Hi everyone, I could need a little advice using boost multiindex as follows: I have a Host class and I want to store HostPtrs in a multiindex container to a) have a member ip() as a key to unique hosts and b) be able to access random hosts via operator[]. The problem as I understand is the shared_ptr. Please consider this: class Host { public: Host(const boost::asio::ip::address &ip) : m_ip(ip) {}; const boost::asio::ip::address &ip(void) const throw () { return m_ip; }; private: Host(void) {}; boost::asio::ip::address m_ip; }; typedef boost::shared_ptr<Host> HostPtr; struct lthost { bool operator()(const HostPtr &h1, const HostPtr &h2) const { return (h1->ip() < h2->ip()); } }; struct giveip { // this is supposedly my key extractor typedef boost::asio::ip::address result_type; const result_type &operator()(const HostPtr &p) const { return p->ip(); }; }; typedef boost::multi_index_container< HostPtr, boost::multi_index::indexed_by< boost::multi_index::ordered_unique<giveip>, boost::multi_index::random_access<> >

HostSet;

typedef HostSet::nth_index<0>::type HostSetOrderedIndex; typedef HostSet::nth_index<1>::type HostSetRandomIndex; Now inserting and accessing elements compiles fine, just when I try to erase something... int main(int argc, char **argv) { HostSet s; HostPtr p1(new Host(boost::asio::ip::address::from_string("127.0.0.1"))); HostPtr p2(new Host(boost::asio::ip::address::from_string("10.10.55.1"))); // now place a pointer to that host in the multiset. HostSetOrderedIndex &oi = s.get<0>(); oi.insert(p1); oi.insert(p2); oi.erase(p1); // booom } Basically, I want the index to access each ptr's ip() function to get the key rather than the ptr itself, which would be just random mem as far as I understand it. So the key extractor should work, shouldn't it? I also tried the lthost() function: typedef boost::multi_index_container< HostPtr, boost::multi_index::indexed_by< boost::multi_index::ordered_unique<boost::multi_index::identity<HostPtr>, lthost>, boost::multi_index::random_access<> >

But that doesn't work either. I guess it's accessing the HostPtr directly instead of dereferencing it. It does compile and also does the job but tests have shown that when I do this: HostSetOrderedIndex &oi = s.get<0>(); oi.insert(p2); HostSetRandomIndex &hsri = s.get<1>(); hsri.sort(); and then iterate over the container (hsri) the order will vary. Sometimes one of the hosts appears at [0] sometimes the other. I'm quite puzzled how this is supposed to work. Can you give me some hints?? Thanks a lot, Stephan PS: I know, the use case is kinda weird. Basically, I want to be able to insert elements with the set logic, and only the IP shall count as identity. Access via random access index is necessary to do hashing in a stable deterministic way over the container.