c++ - Template base type inheritance -

i have following classes:

class box{...}; class mybox : public box{...}; 

and template:

template <type t> class objectmanager{...}; 

which use in other class:

class engine{     objectmanager<box> * manager = nullptr;     ... }; 

then extend (implement) engine interface:

class myengine : public engine{...} 

and in implementation (not earlier!) know manager should that:

myengine::myengine(){     manager = new objectmanager<mybox>(); } 

but gives me error because of types conflict (conversion between objectmanager<box> , objectmanager<mybox>), when mybox inherits box.

is there way around problem? i don't want modify box, mybox, objectmanager , engine classes.

templatize engine , inherit myengine engine carrying template instance of box desire. this: (http://codepad.org/szmsbcrb)

#include <iostream>  using namespace std;  class box{ };  class mybox : public box{ };  template <typename t> class objectmanager{  };  template <typename t> class engine{     public:     objectmanager<t*> * manager; };  class myengine : public engine<mybox>{      public:     myengine(){     manager = new objectmanager<mybox*>();     cout<<"myengine created"<<endl;     } };  int main() {      myengine eng = myengine();        return 0;  } 

the benefit here is, if tomorrow create new box namely mybox2 , want create custom engine myengine2 well, inherit myengine : public engine <mybox2>. make sure take care of type conversions.

as far remember, in java can declare engine engine<extends t> lets instantiate engine subtype of template t provided. safer , better way it, not know if c++ provides that.

hope helps.