Datatypes and polymorphism - c++

Question

I have a design question. I want custom datatypes implementing an interface. For example, using templates is simply (maybe next design isn't correct -because I can do a generic class instead of the next- but clarifies my goal):
template <typename T>
class IDatatype
{
public:
virtual T getData() const = 0;
virtual void setData(T pData) = 0;
};
class MyChar: public IDatatype<char>
{
public:
void setData(char pData){...}
char getData() const{...}
private:
char _data;
};
class MyInt: public IDatatype<int>
{
public:
void setData(int pData){...}
int getData() const{...}
private:
int _data;
};
IDatatype<int> *data = new MyInt(); // parametrized interface, bad idea :(
data->getData(); // it works ok
From previous classes, it is easy to get the attribute corresponding to each _data class member. My question:
Is there any way (change design, etc.) to implement generic setter and getter in IDatatype
and for any type and thus manipulate the _data attribute of each class
without using templates in the interface?
For example:
class IDatatype
{
public:
// pure virtual getters and setters for specialized _data fields. Here is my design question.
};
class MyChar: public IDatatype
{
public:
void setData(char pData){...};
char getData(){...};
private:
char _data;
};
class MyInt: public IDatatype
{
public:
void setData(int pData){...};
int getData(){...};
private:
int _data;
};
IDatatype *intData = new MyInt(); // no parametrized interface!
intData->getData(); // how can I create this method from IDatatype?
IDatatype *charData = new MyChar();
charData->getData(); // the same here
NOTE: I have no good english, apologize for any errors :)

Answer 1

You could probably achieve this in 3 ways, none as elegant and error free as using a template
Define your data as a union of int/float/char in the base class and act on this union from the set/get methods of the base class. The entire VB (old VB 6) class system works on such a data type called VARIANT.
Return void * from base class and cast and use as appropriate - yuck & good luck!!.
Return the base interface reference itself from the getData which though appearing to be meaningful, has no meaning at all.
4.