对象向量抽象函数调用的分段错误

Question

我正在尝试调用类对象的虚函数。该对象位于二维向量中，我确信它存在，因为它打印出我分配给它的“符号”。我有一个抽象基类，我的其他类派生自该类。每当我尝试调用这个函数时，它都会给我一个段错误。

// In my Cave class constructor, I create my 2d array, and make all the elements default constructors of a room which is an 'Empty,' room.
Room r;
                grid = vector<vector<Room> > (width, vector<Room>(width));
                for(int i = 0; i < width; i ++){
                        for(int j = 0; j < width; j++){
                                Room r;
                                grid[i][j] = r;
                        }
                }

//Here is where I set up all of my 'special,' Rooms
Room g('G');
                        Room b('B');
                        Room b2('B');
                        Room p1('P');
                        Room p2('P');
                        Room w('W');

                        this->grid[0][0] = g;
                        this->grid[0][1] = b;
                        this->grid[0][2] = b2;
                        this->grid[0][3] = p1;
                        this->grid[0][4] = p2;
                        this->grid[0][5] = w;

// This is my room class .cpp I have a non default constructor that should make a new Event object of one of the other object
#include <iostream>
#include <vector>
#include <cstdlib>
#include "room.h"
#include "event.h"
#include "gold.h"
#include "wumpus.h"
#include "pit.h"
#include "empty.h"
#include "bats.h"

using namespace std;

        Room::Room(){
                cout << "making room" << endl;
                symbol = ' ';
                Event *e = new Empty;
        }
        Room::Room(char c){
                cout << "Non-defualt" << endl;
                if(c == 'G'){
                        Event *e = new Gold;
                        symbol = 'G';
                }
                else if(c == 'W'){
                        Event *e = new Wumpus;
                        symbol = 'W';
                }
                else if(c == 'P'){
                        Event *e = new Pit;
                        symbol = 'P';
                }
                else if(c == 'B'){
                        Event *e = new Bats;
                        symbol = 'B';
                }

        }
        void Room::sense(){
                cout << this->symbol << endl;
                this->e->percept();
        }
        char Room::get_symbol(){
                return(this->symbol);
        }

// my Room header file
#ifndef ROOM_H
#define ROOM_H

#include <iostream>
#include "event.h"
#include "bats.h"
#include "empty.h"
#include "wumpus.h"
#include "gold.h"
#include "pit.h"

using namespace std;

class Room {
        public:
                Event *e;
                char symbol;
                Room();
                Room(char);
                void sense();
};
#endif

//here is where I call my 'Sense()' function that is apart of my room class
void Cave::nearby(){
                int x = p.spot/width;
                this->grid[(x - 1)][p.spot % width].sense();
                this->grid[(x + 1)][p.spot % width].sense();
                this->grid[x][(p.spot % width) + 1].sense();
                this->grid[x][(p.spot % width) - 1].sense();
        }

// my abstract event header file
#ifndef EVENT_H
#define EVENT_H
#include <iostream>
using namespace std;
class Event {
        public:
                Event();
                virtual void percept() = 0;
                virtual void encounter() = 0;
};
#endif

//my abstract event.cpp
#include <iostream>
#include "event.h"

using namespace std;

        Event::Event(){
                cout << "making event" << endl;
        }

//Finally my header of the different room types, this one is gold. but they are all the exact same outline and stuff
#ifndef GOLD_H
#define GOLD_H

#include <iostream>
#include <string>
#include "event.h"

using namespace std;

class Gold : public Event {
        private:
                string name;
        public:
                Gold();
                void percept();
                void encounter();
};
#endif

//here is my gold.cpp
#include <iostream>
#include <string>
#include "gold.h"
#include "event.h"

using namespace std;

        Gold::Gold(){
                name = "gold";
                cout << "making gold" << endl;
        }
        void Gold::percept(){
                cout << "You see a glimmer nearby..." << endl;
        }
        void Gold::encounter(){
                cout << "encounter" << endl;
        }

它应该打印出“你看到附近有微光”。或任何其他消息，但我收到了段错误。

Answer 1

            if(c == 'G'){
                    Event *e = new Gold;
                    symbol = 'G';
            }

这将创建一个全新的Event *，也称为e，并将其设置为指向new Gold。那不是你想要的。您希望将名为 e 的现有成员设置为指向 new Gold。所以你想要：

            if(c == 'G'){
                    delete e; // don't leak the existing object
                    e = new Gold;
                    symbol = 'G';
            }

你在其他地方也有同样的问题，包括这里：

            Event *e = new Empty;

应该是：

            e = new Empty;

如果您的编译器没有警告您创建新变量以影响现有类成员，请使用更好的编译器或学习如何打开其警告并确保注意它们。