C ++在单例中传递指针-然后程序停止工作了？

Question

所以我尝试开发一个 class 记分板和一个 class 玩家和一个 class Player2（所有单例）并且每个游戏都应该有一个指向这个记分板的指针。当我运行我的程序停止工作时，我相信这是因为指针，因为它发生在我试图访问玩家指向的记分牌时。所以基本思想是： (header.h)

    #include <iostream>
    #include <fstream>
    #include <sstream>
    #include <string>
    using namespace std;

    class Scoreboard
    {
    private:
        static Scoreboard *instance;
    Scoreboard()
    {
        p1=0;
        p2=0;
        num=0;
        board[0]="a";       
    };
    public :
    int p1;
    int p2;
    int num;
    string board[9];
    static Scoreboard *startGame()
    {
        if (NULL==instance)
        {
        instance = new Scoreboard();
        }
        return instance ;
    };  
    void printScore()
    {
        cout<<"X "<<p1<<endl;
        cout<<"O "<<p2<<endl;
    }
    void makeMove(string move)
    {
        cout<<move<<endl;
        cout<<p1<<endl;
        board[num]=move;
        cout<<"(plays"<<move<<")"<<endl;
        num++;
    }

    };
    Scoreboard* Scoreboard::instance=NULL;
    class Player
    {
    private :
    static Player *instance;
    Player(char n2,string f2,Scoreboard *sb2)
    {
        name=n2;
        fileName=f2;
        op.open(fileName.c_str());
        s=sb2;
    }
    public:
    string fileName;
    char name;
    string move;
    ifstream op;
    Scoreboard *s;
    static Player *ins(char n,string f,Scoreboard *sb)
    {
        if (NULL==instance)
        {
            instance=new Player(n,f,sb);
        }
        return instance;
    }
    int makeMove()
    {
        cout<<name<<"'s move"<<endl;
        if (!op.eof())
        {
            if (op.is_open())
            {
                cout<<"successfully opened"<<endl;
            }
        op>>move;
        cout<<"successfully got value"<<endl;
        s->makeMove(move);
        return 1;
        }else
        {
            return 0;
        }
    }

    };
    Player* Player::instance=NULL;




    class Player2
    {
    private :
    static Player2 *instance2;
    Player2(char n2,string f2,Scoreboard *sb2)
    {
        name=n2;
        fileName=f2;
        op.open(fileName.c_str());
        s=sb2;
    }
    public:
    string fileName;
    char name;
    string move;
    ifstream op;
    Scoreboard *s;

    static Player2 *ins(char n,string f,Scoreboard *sb)
    {
        if (NULL==instance2)
        {
            instance2=new Player2(n,f,sb);
        }
        return instance2;
    }
    int makeMove()
    {
        cout<<name<<"'s move"<<endl;
        if (!op.eof())
        {
            if (op.is_open())
            {
                cout<<"successfully opened"<<endl;
            }
        op>>move;
        cout<<"successfully got value"<<endl;

        s->makeMove(move);

        return 1;
        }else
        {
            return 0;
        }
    }

    };
    Player2* Player2::instance2=NULL;

.cpp 将是：

    #include "stdafx.h"
    #include "header.h"

    int main(int argc, char* argv[])
    {
    string store;
    string temp;
    string temp2;
    getline(cin,store);
    istringstream stm(store);
    stm>>temp;
    Scoreboard* si=NULL;
    Player* ply1=NULL;
    Player2* ply2=NULL;

    if (temp=="game")
    {
        Scoreboard* si= Scoreboard::startGame();
        cout<<si->p1<<endl;
        cout<<si->p2<<endl;
        cout<<si->board[0]<<endl;


    }
    stm>>temp;
    stm>>temp2;

    if (temp=="stdin"&&temp2=="stdin")
    {

    }else
    {
        ply1=Player::ins('X',temp,si);
        ply2=Player2::ins('O',temp2,si);
        cout<<ply1->s->p1<<endl;
    -----------------------------------------------------
     //This is where program stop working(I think)
    -----------------------------------------------------


    }

    while(1)
    {
        ply1->makeMove();
        ply2->makeMove();
    }
    for(int i=0;i<9;i++)
    {
        cout<<si->board[i]<<" ";
    }

    }

Answer 1

我看到的一个问题是：

 if (temp=="game")
 {
   Scoreboard* si= Scoreboard::startGame();`  
   //...
 }

si是局部变量，所以在}之外就不存在了。上面的 si 与您之前在 main 中声明的 si 不同：

Scoreboard* si=NULL;

因此您在此处取消引用 NULL 指针，因为 "real" si 从未设置：

cout<<si->board[i]<<" ";

C ++在单例中传递指针-然后程序停止工作了？

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