I'm trying to use the static polymorphism and template to create a container that can hold more the one type, from what I know about template it can't be done, but I'm hoping that I'm wrong and there is a way. I have the following classes:
template<class Derived>
class base
{
public:
base(string);
void clean()
{
cout << "I'm cleannig \n";
}
void process()
{
static_cast<Derived*>(this)->setup();
static_cast<Derived*>(this)->run();
static_cast<Derived*>(this)->cleanup();
}
string name;
};
template<class Derived>
base<Derived>::base(string y):name(y)
{
}
class derived : public base<derived>
{
friend class base<derived>;
void setup() {cout << "derived setup \n"; }
void run() { cout << "derived run \n"; }
void cleanup() { cout << "derived cleanup \n"; }
};
class derived1 : public base<derived1>
{
friend class base<derived1>;
void setup() {cout << "derived1 setup \n"; }
void run() { cout << "derived1 run \n"; }
void cleanup() { cout << "derived1 cleanup \n"; }
};
and I wont to create a container that can hold them, I tried this code -
template <class T>
class Y{
public:
std::vector<base<T>> m_vec;
};
template <typename T>
class D:public Y<T>
{
public:
friend class Y<T>;
void print()
{
for(auto& e: Y<T>::m_vec)
{
e.process();
}
}
};
int main()
{
base<derived>* b = new base<derived>;
base<derived1>* c = new base<derived1>;
D<derived> y;
y.m_vec.push_back(b);
y.m_vec.push_back(c);
y.print();
}
but its not working i tryed to do this:
y.m_vec.push_back(static_cast<base<derived>>(c));
and I'm getting this error:
error: no matching function for call to ‘std::vector, std::allocator > >::push_back(base*&)’ y.m_vec.push_back(b);
after some testing and digging the answer is that there isn't a way to do it. but you can use std::any like @formerlyknownas_463035818 suggested declare the std::vector as :
std::vector<std::any> m_vec;
Instead of
std::vector<base<T>> m_vec;
and use the boost demangle function to get the type -
std::string name(boost::core::demangle(e.type().name()));
and then use some kind of factory functio to any_cast to the type you need
if(!name.compare("base<derived1>*") )
{
try {
auto* r = any_cast<base<derived1>*>(e);
r->process();
}
catch(const std::bad_any_cast& e) {
std::cout << e.what() << '\n';
}
}
else
{
try {
auto *r = any_cast<base<derived> *>(e);
r->process();
}
catch(const std::bad_any_cast& e) {
std::cout << e.what() << '\n';
}
}
or instead of using the demangle name and use string compare you can use the type() function of the class any and compare is to the typeid like this:
if(e.type()==typeid(base<derived1>*))