Boost multi_index composite keys using MEM_FUN

问题:

Is there a way to use member functions in the specification of composite_key's in boost multi_index_container's?

#include <boost/multi_index_container.hpp> #include <boost/multi_index/mem_fun.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/composite_key.hpp> #include <boost/multi_index/member.hpp> #include <iostream> #include <string>  using namespace boost::multi_index; using namespace std;  class Name { public:     Name(const string &first, const string &middle, const string &last) : m_first(first) , m_middle(middle) , m_last(last) {}      friend std::ostream& operator << (ostream& os,const Name& n)    {         os << n.m_first << " " << n.m_middle << " " << n.m_last << endl;         return os;     }      const string &first() const { return m_first; }     const string &middle() const { return m_middle; }     const string &last() const { return m_last; } private:     string m_first, m_middle, m_last; };  struct first {}; struct middle {}; struct last {}; struct last_first {};   typedef multi_index_container <     Name,      indexed_by<         ordered_non_unique<tag<first>, BOOST_MULTI_INDEX_CONST_MEM_FUN( Name, const string &, first)         >,         ordered_non_unique<tag<middle>, BOOST_MULTI_INDEX_CONST_MEM_FUN(Name, const string &, middle)         >,         ordered_non_unique<tag<last>, BOOST_MULTI_INDEX_CONST_MEM_FUN(Name, const string &, last)         >,         ordered_non_unique<              composite_key<                 Name,                 member<tag<last>, BOOST_MULTI_INDEX_CONST_MEM_FUN(Name, const string &, last)>,                 member<tag<first>, BOOST_MULTI_INDEX_CONST_MEM_FUN( Name, const string &, first)>             >         >     > > Name_set;  typedef Name_set::index<first>::type Name_set_by_first; typedef Name_set::index<middle>::type Name_set_by_middle; typedef Name_set::index<last>::type Name_set_by_last;  void main() {      Name_set names;     names.insert(Name("robert", "shawn", "mitchell"));     names.insert(Name("ravi", "john", "spaceman"));     names.insert(Name("david", "abel", "mccoy"));     names.insert(Name("steven", "xavier", "anser"));     names.insert(Name("kris", "nomiddlename", "spigha"));     names.insert(Name("jina", "wilson", "fabrice"));     names.insert(Name("zebbo", "aniston", "michaels"));     names.insert(Name("antonio", "magician", "esfandiari"));     names.insert(Name("nora", "iris", "mitchell"));      cout << "SORTED BY FIRST NAME" << endl;     for (Name_set_by_first::iterator itf = names.get<first>().begin(); itf != names.get<first>().end(); ++itf)         cout << *itf;      cout << "SORTED BY MIDDLE NAME" << endl;     for (Name_set_by_middle::iterator itm = names.get<middle>().begin(); itm != names.get<middle>().end(); ++itm)         cout << *itm;      cout << "SORTED BY LAST NAME" << endl;     for (Name_set_by_last::iterator itl = names.get<last>().begin(); itl != names.get<last>().end(); ++itl)         cout << *itl;      Name_set_by_last::iterator mitchells = names.get<last>().find("mitchell");     while (mitchells->last() == "mitchell")         cout << *mitchells++;  } 

The code above represents what I would like to do, but the member<> template does not accept the BOOST_MULTI_INDEX_CONST_MEM_FUN macro the way ordered_non_unique<> does.

Anyone come across this?

Thanks!

回答1:

It looks like you're trying to tag the key extractors in the composite case, but I think you can only tag indexes. I think what you want is to replace

    ordered_non_unique<          composite_key<             Name,             member<tag<last>, BOOST_MULTI_INDEX_CONST_MEM_FUN(Name, const string &, last)>,             member<tag<first>, BOOST_MULTI_INDEX_CONST_MEM_FUN( Name, const string &, first)>         >     > 

with

    ordered_non_unique< tag<somenewtagtype>         composite_key<             Name,             BOOST_MULTI_INDEX_CONST_MEM_FUN(Name, const string &, last),             BOOST_MULTI_INDEX_CONST_MEM_FUN(Name, const string &, first)         >     > 

文章来源: Boost multi_index composite keys using MEM_FUN