boost multi index - loop through key value of specific entry - boost-multi-index

Question

I have a multi index with 2 indexes(in real code, they are of different type).
class CrUsersKeys{
int IMSI;
int TIMESTAMP;
}
After i find an entry in the multi index, I have the iterator of the entry.
auto it = multi.GetIteratorBy<IMSI_tag>(searchKey);
Now i want to loop through all the indexed members in this specific (*it) and check them. Note that i don't want to iterate through the iterator, but through the the indexed element of CrUsersKeys. How can i do it?
for(key in it)
{
if(isGoodKey(key))
std::cout<<"key "<<key <<" is good key"<<std::endl;
}
So it should check isGoodKey((*it).IMSI) and isGoodKey((*it).TIMESTAMP).
CrUsersKeys is template parameter, so i can't really know the members of CrUsersKeys.
Code example at http://coliru.stacked-crooked.com/a/d97195a6e4bb7ad4
My multi index class is in shared memory.

Answer 1

Your question has little to do with Boost.MultiIndex and basically asks for a way to compile-time iterate over the members of a class. If you're OK with CrUsersKeys being defined as a std::tuple (or a tuple-like class), then you can do something like this (C++17):
Edit: Showed how to adapt a non-tuple class to the framework.
Live On Coliru
#include <tuple>
template<typename Tuple,typename F>
bool all_of_tuple(const Tuple& t,F f)
{
const auto fold=[&](const auto&... x){return (...&&f(x));};
return std::apply(fold,t);
}
#include <iostream>
#include <type_traits>
bool isGoodKey(int x){return x>0;}
bool isGoodKey(const char* x){return x&&x[0]!='\0';}
template<typename Tuple>
bool areAllGoodKeys(const Tuple& t)
{
return all_of_tuple(t,[](const auto& x){return isGoodKey(x);});
}
struct CrUsersKeys
{
int IMSI;
const char* TIMESTAMP;
};
bool areAllGoodKeys(const CrUsersKeys& x)
{
return areAllGoodKeys(std::forward_as_tuple(x.IMSI,x.TIMESTAMP));
}
int main()
{
std::cout<<areAllGoodKeys(std::make_tuple(1,1))<<"\n"; // 1
std::cout<<areAllGoodKeys(std::make_tuple(1,"hello"))<<"\n"; // 1
std::cout<<areAllGoodKeys(std::make_tuple(1,0))<<"\n"; // 0
std::cout<<areAllGoodKeys(std::make_tuple("",1))<<"\n"; // 0
std::cout<<areAllGoodKeys(CrUsersKeys{1,"hello"})<<"\n"; // 1
std::cout<<areAllGoodKeys(CrUsersKeys{0,"hello"})<<"\n"; // 0
std::cout<<areAllGoodKeys(CrUsersKeys{1,""})<<"\n"; // 0
}