C++ base class reference initialize with different derived class object

Question

class Base
{
public:
    void operator()() { func(); }
private:
    virtual void func() {}
};

class Derived1 : public Base
{
private:
    void func() override {/*do something*/}
};

class Derived2 : public Base
{
private:
    void func() override {/*do something else*/}
};

Because I want to use operator overloading,
Reference is a better option than pointer.

What I intend to do is like:

if (condition) {
    Base& obj = Derived1();
} else {
    Base& obj = Derived2();
}

But obj will be destroyed and end of scope.

Base& obj;
if (condition) {
    obj = Derived1();
} else {
    obj = Derived2();
}

Will not work either,
Because reference need to be initialized on declaration.

If I try:

Base& obj = condition ?
    Derived1() : Derived2();

Still an error, Because ternary operator expect convertible type.

What is the best solution to deal with this problem?

Answer 1

You can not use ?: in this case as Derived1 and Derived2 are different types.

One possible way is to use pointer, this is valid:

condition ? pObj.reset(new Derived1()) : pObj.reset(new Derived2());

Or

#include <memory>
std::unique_ptr<Base> pObj;
if (condition)
{
    pObj.reset(new Derived1());
}
else
{
    pObj.reset(new Derived2());
}

You could call operator() this way:

(*pObj)();