c++ - 制作一个抽象类类型的集合，shared_ptr的抽象类 vector

Question

错误

e/c++/v1/algorithm:642: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/utility:321:9: error:

field type 'Space' is an abstract class _T2 second; ^

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/map:624:16: note:

问题

如何定义 std::vector类型 Space这是一个抽象类，然后用派生类的实例填充这个 vector Empty , Snake , Ladder .

上下文

我知道 C++ 中的抽象类不能被实例化。相反，我在这个网站和其他网站上的几篇文章中读到，如果类型定义为星号，您可以创建抽象类型的集合 *指针或任何 <memory>托管指针数据类型，如 std::unqiue_ptr<T> .我试过使用 shared_ptr<Space>就我而言，但仍然无法正确定义集合。我使用 g++ -std=c++17 main.cpp && ./a.out 编译了我的代码.

代码

#include <cstdlib>
#include <cmath>
#include <iostream>
#include <map>
#include <memory>
#include <typeinfo>
#include <queue>
#include <string>
#include <vector>

class Player
{
    private:
        int m_current_space = 1;
    public:
        Player() {}
        void role_dice() {
            m_current_space += floor( (rand()%10 + 1) / 3 );
        }
        int const get_current_space() {
            return m_current_space;
        }
        void set_current_space(int current_space) {
            m_current_space = current_space;
        }
};

class Space
{
    protected:
        int m_id;
        std::vector<Space> m_paths;
    public:
        Space() {} // requied to use [] operator in map
        Space(int id) : m_id(id) {}
        void add_path(Space& s) {
            m_paths.push_back(s);
        }
        int get_id() {
            return m_id;
        }
        virtual std::string class_type() = 0;
};
class Empty : public Space
{
    public:
        Empty(int id) : Space(id) {}
        std::string class_type() {
            return "Empty";
        }
};
class Ladder : public Space
{
    public:
        Ladder(int id) : Space(id) {}
        virtual void event(Player& p) {
            p.set_current_space(1);
        }
        std::string class_type() {
            return "Ladder";
        }
};
class Snake : public Space
{
    public:
        Snake(int id) : Space(id) {}
        virtual void event(Player& p) {
            p.set_current_space(4);
        }
        std::string class_type() {
            return "Snake";
        }
};

class Board
{
    private:
        std::map<int, Space> m_board;
    public:
        void add_space(Space& s) {
            m_board[s.get_id()] = s;
        }
        void draw_board() {
            int i = 1;
            for(auto const& [space_key, space] : m_board) {
                if(i%3 == 0) {
                    std::cout << "○\n";
                }
                else if(typeid(space) == typeid(Snake)) {
                    std::cout << "○-";
                }
                else {
                    std::cout << "○ ";
                }
                ++i;
            }
        }
        void update_player_on_board(int position) {
            int i = 1;
            for(auto const& [space_key, space] : m_board) {
                if(i%3 == 0) {
                    if (space_key == position) {
                        std::cout << "●\n";
                    }
                    else {
                        std::cout << "○\n";
                    }
                }
                else if(typeid(space) == typeid(Snake)) {
                    std::cout << "○-";
                }
                else {
                    if (space_key == position) {
                        std::cout << "● ";
                    }
                    else {
                        std::cout << "○ ";
                    }
                }
                ++i;
            }
        }
        const std::map<int, Space> get_board() {
            return m_board;
        }
        friend std::ostream &operator<<(std::ostream& os, const Board& b) {
            return os;
        }
};

class GameStateManager
{
    private:
        std::string m_state = "game over";
        bool m_playing = false;
    public:
        std::string const get_state() {
            return m_state;
        }
        void set_state(std::string state) {
            m_state = state;
        }
};

int main()
{
    std::cout << "Welcome to Bowser's 9 board game\n";
    std::cout << "Start? y(yes) n(no)\n";

        GameStateManager game_manager;
        game_manager.set_state("playing");


        auto space1 = std::make_shared<Space>(1);
        auto space2 = std::make_shared<Space>(2);
        auto space3 = std::make_shared<Space>(3);
        auto space4 = std::make_shared<Space>(4);
        auto space5 = std::make_shared<Space>(5);
        auto space6 = std::make_shared<Space>(6);
        auto space7 = std::make_shared<Space>(7);
        auto space8 = std::make_shared<Space>(8);
        auto space9 = std::make_shared<Space>(9);

        std::vector<std::shared_ptr<Space>> v {
            space1, space2, space3,
            space4, space5, space6,
            space7, space8, space9
        };

        Board bowsers_bigbad_laddersnake;
        for(int i = 0; i < 10; ++i) {
            bowsers_bigbad_laddersnake.add_space(*(v[i]));
        }
        bowsers_bigbad_laddersnake.draw_board();

        Player mario;

        int turn = 0;
        while(game_manager.get_state() == "playing") {
            std::cin.get();
            std::cout << "-- Turn " << ++turn << " --" << '\n';
            mario.role_dice();
            bowsers_bigbad_laddersnake.update_player_on_board(mario.get_current_space());
            if (mario.get_current_space() >= 9) {
                game_manager.set_state("game over");
            }
        }

        std::cout << "Thanks a so much for to playing!\nPress any key to continue . . .\n";
        std::cin.get();



    return 0;
}

Answer 1

您似乎已经删除了很多代码以了解此处的详细信息。有Space指针(智能或原始)。实例化您想要的特定空间，用类型为 Space 的指针指向它.示例 std::shared_ptr<Space> pointerToSpace = std::make_shared<Snake> ("I'm a snake");现在，不失一般性，您可以仅使用指向空格的指针打印内容(具体类型)pointerToSpace->class_type() .是的，您可以收集 shared_ptr在容器中。