Re: compile time detection of multiple template class usage

From:
ta0kira@yahoo.com
Newsgroups:
comp.lang.c++.moderated
Date:
Sat, 14 Jul 2007 18:16:17 CST
Message-ID:
<1184445430.879214.288390@g4g2000hsf.googlegroups.com>
On Jun 29, 3:09 pm, "alexandru.nicau" <alexandru.ni...@gmail.com>
wrote:

Hello All,
I've got this huge class hierarchy (the naive solution to the
following cannot be accepted). Throughout the code I need to
instantiate a template wrapper class at several locations. Easy does,
I change the code and wrap all the members I want into TmplWrp. Assume
it's bad if I've got some member wrapped into TmplWrp then one of its
descendants (think of class members - not of inheritance) also wrapped
into TmplWrp.


Let me guess: You are trying to deny access to the wrapped variables
when the parent object is const? The code below seems to work. The
macro will be different if you use a template, but you get the idea.
This provides errors upon attempted instantiation which should lead
back to the embedded declaration.

class wrapper_user
{
protected:
     template <class Type>
     class wrapper
     {
        Type local;

     public:
        Type &get() { return local; }
     };
};

#define STRUCT_WRAPPER(name) class name; \
                              template <> class \
                                wrapper_user::wrapper < name > \
                                { virtual void INVALID_EMBEDDING() =
0; }; \
                              struct name : public wrapper_user

STRUCT_WRAPPER(test_class1)
{
    wrapper <int> value;
};

STRUCT_WRAPPER(test_class2)
{
    wrapper <test_class1> invalid;
};

int main()
{
    test_class1 test1;
    test_class2 test2;

    test1.value.get();
    test2.invalid.get();
}

Kevin P. Barry

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