Object slicing revisited

Question

Hi, I still don't get how to avoid object slicing...

std::vector<Base*> vec = { new Derived(), new Derived() };

Using smart pointers will cause the objects to get created and destroyed on the same line. I still want to use the vector's contents afterwards... But if I do the memory management manually like above, the base class' constructor keeps getting called, which leads me to not being able to call functions declared in the derived class :( Any help would be appreciated

EDIT: The code above is just for illustration

Answer 1

Thanks Dennis, here is basically what I'm trying to do(DON'T MIND THE MEMORY LEAK, I'll fix that later :P).
https://code.sololearn.com/cFGYCk8uknJ6/?ref=app

Answer 2

It's because operator<< is not a virtual function so the function does not appear in the class' virtual table and therefore it does not get called through polymorphism.

Sadly, a friend function or operator can't be virtual so you have to do a little workaround.

In both classes define this function:

virtual void print() const {
std::cout << *this;
}

The inheriting classes should also mark it as override for good practice.
virtual void print() const override {
std::cout << *this;
}

( virtual is optional in the inheriting classes, but I like to type it anyway unless the class itself is marked as final, it will still be virtual even without the keyword )

Then, back at main call it like

v.at(0)->print();

You could also move the entire definition of the friend operator to the print function, that's up to you.

Answer 3

Right, thanks for the insight Dennis. The code now works as it should, although I did the virtual friend simulation with inline functions. https://code.sololearn.com/cFGYCk8uknJ6/#cpp

Answer 4

Thanks anyways it really helped!

Answer 5

Can I see the rest of the code?
There is nothing wrong with your vector.

Here is an example using unique_ptr though:
https://code.sololearn.com/cSL6v9kiKmng

Answer 6

That's a good solution too, I just went for the shorter answer because I was using my phone. :)