如何让一个类的向量从其他两个类的向量中推回数据？

Question

给定 A、B 和 C 类，我想知道如何将属于 A 类和 B 类的向量的分量推回属于 class C 的向量。

例如，在下面的代码中，我有一个用于订购比萨饼的简单程序。 该程序允许用户在系统中输入新客户和新的比萨饼类型，然后程序使用这些数据将客户和比萨饼向量推回。

neworder() function 要求用户输入将构成订单的客户和披萨的 ID 号。 然后程序搜索这些 ID 号，如果匹配，它会要求用户确认这些 ID 代表正确的客户和披萨。

一旦用户确认订单正确，我想推回 Order 类的订单向量，以包含与用户提供的 ID 相对应的比萨饼向量和客户向量的组件。

例如，如果用户输入 ID 0 0 并确认这是正确的选择，我希望程序使用存储在 x.pizzas[0] (0, "wheat", " amatriciana"、"provolone"、"squid")以及存储在 y.customers[0] {0, "Bjarne", "Stroustrup"} 中的信息。 （请注意，ID 编号对应于矢量位置。）

最好的方法是什么？ 一如既往地感谢您的帮助！

//Test to see how I can get a vector in one class to store elements from vectors from two other classes

using namespace std;
#include <iostream>
#include <vector>

class Pizza
{
public:
    string crust;
    string sauce;
    //Mmm... string cheese
    string cheese;
    string topping;
    int pizzaid;
    vector<Pizza> pizzas;
    void addtomenu();

    Pizza(int a, string b, string c, string d, string e)
        : pizzaid{a}, crust{b}, sauce{c}, cheese{d}, topping{e} {}
};

class Customer
{
public:
    string firstname;
    string lastname;
    int customerid;
    vector<Customer> customers;
    void addcustomer();
    Customer(int a, string b, string c)
        : customerid{a}, firstname{b}, lastname{c} {}
};

class Order
{
public:
    Pizza orderedpizza;
    Customer customerordering;
    int orderid;
    vector<Order> orders;
    void neworder();
    void data();
    Order(Pizza a, Customer b)
        : orderedpizza{a}, customerordering{b} {}
};

//I added in these placeholder objects so that I could run functions/push back vectors that belong to these functions' classes. I'm not sure whether there is a more sophisticated way to do this.
//I used negative integers just in case positive ones would interfere with actual pizza/customer IDs.
Pizza x{-1, " ", " ", " ", " "};
Customer y{-1, " ", " "};
Order z{x, y};

void Pizza::addtomenu()
{
    cout << "Please enter the crust, sauce, cheese, and topping that this pizza will have, all separated by spaces.\n";
    cin >> crust >> sauce >> cheese >> topping;
    pizzaid = pizzas.size();
    x.pizzas.push_back(Pizza{pizzaid, crust, sauce, cheese, topping});
    cout << "The pizza has been added.\n";
}

void Customer::addcustomer()
{
    cout << "Please enter the first and last name of the customer, separated by spaces.\n";
    cin >> firstname >> lastname;
    customerid = customers.size();
    y.customers.push_back(Customer{customerid, firstname, lastname});
    cout << "The customer has been added.\n";
}

void Order::neworder()
{
    int tempcustomerid;
    int temppizzaid;
    bool trueflag1 = 0;
    bool trueflag2 = 0;
    string entry;
    cout << "Please enter the customer's ID, followed by the ID of the pizza being ordered. Separate the two with spaces.\n";
    if (cin >> tempcustomerid >> temppizzaid)
    {
        for (int d = 0; d < y.customers.size(); d++)
        {
            if (tempcustomerid == y.customers[d].customerid)
            {
                trueflag1 = 1;
                tempcustomerid = d;
            }
        }

        if (trueflag1 == 0)
        {
            cin.clear();
            cin.ignore(1000, '\n');
            cout << "That ID does not match any customer in the system.\n";
            return;
        }

        for (int e = 0; e < x.pizzas.size(); e++)
        {
            if (temppizzaid == x.pizzas[e].pizzaid)
            {
                cin.clear();
                cin.ignore(1000, '\n');
                trueflag2 = 1;
                temppizzaid = e;
            }
        }

        if (trueflag2 == 0)
        {
            cout << "That ID does not match any pizza in the system.\n";
            return;
        }

        {
            cout << "The following customer: " << y.customers[tempcustomerid].customerid << " " << y.customers[tempcustomerid].firstname << " " << y.customers[tempcustomerid].lastname << " ";
            cout << "will be ordering the following pizza: " << x.pizzas[temppizzaid].pizzaid << " " << x.pizzas[temppizzaid].crust << " " << x.pizzas[temppizzaid].sauce << " " << x.pizzas[temppizzaid].cheese << " " << x.pizzas[temppizzaid].topping << ".\n";
            cout << "Is that correct? If yes, press 1; if no, press 0.\n";
            cin >> entry;
            if (entry == "1")
            {
                //Here, I would like to push back my orders vector to include the contents of y.customers[tempcustomerid] and y.pizzas[temppizaid]. What would be the best way to do this?

                cout << "The order has been placed.\n";
            }
            else
            {
                cout << "Order canceled.\n";
                return;
            }
        }
    }
    else
    {
        cin.clear();
        cin.ignore(10000, '\n');
        cout << "Please enter your input in integer form.\n";
    }
}

void Order::data()
{
    cout << "Pizzas entered into system so far:\n";
    for (int d = 0; d < x.pizzas.size(); d++)
    {
        cout << x.pizzas[d].pizzaid << " " << x.pizzas[d].crust << " " << x.pizzas[d].sauce << " " << x.pizzas[d].cheese << " " << x.pizzas[d].topping << "\n";
    }

    cout << "Customers entered into system so far:\n";
    for (int d = 0; d < y.customers.size(); d++)
    {
        cout << y.customers[d].customerid << " " << y.customers[d].firstname << " " << y.customers[d].lastname << "\n";
    }
}

int main()

{
    //These two push_back functions are added to create test items for debugging purposes.
    x.pizzas.push_back(Pizza{0, "wheat", "amatriciana", "provolone", "squid"});
    y.customers.push_back(Customer{0, "Bjarne", "Stroustrup"});

    string entry;
    while (true)
    {
        cout << "Welcome to the Pizza Orderer 5000. To enter a new customer, enter addcustomer. To enter a new pizza to the menu, enter addtomenu. To enter a new order, enter order. To list all data in the system, enter data. To quit, enter quit.\n";
        cin >> entry;
        if (entry == "addcustomer")
            y.addcustomer();
        else if (entry == "addtomenu")
            x.addtomenu();
        else if (entry == "order")
            z.neworder();
        else if (entry == "data")
            z.data();
        else if (entry == "quit")
            break;
        else
        {
            cin.clear();
            cin.ignore(10000, '\n');
            cout << "I'm sorry, that input was not recognized. Please try again.\n";
        }
    }
}

Answer 1

PaulMckenzie 的评论启发我解决了这个问题，方法是使用每个订单的 customerid 和 Pizzaid 的（副本）而不是 Pizza 和 Customer 类本身来推回订单向量。 然后可以使用订单向量中的信息来重现来自比萨饼和顾客向量的信息。

我没有将 Pizzas 的 int Pizzaid 和 Customer 的 int customerid 包含为 Order class 的成员，而是复制了它们。 我想会有一种方法可以使用原始整数（如果是这样，请告诉我）。

这是修改后的代码，还有一些额外的注释：

using namespace std;
#include <iostream>
#include <vector>

class Pizza
{
public:
    string crust;
    string sauce;
    //Mmm... string cheese
    string cheese;
    string topping;
    int pizzaid;
    vector<Pizza> pizzas;
    void addtomenu();

    Pizza(int a, string b, string c, string d, string e)
        : pizzaid{a}, crust{b}, sauce{c}, cheese{d}, topping{e} {}
};

class Customer
{
public:
    string firstname;
    string lastname;
    int customerid;
    vector<Customer> customers;
    void addcustomer();
    Customer(int a, string b, string c)
        : customerid{a}, firstname{b}, lastname{c} {}
};

class Order
{
public:
    int orderedpizzaid;
    int orderingcustomerid;
    int orderid;
    vector<Order> orders;
    void neworder();
    void data();
    Order (int a, int b, int c) 
    : orderid{a}, orderingcustomerid{b}, orderedpizzaid{c} {}
};

//I added in these placeholder objects so that I could run functions/push back vectors that belong to these functions' classes. I'm not sure whether there is a more sophisticated way to do this.
//I used negative integers just in case positive ones would interfere with actual pizza/customer IDs.
Pizza x{-1, " ", " ", " ", " "};
Customer y{-1, " ", " "};
Order z{-1, -1, -1};

void Pizza::addtomenu()
{
    cout << "Please enter the crust, sauce, cheese, and topping that this pizza will have, all separated by spaces.\n";
    cin >> crust >> sauce >> cheese >> topping;
    pizzaid = pizzas.size();
    x.pizzas.push_back(Pizza{pizzaid, crust, sauce, cheese, topping});
    cout << "The pizza has been added.\n";
}

void Customer::addcustomer()
{
    cout << "Please enter the first and last name of the customer, separated by spaces.\n";
    cin >> firstname >> lastname;
    customerid = customers.size();
    y.customers.push_back(Customer{customerid, firstname, lastname});
    cout << "The customer has been added.\n";
}

void Order::neworder()
{
    int orderid;
    int orderedpizzaid;
    int orderingcustomerid;
    bool trueflag1 = 0;
    bool trueflag2 = 0;
    string entry;
    cout << "Please enter the customer's ID, followed by the ID of the pizza being ordered. Separate the two with spaces.\n";
    if (cin >> orderingcustomerid >> orderedpizzaid)
    {
        for (int d = 0; d < y.customers.size(); d++)
        {
            if (orderingcustomerid == y.customers[d].customerid)
            {
                trueflag1 = 1;
                orderingcustomerid = d;
            }
        }

        if (trueflag1 == 0)
        {
            cin.clear();
            cin.ignore(1000, '\n');
            cout << "That ID does not match any customer in the system.\n";
            return;
        }

        for (int e = 0; e < x.pizzas.size(); e++)
        {
            if (orderedpizzaid == x.pizzas[e].pizzaid)
            {
                cin.clear();
                cin.ignore(1000, '\n');
                trueflag2 = 1;
                orderedpizzaid = e;
            }
        }

        if (trueflag2 == 0)
        {
            cout << "That ID does not match any pizza in the system.\n";
            return;
        }

        {
            cout << "The following customer: " << y.customers[orderingcustomerid].customerid << " " << y.customers[orderingcustomerid].firstname << " " << y.customers[orderingcustomerid].lastname << " ";
            cout << "will be ordering the following pizza: " << x.pizzas[orderedpizzaid].pizzaid << " " << x.pizzas[orderedpizzaid].crust << " " << x.pizzas[orderedpizzaid].sauce << " " << x.pizzas[orderedpizzaid].cheese << " " << x.pizzas[orderedpizzaid].topping << ".\n";
            cout << "Is that correct? If yes, press 1; if no, press 0.\n";
            cin >> entry;
            if (entry == "1")
            {orderid = orders.size();
            //The orders ID is pushed back with only the order ID and (copies of)
//the pizza and customer IDs. However, this information will be sufficient to 
//reproduce all of the customer and pizza information that corresponds to the 
//customer and pizza IDs, as shown in the data function. 
               z.orders.push_back(Order{orderid, orderingcustomerid, orderedpizzaid});
                cout << "The order has been placed.\n";
            }
            else
            {
                cout << "Order canceled.\n";
                return;
            }
        }
    }
    else
    {
        cin.clear();
        cin.ignore(10000, '\n');
        cout << "Please enter your input in integer form.\n";
    }
}

void Order::data()
{
    cout << "Pizzas entered into system so far:\n";
    for (int d = 0; d < x.pizzas.size(); d++)
    {
        cout << x.pizzas[d].pizzaid << " " << x.pizzas[d].crust << " " << x.pizzas[d].sauce << " " << x.pizzas[d].cheese << " " << x.pizzas[d].topping << "\n";
    }

    cout << "Customers entered into system so far:\n";
    for (int d = 0; d < y.customers.size(); d++)
    {
        cout << y.customers[d].customerid << " " << y.customers[d].firstname << " " << y.customers[d].lastname << "\n";
    }

cout << "Orders entered into system so far:\n";
for (int d = 0; d < z.orders.size(); d++)
    {
        //Each order is given an order ID that equals that order's position in the 
//orders vector. The orders vector stores both each order's ID and copies of the IDs
//of the pizza and customer that were included in that order.
        //Therefore, for each order in the orders vector, the following code: (1) prints
// the corresponding order id; (2) prints information from the customers vector for the 
//customer whose customerid matches the orders vector's orderingcustomerid; and (3) prints
// information from the pizzas vector for the pizza whose pizzaid matches the orders 
//vector's orderingpizzaid.
        cout << "Order ID: " << z.orders[d].orderid; 
        cout << " Customer information: " <<  y.customers[z.orders[d].orderingcustomerid].customerid << " " << y.customers[z.orders[d].orderingcustomerid].firstname << " " << y.customers[z.orders[d].orderingcustomerid].lastname;
        cout << " Pizza information: " << x.pizzas[z.orders[d].orderedpizzaid].pizzaid << " " << x.pizzas[z.orders[d].orderedpizzaid].crust << " " << x.pizzas[z.orders[d].orderedpizzaid].sauce << " " << x.pizzas[z.orders[d].orderedpizzaid].cheese << " " << x.pizzas[z.orders[d].orderedpizzaid].topping << "\n";
    }

}

int main()

{
    //These two push_back functions are added to create test items for debugging purposes.
    x.pizzas.push_back(Pizza{0, "wheat", "amatriciana", "provolone", "squid"});
    y.customers.push_back(Customer{0, "Bjarne", "Stroustrup"});

    string entry;
    while (true)
    {
        cout << "Welcome to the Pizza Orderer 5000. To enter a new customer, enter addcustomer. To enter a new pizza to the menu, enter addtomenu. To enter a new order, enter order. To list all data in the system, enter data. To quit, enter quit.\n";
        cin >> entry;
        if (entry == "addcustomer")
            y.addcustomer();
        else if (entry == "addtomenu")
            x.addtomenu();
        else if (entry == "order")
            z.neworder();
        else if (entry == "data")
            z.data();
        else if (entry == "quit")
            break;
        else
        {
            cin.clear();
            cin.ignore(10000, '\n');
            cout << "I'm sorry, that input was not recognized. Please try again.\n";
        }
    }
}