Vector of derived class objects using shared_ptr

Question

I have these classes:

class Element{
};
class Button : public Element{
};
class Label : public Element{
};
class Input : public Element{
};

And I want to be able to create a void add(const Element & e) function that would insert derived class object into a vector of shared_ptrs. The answers I've found suggested something like this:

vector<shared_ptr<CElement>>> vec;
vec.push_back(make_shared<DerivedClass>());

Which could work if I made an overloaded add function for each derived class, but that seems like a miserable solution.

So my question is: How do I insert a derived class object into a vector<shared_ptr<CElement>>> without knowing what derived class I'm trying to insert?

Answer 1

That's the beauty of casting. Your derived classes can be downcasted to the base class.

void add(std::shared_ptr<Element> ptr) {
    vec.push_back(ptr);
}

add(std::make_shared<Button>()); // std::shared_ptr<Button> casted to std::shared_ptr<Element>

Just don't forget to have a virtual destructor in your base class to avoid resource leaks!