Question

EDIT:

I realized that this code compiles and works:

#include <iostream>

template<class Something> class Base {
public:
    Base() {

    }

    virtual ~Base() {
    }

    virtual void method() = 0;
};

class Derived: public Base<std::string> {
public:
    Derived() {

    }

    virtual ~Derived() {

    }

    void method() {
    }
};

template<class Something> class TemplatedClass {
public:
    void method(Base<Something>* base) {
    }
};

class SomeClass: public TemplatedClass<std::string> {
};

int main(int argc, char **argv) {

    Derived* d = new Derived();

    Base<std::string>* b = d;
    Base<std::string>* b1 = dynamic_cast<Base<std::string>*>(d);
    Base<std::string>* b2 = static_cast<Base<std::string>*>(d);

    SomeClass sc;
    sc.method(b);
    sc.method(b1);
    sc.method(b2);
}

Then, I am doing a really big mistake preparing the skeleton or even trying to understand my own code. WHAT a SHAME!!! Sorry… This is a really bad question. It would be better to remove it…

** NO SENSE QUESTION AND CODE BELOW **
Given this:

template<class Something> class Base
{
    virtual void method() = 0;
};

class Derived: public Base<std::string>
{
    void method() { ... };
};

I want to downcast a pointer of Derived to a pointer of Base. I tried to use dynamic_cast with no success:

...
Derived* d = new Derived();
Base* b = dynamic_cast<Base*>(d);
...

I always got errors during execution.

I don’t know if I need downcasting,. I have this situation:

template<class Something> class TemplatedClass
{
    void method(Base<Something>* base) { ... };
};

class SomeClass : public TemplatedClass<std::string> { ... };

And I want to call (EDITED*):

Derived* d = new Derived();

SomeClass sc;
sc.method(d);

But it gives me an conversion error.

What does I need? Downcasting or what?

Answer 1

Presumably your test actually looked like this?

Base<std::string>* b = dynamic_cast<Base<std::string> *>(d); 

i.e. it has to be a cast to the instantiated template, not Base without a type argument.

Wait a second – you’re doing derived to base!

Base<std::string>* b = d; 

That should be fine!

Your second example doesn’t look right – in particular:

SomeClass sc();

That should be:

SomeClass sc;

Can you post the real code and the exact error message?