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Can you create a std::map of inherited classes?

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醉梦人生
醉梦人生 2021-01-14 12:14

I\'m wondering if it\'s possible to create a map of pointers of inherited classes. Here\'s an example of what I\'m trying to do:

#include 
#inc
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  • 一生所求
    一生所求 (楼主)
    2021-01-14 12:48

    First things first:

    template
map m;

    This is not valid C++ and could only mean something like a template alias, but I believe, that is not what you are looking for.

    Storing polymorphic objects in C++ is complicated by slicing (constructing a value of the base type from a value of a derived type). Dynamic polymorphism can only be handled through references or pointers. You could potentially use std::ref or boost::ref for situations in which the map will only be passed down the callstack, but this requires some care. Often, storing pointers to the base is the way to go: std::map. Managing deallocation yourself is rather tedious and either std::map or std::map are preferred, depending if you need shared semantics or not.

    Basic example. Someone should replace this with something more meaningful.

    #include 
#include 
#include 
#include 

class animal
{
public:
  virtual ~animal() {};
  virtual void make_sound() const = 0;
};

class dog : public animal
{
public:
  void make_sound() const { std::cout << "bark" << std::endl; }
};
class bird : public animal
{
public:
  void make_sound() const { std::cout << "chirp" << std::endl; }
};

int main()
{
  std::map> m;
  m.insert(std::make_pair("stupid_dog_name", new dog));
  m.insert(std::make_pair("stupid_bird_name", new bird));
  m["stupid_dog_name"]->make_sound();
  return 0;
}

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