class a
{
   private:
      string attribute;
      string p_msg;
   public:
      string& getAttribute()
      {
         return attribute;
      }
};

void sortFile(Manager& manage, const char* file)
{
   string text, Id;
   text = file;
   Id = text.substr (0, 2);
   
   a* aa; //i'm trying to make object of class a >.<

   aa.getAttribute() = Id; //this line doesn't work, I'm trying to assign      
                                         attribute from getAttribute() to var Id.
}

aa a;
a.getAttribute();

 aa.getAttribute() = Id;

Id = aa->getAttribute();

class thing {
private:
  std::string str;
 
public:
  thing(std::string _str) 
    : str(_str) {
  }
  std::string &getAttribute() {
    return str;
  }
};
int main(int argc, char* argv[]) {
  thing inst("one");
  std::cout<< inst.getAttribute() << "\n";
 
  inst.getAttribute() = "two";
  std::cout<< inst.getAttribute() << "\n";
 
  thing *ptr = &inst;
  ptr->getAttribute() = "three";
  std::cout<< inst.getAttribute() << "\n";
 
  return 0;
}

a* aa = new a();
 
aa->GetAttribute() = Id;

a aa;
 
aa.GetAttribute() = Id;