Question

我想创建一个类数组并打印它。

现在我的方法是：

创建两个不同的类
使用聚合
使用函数创建其中一个类
使用函数打印该数组
所有功能必须为void

这是我到目前为止所拥有的：

#include <iostream>
#include <string>

using namespace std;
const int invsize = 5;

//first class:
class Item {
    private:
        //i'm supposed to have all values set to private
        string itname;
        int itpower;
        int itlasting;
    public:
        //this is so I can create an array of those classes later:
        Item(string i, int j, int k) { itname = i; itpower = j; itlasting = k; }
        //a method to print this class:
        void itprint() {cout << itname << itpower << itlasting;};
        ~Item(){};
};

//second class:
class Player {
    private:
        string plname;
        int plrole;
        int plbrain;
        int plbrawn;
        //aggregation:
        Item * Inventory;
    public:
        void plprint();
        Player();
        ~Player();
};

//a Player constructor, in which I want to create the array of "Items" also:
Player::Player() {

    /*I'm adding info to the Player class first, it works fine and is irrelevant to my question so I didn't paste it here*/

    //now I'm creating an array of Item classes and giving them values:
    Item Inventory[4] = { Item("generic name", 5, 5), Item("generic name", 5, 5), 
               Item("generic name", 5, 5), Item("generic name", 5, 5) };    
}

//a method to print the Player class and the "Inventory" array:
void Player::plprint() {

    /*printing the info about the Player class here first, again, works fine and is irrelevant so I didn't copypaste it*/

    //printing the "Inventory" array:
    cout << "Your inventory contains:" << endl;
    for (int i=1;i<invsize;i++) {
        Inventory[i].itprint();
    }
}

//and finally the main:
int main () {

    //creating a Player class - as I understand, the "Inventory" array should get created with it   
    Player * firstPlayer = new Player;
    //printing the created object and its inventory
    firstPlayer->plprint();

    system("pause");
    return 0;
}

程序编译，当我运行它时，它似乎正确地创建了Player类，它还打印了关于播放器的信息就好了，然后数组出了问题，整个事情就崩溃了。

我确定我在这里无法理解。我非常感谢任何帮助。我google了很多，但无法找到任何相关的教程或回答问题。先感谢您！原谅我的英语不好，这是我的第二语言。

Answer 1

似乎正确创建了Player类

不，它没有。

Player::Player() {

/*I'm adding info to the Player class first, it works fine and is irrelevant to my question so I didn't paste it here*/

//now I'm creating an array of Item classes and giving them values:
Item Inventory[4] = { Item("generic name", 5, 5), Item("generic name", 5, 5), 
           Item("generic name", 5, 5), Item("generic name", 5, 5) };

}

您正在Player构造函数中创建一个名为Inventory的Item数组，这是一个局部变量，而不是指您的成员变量Inventory。

因此，当你的构造函数结束时，本地数组Inventory将被销毁......

那么，为什么要使用指针作为库存数组呢？您可以通过使用数组本身轻松完成此操作。

然后数组出现问题，整个事情就崩溃了。

void Player::plprint() {

/*printing the info about the Player class here first, again, works fine and is irrelevant so I didn't copypaste it*/

//printing the "Inventory" array:
cout << "Your inventory contains:" << endl;
for (int i=1;i<invsize;i++) {
    Inventory[i].itprint();
}

}

这是因为你正在计算并从1开始打印数组，数组应该从0开始。所以你应该使用for (int i = 0; i < invsize - 1; ++i) {/*...*/} 重要的是，在C ++或几乎所有编程语言中，数组从0开始

您缺少类Item的默认构造函数，因此如果您在尝试声明Item Inventory或Item Inventory时会出现错误[4]

固定代码：

#include <iostream>
#include <string>

using namespace std;
const int invsize = 5;

//first class:
class Item {
private:
    //i'm supposed to have all values set to private
    string itname;
    int itpower;
    int itlasting;
public:
    //this is so I can create an array of those classes later:
    Item() {};
    Item(string i, int j, int k) { itname = i; itpower = j; itlasting = k; }
    //a method to print this class:
    void itprint() { cout << itname << " " << itpower << " " << itlasting << std::endl; };
    ~Item() {};
};

//second class:
class Player {
private:
    string plname;
    int plrole;
    int plbrain;
    int plbrawn;
    //aggregation:
    Item Inventory [4];
public:
    void plprint();
    Player();
    ~Player();
};

//a Player constructor, in which I want to create the array of "Items" also:
Player::Player() {

    /*I'm adding info to the Player class first, it works fine and is irrelevant to my question so I didn't paste it here*/

    //now I'm creating an array of Item classes and giving them values:
    for (int i = 0; i < 4; ++i)
    {
        Inventory[i] = Item("generic name", 5, 5);
    }
};

//a method to print the Player class and the "Inventory" array:
void Player::plprint() {

    /*printing the info about the Player class here first, again, works fine and is irrelevant so I didn't copypaste it*/

    //printing the "Inventory" array:
    cout << "Your inventory contains:" << endl;
    for (int i = 0; i<invsize - 1; i++) {
        Inventory[i].itprint();
    }
}

//and finally the main:
int main() {

    //creating a Player class - as I understand, the "Inventory" array should get created with it   
    Player * firstPlayer = new Player;
    //printing the created object and its inventory
    firstPlayer->plprint();

    system("pause");
    return 0;
}

C ++创建一个类数组并打印它

1 个答案: