«конверт» с несколькими «письмами»

#include <cstdlib>
#include <iostream>
#include <stdexcept>
#include <vector>

using std::cout;
using std::endl;

enum
{
    FIRE      = 0x01,
    WIND      = 0x02,
    LIGHTNING = 0x04,
    SOIL      = 0x08,
    WATER     = 0x10
};

class Skill     // aka Jutsu =)
{
public:
    // envelope constructor (see below)
    Skill(int _type) throw (std::logic_error);

    // destructor
    virtual ~Skill()
    {
        if (mLetters.size() != 0)
        {
            cout << "~Skill()\t<- envelope destructor" << endl;

            // virtual call in destructor!
            erase();
        }
        else
        {
            cout << "~Skill()\t<- letter destructor" << endl;
        }

        for (size_t i = 0; i < mLetters.size(); i++)
            delete mLetters[i];     // delete Letter for Envelope
                                    // delete 0      for Letter
    }
    
    virtual void cast() const
    {
        for (size_t i = 0; i < mLetters.size(); i++)
            mLetters[i]->cast();
    }

    virtual void show() const
    {
        for (size_t i = 0; i < mLetters.size(); i++)
            mLetters[i]->show();
    }

    virtual void erase()
    {
        for (size_t i = 0; i < mLetters.size(); i++)
            mLetters[i]->erase(); 
    }

protected:
    // letter constructor
    Skill() : mLetters(NULL) { cout << "Skill()\t\t<- letter constructor" << endl; }

private:
    Skill(const Skill &);
    Skill & operator= (Skill &);

    std::vector<Skill*> mLetters;      // vector of pointers to letters
};


class FireSkill : public Skill
{
public:
    ~FireSkill() { cout << "~FireSkill()" << endl; }
    virtual void cast() const { cout << "Katon!" << endl; }
    virtual void show() const { cout << "FireSkill::show()" << endl; }
    virtual void erase() { cout << "FireSkill:erase()" << endl; }
private:
    friend class Skill;
    FireSkill() {}
    FireSkill(const FireSkill &);
    FireSkill & operator=(FireSkill &);
};


class WoodSkill : public Skill
{
public:
    ~WoodSkill() { cout << "~WoodSkill()" << endl; }
    virtual void cast() const { cout << "Mokuton!" << endl; }
    virtual void show() const { cout << "WoodSkill::show()" << endl; }
    virtual void erase() { cout << "WoodSkill::erase()" << endl; }
private:
    friend class Skill;
    WoodSkill() {}
    WoodSkill(const WoodSkill &);
    WoodSkill & operator=(WoodSkill &);
};


Skill::Skill(int _type) throw (std::logic_error)
{
    cout << "Skill(_type)\t<- envelope constructor" << endl;

    switch (_type)
    {
        case FIRE:
            mLetters.push_back(new FireSkill);
            break;

        case SOIL | WATER:
            mLetters.push_back(new WoodSkill);
            break;

        case FIRE | SOIL | WATER:
            mLetters.push_back(new FireSkill);
            mLetters.push_back(new WoodSkill);
            break;

        // ...

        default:
            throw std::logic_error("Incorrect type of element");
    }

    // virtual call in constructor!
    cast();
}


int main()
{
    std::vector<Skill*> skills;

    try
    {
        skills.push_back(new Skill(FIRE));
        skills.push_back(new Skill(SOIL | WATER));
        skills.push_back(new Skill(FIRE | SOIL | WATER));
    }
    catch (std::logic_error le)
    {
        std::cerr << le.what() << endl;
        return EXIT_FAILURE;
    }

    for (size_t i = 0; i < skills.size(); i++)
    {
        skills[i]->show();
        delete skills[i];
    }

    return EXIT_SUCCESS;
}