c++11 - C++ get the first argument value in template parameter pack -


i have class

class assetmanager { private:     std::unordered_map<const std::type_info*, asset*> assets;  public:     assetmanager();     virtual ~assetmanager();      template <typename t, typename ...args>     bool newasset(args... args)     {            //get path         if(cached(path)) { return true; }          auto asset = new t{ std::forward<args>(args)... };         assets[&typeid(*asset)] = asset;         return *static_cast<t*>(assets[&typeid(t)]);     }      bool cached(const std::string& path)     {         for(auto asset : assets) {           if(asset.second->getpath() == path) {              return true;           }         }          return false;     } };

the first argument of every asset std::string path. i'm trying value , see if it's loaded in list. asset abstract class. 

class asset { private:     std::string path;  public:     asset(const std::string& path);     virtual ~asset() = default;     virtual bool load() = 0;     std::string getpath(); };

classes inheriting asset may have different number of arguments , such i'm trying capture value of first argument because std::string path can see in asset class constructor.

if first argument std::string, makes lot of sense declare way. 1 thing, solves problem. another, ensures callers can never wrong. , if need in constructor of asset well, either pass separately constructor or declare there well.

template <typename t, typename ...args> bool newasset(const std::string &path, args&&... args) {        //get path     if(cached(path)) { return true; }      auto asset = new t{ path, std::forward<args>(args)... };     assets[&typeid(*asset)] = asset;     return *static_cast<t*>(assets[&typeid(t)]); }

i'm wondering use of typeid; absolutely using key in map correct? don't see operator<, , operator== not guaranteed give consistent results according http://en.cppreference.com/w/cpp/language/typeid (under 'notes'). might better use typeid.hash_code() instead.


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