c++ - Inheritance reflection in tags -


i'm working on kind of publisher/subscriber block. subscribers subscribe messages tag(s). messages in system organized in hierarchy, i'd tags reflect hierarchy. i've made small piece of code, how i'd see system

class tmsg {};  class tmsg1: public tmsg {};  class tmsg2: public tmsg {};  template<class t> struct tag {};  template<> struct tag<tmsg1>: public tag<tmsg> {};  template<> struct tag<tmsg2>: public tag<tmsg> {};   template<class t> void processmessage(t &t) {     tag<t> ti;     procmsgimpl(ti); }  void procmsgimpl(tag<tmsg>&) {     std::cout << "f" << std::endl; }  void procmsgimpl(tag<tmsg1>&) {     std::cout << "f1" << std::endl; }   int main() {     tmsg t;     tmsg1 t1;     tmsg2 t2;      processmessage(t);     processmessage(t1);     processmessage(t2);     return 0; }

what want avoid in snippet explicit definition inheritance of tags struct tag<tmsg1>: public tag<tmsg> {};, if tmsg base class of tmsg1, i'd tags keep information implicitly.

would work you? idea make tmsg classes inherit wrapper , have generic tag:

#include <iostream>  // use wrapper template <class b> struct base : public b {      using base_type = b; };  class tmsg {};  // inherit wrapper class tmsg1: public base<tmsg> {};  // inherit wrapper class tmsg2: public base<tmsg> {};  // generic tag template<class t> struct tag : public tag<typename t::base_type>{};  // full specialization base class template <> struct tag<tmsg> {};  template<class t> void processmessage(t &t) {     tag<t> ti;     procmsgimpl(ti); }  void procmsgimpl(tag<tmsg>&) {     std::cout << "f" << std::endl; }  void procmsgimpl(tag<tmsg1>&) {     std::cout << "f1" << std::endl; }   int main() {     tmsg t;     tmsg1 t1;     tmsg2 t2;      processmessage(t);     processmessage(t1);     processmessage(t2);     return 0; }

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