Vector like protected attribute?

[vittorioc98]

is there a possibility to create a vector in the base class and then inherit it?

[Enoizat]

to create a vector in the base class and then inherit it

Like what?
Like this:

#include <vector>

class MyClassOne {
private:
    std::vector myvec;
};

class MyClassTwo : public MyClassOne {};

Or like this:

#include <vector>

class MyVec : public std::vector {};

[vittorioc98]

I mean, if i have a program like this:

class DerivedClass1: public BaseClass{

private:
    vector<unique_ptr<BaseClass>> vec;
    ....
}

class DerivedClass2: public BaseClass{

private:
    vector<unique_ptr<BaseClass>> vec;
    ....
}

I would prefer to insert the vector in the base class and then inherit it in derivatives

Like this

class BaseClass{

protected:
    vector<unique_ptr<BaseClass>> vec;
    .....

}

Is it possible?

[Enoizat]

Well, it seems to work:

#include <iostream>
#include <memory>
#include <vector>

class BaseClass {
public:
    int id {};
    BaseClass() = default;
    BaseClass(int id_arg)
        : id { id_arg }
    {
    }
    void addElemToVec(int id_arg)
    {
        vec.emplace_back(std::make_unique<BaseClass>(id_arg));
    }
protected:
    std::vector<std::unique_ptr<BaseClass>> vec;
// friend:
    friend std::ostream& operator<<(std::ostream & os, const BaseClass & rhs)
    {
        return (os << rhs.id);
    }
};


class DerivedClass : public BaseClass {
// friend:
    friend std::ostream& operator<<(std::ostream & os, const DerivedClass & rhs)
    {
        for(const auto & e : rhs.vec) {
            os << e.get()->id << ' ';
        }
        return os;
    }
};


int main()
{
    DerivedClass dc;
    dc.addElemToVec(1);
    dc.addElemToVec(2);
    dc.addElemToVec(3);
    std::cout << dc << '\n';
}

Have you already taken std::reference_wrapper into consideration?
https://en.cppreference.com/w/cpp/utility/functional/reference_wrapper