How to achieve “virtual template function” in C++

Question

first off: I have read and I know now that a virtual template member function is not (yet?) possible in C++. A workaround would be to make the class a template and then use

Answer 1

I think the visitor pattern can be a solution.

UPDATE

I finished my example:

#include 
#include 
#include 

class Animal;
class Wolf;
class Fish;

class Visitor
{
    public:
    virtual void visit(const Animal& p_animal) const = 0;
    virtual void visit(const Wolf& p_animal) const = 0;
    virtual void visit(const Fish& p_animal) const = 0;
};

template
class AmountVisitor : public Visitor
{
    public:
    AmountVisitor(AMOUNT p_amount) : m_amount(p_amount) {}
    virtual void visit(const Animal& p_animal) const
    {
        std::cout << "I eat like a generic Animal." << std::endl;
    }
    virtual void visit(const Wolf& p_animal) const
    {
        std::cout << "I eat like a wolf!" << std::endl;
    }
    virtual void visit(const Fish& p_animal) const
    {
        std::cout << "I eat like a fish!" << std::endl;
    }


    AMOUNT m_amount;
};

class Animal {
    public:

        virtual void Accept(const Visitor& p_visitor) const
        {
            p_visitor.visit(*this);
        }

        virtual ~Animal() {
        }
};

class Wolf : public Animal {
    public:
        virtual void Accept(const Visitor& p_visitor) const
        {
            p_visitor.visit(*this);
        }
};

class Fish : public Animal {
    public:
        virtual void Accept(const Visitor& p_visitor) const
        {
            p_visitor.visit(*this);
        }
};

int main()
{
    typedef boost::shared_ptr TAnimal;
    std::vector animals;
    animals.push_back(TAnimal(new Animal()));
    animals.push_back(TAnimal(new Wolf()));
    animals.push_back(TAnimal(new Fish()));

    AmountVisitor amount(10);

    for (std::vector::const_iterator it = animals.begin(); it != animals.end(); ++it) {
        (*it)->Accept(amount);
    }

    return 0;
}

this prints:

I eat like a generic Animal.
I eat like a wolf!
I eat like a fish!