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c++ - 对象成员变量在函数中更新但不持久

问题描述

我对 C++ 和构建一个简单的战舰游戏相当陌生。我有一个函数，通过接收船舶对象的向量来初始化船舶类型和长度。我已经确认类型和船长正在函数内部更新，但更改并没有保留在主函数中。任何帮助将不胜感激。

#include <iostream>
#include <vector>
#include "ships.h"
#include "board.h"
#include "player.h"


using std::vector; 

void initialize_ships(vector<ship> &newFleet)
{
    vector<string> ship_types = { "carrier","battleship","submarine","cruiser","destroyer" };

    for (auto ii = 0; ii != newFleet.size(); ++ii)
    {
        newFleet[ii].type = ship_types[ii];
        newFleet[ii].setLength();
        if (newFleet[ii].type == "carrier")
        {
            std::cout << "Carrier in function has type: " << newFleet[ii].type << std::endl;
        }

    }
}

int main()
{


ship player_carrier, player_battleship, player_submarine, player_cruiser, player_destroyer;
vector<ship> player_fleet = {player_carrier, player_battleship, player_submarine, player_cruiser, player_destroyer };


initialize_ships(player_fleet);
std::cout << "Carrier in main has type: " << player_carrier.type << std::endl;



system("pause");
return 0; 

}

#ifndef  SHIPS_H
#define SHIPS_H

#include <iostream>
#include <string>


using std::string;

struct ship
{
    // ships member variables 
    int len;
    char dir; 
    int health; 
    int row;
    int col;
    char symb;
    string type; 

    void setLength()
    {
        if (type == "carrier")
        {
            len = 5;
        }
        else if (type == "battleship")
        {
            len = 4;
        }
        else if (type == "cruiser")
        {
            len = 3;
        }
        else if (type == "submarine")
        {
            len = 3;
        }
        else if (type == "destroyer")
        {
            len = 2;
        }
        else
        {
            std::cout << "Invalid ship type!" << std::endl;
        }
    }
};

#endif //  SHIPS_H

标签： c++vector

解决方案

意外制作副本是更改“丢失”的常见原因。对于这种特殊情况，您希望在容器中拥有对象并为这些对象命名（就好像它们是类的成员一样），明智的做法是引用容器中的对象：

vector<ship> player_fleet(5);
ship &player_carrier=player_fleet[0],
  &player_battleship=player_fleet[1],
  &player_submarine=player_fleet[2],
  &player_cruiser=player_fleet[3],
  &player_destroyer=player_fleet[4];

小心不要导致vector重新分配，因为这会使您的引用无效。（当然，如果它从不改变大小，ship player_fleet[5];就足够了。）

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