c++ - template meta-programming how to specialize on a collection -

i have following utlsharedipcwrapper template class created access user defined type placed in inter-process memory.

normally class used simple type example:

// construct faultreport - default no faults auto faultwrapper = managed_shm.construct<     utlsharedipcwrapper<uint64_t>>("faultreport")(0); 

and works well, had need use boost shared memory map collection (boost::interprocess::map) template argument) in:

using char_allocator = boost::interprocess::managed_shared_memory::allocator<char>::type; using shm_string = boost::interprocess::basic_string<char, std::char_traits<char>, char_allocator>; using keytype = shm_string; using valuetype = std::pair<const keytype, shm_string>; using shmemallocator = boost::interprocess::allocator<valuetype, boost::interprocess::managed_shared_memory::segment_manager>; using sharedmemorymap = boost::interprocess::map<shm_string, shm_string, std::less<keytype>, shmemallocator>;  ...  // create new shared memory segment 2k size managed_shared_memory managed_shm(open_only, "sharedmemname");  //initialize shared memory stl-compatible allocator shmemallocator alloc(managed_shm.get_segment_manager());  auto psharednvpairs = managed_shm.find<utlsharedipcwrapper<     sharedmemorymap>>("namevaluepairs").first; 

my question how can change template class definition below pass collection::value types's parameters instead of separately reading entire map 1 operation via psharednvpairs->getshareddata() updating temporary map , writing shared memory again via psharednvpairs->setshareddata(*psharednvpairs). know different types not collections , thefore template metaprogramming magic have performed selective enable if etc,., have method added class along lines of

// don't know correct signature here void setshareddatavalue(const t::value_type& rshareddatavalue) {     boost::interprocess::scoped_lock<upgradable_mutex_type> lock(mmutex);     ... not sure here update collection }  template<typename t> struct utlsharedipcwrapper { private:     using upgradable_mutex_type = boost::interprocess::interprocess_upgradable_mutex;      mutable upgradable_mutex_type mmutex;     /*volatile*/ t mshareddata; public:     // explicit constructor used initialize directly existing memory     explicit utlsharedipcwrapper(const t& rinitialvalue)         : mshareddata(rinitialvalue)     {}      t getshareddata() const {         boost::interprocess::sharable_lock<upgradable_mutex_type> lock(mmutex);         return mshareddata;     }      void setshareddata(const t& rshareddata) {         boost::interprocess::scoped_lock<upgradable_mutex_type> lock(mmutex);         // update shared data copy mapped - scoped locked used if exception thrown         // bit lock guard use         this->mshareddata = rshareddata;     } }; 

why not just

// don't know correct signature here void setshareddatavalue(const typename t::value_type& rshareddatavalue)      {     boost::interprocess::scoped_lock<upgradable_mutex_type> lock(mmutex);     mshareddata.insert(rshareddatavalue); }