How can I use overrided function of child objects from a parent object vector?

Question

I want to create a parent class vector and push child objects to that vector. Also, I want to the child object's functions from this vector. My demo is like that:

#include <iostream>
#include <vector>

class A
{
    public:
        virtual void print() { std::cout << "A"; }
};

class B: public A
{
    public:
        void print() override { std::cout << "B"; }
};

class C: public A
{
    public:
        void print() override { std::cout << "C"; }
};

int main()
{
    std::vector<A> list;

    B obj1;
    list.push_back(obj1);

    C obj2;
    list.push_back(obj2);

    for(int i=0; i<list.size(); i++)
        list[i].print();

    //Expected output: BC

    return 0;
}

In C++ polymorphic behavior requires pointers or references. When you push_back your `B` and `C` objects into the `vector`, they get "sliced", so what's in the vector is actually an `A` object, not a `B` or `C` object at all (and being an `A` object, it obviously doesn't act like a `B` or `C` object in any respect).. — Jerry Coffin, Apr 01 '23 at 16:16

score 1 · Accepted Answer · answered Apr 01 '23 at 16:16

You could use a vector of pointers (i.e., vector<A*>), which would allow polymorphism:

int main()
{
    std::vector<A*> list;

    B obj1;
    list.push_back(&obj1);

    C obj2;
    list.push_back(&obj2);

    for(int i=0; i<list.size(); i++) {
        list[i]->print();
    }

    return 0;
}

How can I use overrided function of child objects from a parent object vector?

1 Answers1