Re: [Boost-users] [serialization] abstract templatized base class

From: Robert Ramey (ramey_at_[hidden])
Date: 2007-04-01 16:28:26

Ruediger Berlich wrote:

>> From the documentation and the header file "is_abstract.hpp" it
>> appears as
> if using the macro BOOST_IS_ABSTRACT would not work (indeed it
> produces lots of error messages) for templatized classes, but that I
> should instead add the following to the header:

In general, preprocessor macros don't work for templated classes.  This
is described in the manual.
>
> namespace boost {
> namespace serialization {
> template<class T>
> struct is_abstract<myClass<T> > {
>    typedef mpl::bool_<true> type;
>    BOOST_STATIC_CONSTANT(bool, value = true);
> };
> }}
>
> Indeed this seems to work.

so one has to avoid the macro and drop down to the underlying source
code. -  just as you have done.

>
> It appears to me as if another solution might be to use the original
> macro in those files where the templatized classes are first
> instantiated (i.e. "filled" with a type). Please note, though, that
> they are base-classes for some other non-abstract classes, so that
> I'm not sure this would work. Anyway, the idea would be something
> along the lines of
>
> // [...]
> // myClass<myType> is no longer a template
> BOOST_IS_ABSTRACT(myClass<myType>)
>
> class derived
>  :public myClass<myType>
> { ...};

I believe that above would also work.  Of course you have to do it
for every "myType" so some of the convenience of the macro is lost
but currently I see no other way.

Robert Ramey