C++ workaroud virtual template method - c++

Question

i know there is nothing like virtual template method in C++, but as it seems it is exactly what i need. Is there any workaround i could use? I am thankful for any suggestion.
I would like to add Entities to a vector by a add method, which need to be virtual and also template, how to avoid this?
#include <iostream>
#include <vector>
class EntityBase {
public:
};
class EntityDerived1 : public EntityBase {
public:
};
class EntityDerived2 : public EntityBase {
public:
};
class ContainerBase {
public:
template<typename T>
virtual void add() = 0; // i know this is not allowed!!!
};
class ContainerConcrete : public ContainerBase {
public:
template<typename T>
void add() override { // i know this is not allowed!!!
data.push_back(std::make_shared<T>());
}
void doSecretStuffWithDataHere() {
// ...
}
private:
std::vector<std::shared_ptr<EntityBase>> data;
};
class Engine {
public:
Engine() :
container(std::make_shared<ContainerConcrete>())
{}
ContainerBase& getContainer() {
auto rawPointer = container.get();
return *container;
}
private:
std::shared_ptr<ContainerConcrete> container;
};
int main() {
Engine engine;
ContainerBase& container = engine.getContainer();
container.add<EntityDerived1>();
container.add<EntityDerived2>();
}

Answer 1

Just make add a regular virtual function that takes shared_ptr as a parameter
class ContainerBase {
public:
virtual void add(std::shared_ptr<EntityBase>) = 0;
};
class ContainerConcrete : public ContainerBase {
public:
void add(std::shared_ptr<EntityBase> p) override {
data.push_back(p);
}
// . . .
And then invoke it with make_shared for the desired type:
int main() {
Engine engine;
ContainerBase& container = engine.getContainer();
container.add(std::make_shared<EntityDerived1>());
container.add(std::make_shared<EntityDerived2>());
}
Alternatively you can add a templated overload that invokes make_shared:
virtual void add(std::shared_ptr<EntityBase>) = 0;
template<typename T>
void add() {
add(std::make_shared<T>());
}