Downcasting from base pointer to templated derived types

Question

I have the following hierarchy:

class base
{
public:
   virtual ~base(){}
   virtual void foo() {}
};

template 
class derived1 : public base
{         


        

Answer 1

Insert a non-templated class inbetween base and derived1 or derived2:

class base
{
public:
   virtual ~base() {}  // **NOTE** Should be virtual
   virtual void foo() {}
};

class derived1_base : public base
{
};

template 
class derived1 : public derived1_base
{
public:
   virtual void foo() {}
};

class derived2_base : public base
{
};

template 
class derived2 : public derived2_base
{
public:
   virtual void foo() {}
};

In a comment, you mentioned:

[I want to] call a particular function for each one - btw there's more than derived1 and derived2

Add that (virtual) function to derived1_base, and you don't even need to know T anymore.

if (dynamic_cast(foo))
{
  std::cout << "is derived1";
  dynamic_cast(foo)->specific_derived1_function();
}
else if (dynamic_cast(foo))
{
  std::cout << "is derived2";
  dynamic_cast(foo)->specific_derived2_function();
}

NOTE: I consider a list of dynamic_cast<> a code smell, and I urge you to rethink your approach.