answer 1

I would redefine Base to have a virtual method to output the information:

class Base {
    friend std::ostream & operator << (std::ostream &os, const Base &b) {
        b.print(os);
        return os;
    }
    virtual void print (std::ostream &os) const = 0;
public:
    virtual ~Base () {}
};

You are then forced to implement a print method in each derived class. Your print loop would look like:

    for (any_list::iterator itr=l.begin();itr!= l.end();++itr)
        std::cout << **itr;

Your list should avoid managing bare pointers, since you put yourself at risk of leaking memory. You can use a smart pointer instead:

typedef std::list< std::unique_ptr > any_list;

Since unique_ptr requires explicit construction from the pointer, your code that populates the list needs to be updated.

    l.push_back(std::unique_ptr(new Derived1));
    l.push_back(std::unique_ptr(new Derived2));
    l.push_back(std::unique_ptr(new Derived3));