std :: map,polymorphism和delete

Question

std :: map,polymorphism和delete

Gui*_*i13 4 c++ polymorphism dictionary rtti delete-operator

我有一个问题,使用C++映射来存储指向基类和一些派生类的指针.

让我用一个相当长但很简单的代码来解释:

#include <map>
#include <iostream>

struct foo{ int dummy[4]; };
struct bar{ int additionnal[4]; };

class Base
{
private:
    struct foo *_internal_structure;
public:
    Base() { _internal_structure = new struct foo; }
   ~Base()
   {
        delete _internal_structure;
        std::cout << "Base DTOR\n";
   }
};

class Derived: public Base
{
private:
    struct bar *_additional_structure;
public:
    Derived() { _additional_structure = new struct bar; }
   ~Derived()
   {
        delete _additional_structure;
        std::cout << "Derived DTOR\n";
   }
};


int main(int argc, char *argv[])
{
    std::map<int, Base*> my_map;
    Base *to_add = new Base();
    Derived *derived_to_add = new Derived();
    my_map[1] = to_add;
    my_map[2] = derived_to_add; // works, derived class, but object gets sliced

    /// clear hash map ///
    std::map<int, Base*>::const_iterator iter;
    for(iter = my_map.begin(); iter != my_map.end(); ++iter)
    {
        delete (*iter).second;
    }

    return 0;
}

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