Re: [Boost-users] [Serialization] is_serializable trait?

23 Jul 2007

      Very clever, I would expect some variation of this to end up somewhere in the library itself some day.

Robert Ramey
  "Roman Perepelitsa"  wrote in message news:OFC1A16EC6.69CEAA30-ONC3257321.002322F2-C3257321.0023748C@db.com...
...
Chris Fairles"  on Fri, 20 Jul 2007 18:03:18 -0400 
How can you determine (compile-time) that a class has a serialize function?
struct foo {
template <typename Archive>
void serialize (Archive &, const unsigned int);
};
"&foo::serialize" isn't a type and I can't figure out a way to make it
a type (besides a typedef in the class) and also a constant
expression.
Tried to play around with this as well but theres no substitution
failure here and static functions can't be constant expressions
(commonnnn c++0x!!)
struct serialize {
    template <typename T>
    static void value(T const&) { void(T::*f)(archive::xml_oarchive &,
const unsigned int) = &T::template serializearchive::xml_oarchive;
(void)f; }
};
Basically, in the code below I want to see "GoodGood" printed out and
the only thing I can change is Q.
struct A{
  void f(int,int){}
};
struct B{};
template 
struct Q{enum{value=false};};
template<class T> struct Q{enum{value=true};};
int main(){
  if(Q<A>::value) { cout << "Good";}
  if(!Q<B>::value){ cout << "Good";}
}
Help/hints/remotely possible?
You can try something like this. 

  #include <iostream> 
  #include <iomanip> 

  typedef char yes_type; 

  struct no_type 
  { 
     char padding[8]; 
  }; 

  template <class T> 
  struct HasSerializeMember 
  { 
      typedef void (T::*SerializationFun)(int &, unsigned); 

      template <SerializationFun> 
      struct A {}; 

      template <class Q> 
      static yes_type Test(A<&Q::serialize>*); 

      template <class Q> 
      static no_type Test(...); 

      static const bool value = 
          sizeof(Test<T>(0)) == sizeof(yes_type); 
  }; 

  struct A 
  { 
      template <class Stream> 
      void serialize(Stream & strm, unsigned version) {} 
  }; 

  struct B 
  { 
  }; 

  struct C 
  { 
      void serialize() {} 
  }; 

  int main() 
  { 
      using namespace std; 
      cout 
          << boolalpha 
          << HasSerializeMember<A>::value << '\n'  // true 
          << HasSerializeMember<B>::value << '\n'  // false 
          << HasSerializeMember<C>::value << endl; // false 
  } 

  Regards,
  Roman Perepelitsa

  Deutsche Bank Moscow
  +7 (495) 660-74-08

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