[Boost-users] Template instantiation problem

From: Rush Manbert (rush_at_[hidden])
Date: 2006-05-10 18:30:08

I have a template class that is designed to contain built in types or 
std::string types. I always need to be able to cast an instance of the 
class as a std::string, and I also need to be able to cast it as the 
parameter type with which it was instantiated.

In my class definition, I have defined two cast operators, like so:
(Extraneous stuff omitted)

template<typename T>
class MyDataObject : public MyDataObjectBase
{	

        // Cast as std::string
        inline			operator const std::string & 	()
                                {
                                        ...some code here
                                }
                
        // Cast as T
        inline			operator const T &		()
                                {
                                        ...some code here
                                }
}

The original code was written on a Mac and compiled with Gnu, which did 
not complain. even when I did this:

class MyStringObjectClass : public MyDataObject<std::string>
{
}

Now, however, I have moved the code to Windows, and the Visual Studio 
compiler complains about the second cast operator when I define 
MyStringObjectClass.

I thought that if I could conditionally define the cast as T operator 
(or the cast as std::string) I would be okay, but that means testing 
against the value of T with the preprocessor. I don't see how to do 
that, but I know that some of you folks are really good at bending the 
preprocessor to your will.

Can anyone show me a way out of this predicament?

Thanks,
Rush