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c++ - 如何将2个类分成单独的.h文件并正确设置它们

转载 作者：行者123 更新时间：2023-12-02 10:20:55 26 4
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该代码在main中可以正常工作，而没有用于2个类的单独文件，但是当我尝试将它们分开时，出现很多错误，提示‘ItemToPurchase’ was not declared in this scope。我以为是因为我在ItemToPurchase类中使用了ShoppingCart类，但无法识别实现的位置

我在ShoppingCart.h文件中尝试过类似的操作(如下)，但没有任何效果，我不确定是否丢失了其他错误处理的文件。

#ifndef ShoppingCart_h
#define ShoppingCart_h
#ifndef ItemToPurchase_h
#define ItemToPurchase_h

我在下面发布了工作代码

我不确定如何为5个文件 main和4个 .h文件设置文件头

如果有人可以演示如何设置标题，那是理想的选择，我是一名学生，但此时有点迷路了。 
#include <iostream>
#include <vector>
#include <string>
using namespace std;

class ItemToPurchase
{
private:

    string itemName;
    int itemPrice;
    int itemQuantity;
    string itemDescription;

public:

    ItemToPurchase()
    {
        itemName = "";
        itemPrice = 0;
        itemQuantity = 0;
        itemDescription = "none";
    }
    ItemToPurchase(string name, string description, int price, int quantity)
    {
        itemName = name;
        itemDescription = description;
        itemPrice = price;
        itemQuantity = quantity;
    }
    void SetName(string name)
    {
        itemName = name;
    }
    void SetPrice(int price)
    {
        itemPrice = price;
    }
    void SetQuantity(int quantity)
    {
        itemQuantity = quantity;
    }
    string GetName()
    {
        return itemName;
    }
    int GetPrice()
    {
        return itemPrice;
    }
    int GetQuantity()
    {
        return itemQuantity;
    }
    void SetDescription(string description)
    {
        itemDescription = description;
    }
    string GetDescription()
    {
        return itemDescription;
    }
    void PrintItemCost()
    {
        cout << itemName << " " << itemQuantity << " @ $" << itemPrice << " = $" << itemQuantity * itemPrice << endl;
    }
    void PrintItemDescription()
    {
        cout << itemName << ": " << itemDescription << endl;
    }

};


//---------------------------------------------------------------


class ShoppingCart
{

private:

    string customerName;
    string currentDate;
    vector <ItemToPurchase> cartItems;

public:

    ShoppingCart()
    {
        customerName = "none";
        currentDate = "January 1, 2016";
    }
    ShoppingCart(string name, string date)
    {
        customerName = name;
        currentDate = date;
    }
    string GetCustomerName()
    {
        return customerName;
    }
    string GetDate()
    {
        return currentDate;
    }
    void AddItem(ItemToPurchase newItem)
    {
        cartItems.push_back(newItem);
    }
    void RemoveItem(string name)
    {
        bool temp = true;
        for (int i = 0; i < cartItems.size(); i++)
        {
            if (name == cartItems[i].GetName())
            {
                cartItems.erase(cartItems.begin() + i);
                temp = false;
            }
        }
        if (temp == true)
        {
            cout << "Item not found in cart. Nothing removed." << endl << endl;
        }
    else
    {
      cout << endl;
    }
    }
    void ModifyItem(int quantity, string name)
    {
    bool temp = true;
        for (int i = 0; i < cartItems.size(); i++)
        {
            if (name == cartItems[i].GetName())
            {
                cartItems[i].SetQuantity(quantity);
        temp = false;
            }
        }
        if (temp == true)
        {
            cout << "Item not found in cart. Nothing modified." << endl << endl;
        }
    else
    {
      cout << endl;
    }
    }
    int GetNumItemsInCart()
    {
        int total = 0;
        for (int i = 0; i < cartItems.size(); i++)
        {
            total += cartItems[i].GetQuantity();
        }
        return total;
    }
    int GetCostOfCart()
    {
        int total = 0;
        for (int i = 0; i < cartItems.size(); i++)
        {
            total += cartItems[i].GetPrice() * cartItems[i].GetQuantity();
        }
        return total;
    }
    void PrintTotal()
    {
        if (cartItems.size() == 0)
        {
      cout << GetCustomerName() << "'s Shopping Cart - " << GetDate() << endl;
      cout << "Number of Items: 0" << endl << endl;
            cout << "SHOPPING CART IS EMPTY" << endl << endl;
      cout << "Total: $0" << endl << endl;

        }
        else
        {
            cout << customerName << "'s Shopping Cart - " << currentDate << endl;
            cout << "Number of Items: " << GetNumItemsInCart() << endl << endl;
            for (int i = 0; i < cartItems.size(); i++)
            {
                cartItems[i].PrintItemCost();
            }
            cout << endl << "Total: $" << GetCostOfCart() << endl << endl;
        }
    }
    void PrintDescriptions()
    {
        cout << "Item Descriptions" << endl;
        for (int i = 0; i < cartItems.size(); i++)
        {
            cartItems[i].PrintItemDescription();
        }
    cout << endl;
    }

};



int main()
{

    cout << "Enter customer's name:" << endl;
    string name;
    getline(cin, name);

    cout << "Enter today's date:" << endl << endl;
    string date;
    getline(cin, date);


    cout << "Customer name: " << name << endl;
    cout << "Today's date: " << date << endl << endl;

    ShoppingCart customer(name, date);

    bool on = true;
    bool check = true;
    string select;


    while (on)
    {

        cout << "MENU" << endl;
        cout << "a - Add item to cart" << endl;
        cout << "d - Remove item from cart" << endl;
        cout << "c - Change item quantity" << endl;
        cout << "i - Output items' descriptions" << endl;
        cout << "o - Output shopping cart" << endl;
        cout << "q - Quit" << endl << endl;
        cout << "Choose an option:" << endl;
        cin >> select;

        while (check)
        {
            if (select == "a" || select == "d" || select == "c" || select == "i" || select == "o" || select == "q")
            {
                check = false;
            }
            else
            {
                cout << "Choose an option:" << endl;
                cin >> select;
            }
        }
        check = true;

        if (select == "a")
        {
            cout << "ADD ITEM TO CART" << endl;
            cout << "Enter the item name:" << endl;
            cin.ignore();
            string name;
            getline(cin, name);
            cout << "Enter the item description:" << endl;
            string description;
            getline(cin, description);
            cout << "Enter the item price:" << endl;
            int price;
            cin >> price;
            cout << "Enter the item quantity:" << endl << endl;
            int quantity;
            cin >> quantity;
            ItemToPurchase temp(name, description, price, quantity);
            customer.AddItem(temp);
        }
        else if (select == "d")
        {
            cout << "REMOVE ITEM FROM CART" << endl;
            cout << "Enter name of item to remove:" << endl;
            cin.ignore();
            string name;
            getline(cin, name);
            customer.RemoveItem(name);
        }
        else if (select == "c")
        {
            cout << "CHANGE ITEM QUANTITY" << endl;
            cout << "Enter the item name:" << endl;
      cin.ignore();
            string name;
            getline(cin, name);
            cout << "Enter the new quantity:" << endl;
            int quantity;
            cin >> quantity;
            customer.ModifyItem(quantity, name);

        }
        else if (select == "i")
        {
            cout << "OUTPUT ITEMS' DESCRIPTIONS" << endl;
            cout << customer.GetCustomerName() << "'s Shopping Cart - " << customer.GetDate() << endl << endl;
            customer.PrintDescriptions();
        }
        else if (select == "o")
        {

            cout << "OUTPUT SHOPPING CART" << endl;
            customer.PrintTotal();
        }
        else if (select == "q")
        {
            on = false;
        }

    }

}

最佳答案

这实际上是从底部开始并逐步解决问题的开始。首先，有了 header ，您通常会有 header 保护，有些人使用 #pragma，有些人使用＃ifndef /＃define /＃endif 。我个人更喜欢后者，但是在以为标准的 #pragma的地方工作。因此，您通常遵循工作地点或所获告知的标准。

接下来的帮助是使用:

using namespace std;

当您最终污染 namespace 时，我个人不喜欢它，但是再次，它与标准和遵循编码惯例有关。通常，这只是避免在类名之前键入太多 std::范围的一种方法。

话虽如此，让我们进入代码...在底部，您有ItemToPurchase，除了标准C++之外，其他都不包括其他类，因此最终得到:
// ItemToPurchase.h

#pragma once

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

class ItemToPurchase
{
    private:
        string itemName;
        int itemPrice;
        int itemQuantity;
        string itemDescription;

    public:
        ItemToPurchase()
        {
            itemName = "";
            itemPrice = 0;
            itemQuantity = 0;
            itemDescription = "none";
        }
        ItemToPurchase(string name, string description, int price, int quantity)
        {
            itemName = name;
            itemDescription = description;
            itemPrice = price;
            itemQuantity = quantity;
        }
        void SetName(string name) { itemName = name; }
        void SetPrice(int price) { itemPrice = price; }
        void SetQuantity(int quantity) { itemQuantity = quantity; }
        string GetName() { return itemName; }
        int GetPrice() { return itemPrice; }
        int GetQuantity() { return itemQuantity; }
        void SetDescription(string description) { itemDescription = description; }
        string GetDescription() { return itemDescription; }
        void PrintItemCost() {
            cout << itemName << " " << itemQuantity << " @ $" << itemPrice << " = $" << itemQuantity * itemPrice << endl; }
        void PrintItemDescription() { cout << itemName << ": " << itemDescription << endl; }
};

只是一点说明，您可能应该const限定Get方法。无论如何，以上内容可以放入ItemToPurchase.h头文件中，因为它包含了所需的所有内容。

接下来，您有ShoppingCart类。它专门命名为ItemToPurchase，因此需要包含该 header 。它还应包括其使用的标准类型和类的标题。通常，这是确保 header 不完全依赖于另一个 header 可能包含的 header 的最佳方法。
// ShoppingCart.h

#pragma once

#include "ItemToPurchase.h"
#include <vector>
#include <iostream>
#include <string>

class ShoppingCart
{
    private:
        string customerName;
        string currentDate;
        vector <ItemToPurchase> cartItems;

    public:
        ShoppingCart()
        {
            customerName = "none";
            currentDate = "January 1, 2016";
        }
        ShoppingCart(string name, string date)
        {
            customerName = name;
            currentDate = date;
        }
        string GetCustomerName() { return customerName; }
        string GetDate() { return currentDate; }
        void AddItem(ItemToPurchase newItem) { cartItems.push_back(newItem); }
        void RemoveItem(string name)
        {
            bool temp = true;
            for (int i = 0; i < cartItems.size(); i++)
            {
                if (name == cartItems[i].GetName())
                {
                    cartItems.erase(cartItems.begin() + i);
                    temp = false;
                }
            }
            if (temp == true)
            {
                cout << "Item not found in cart. Nothing removed." << endl << endl;
            }
            else
            {
                cout << endl;
            }
        }
        void ModifyItem(int quantity, string name)
        {
            bool temp = true;
            for (int i = 0; i < cartItems.size(); i++)
            {
                if (name == cartItems[i].GetName())
                {
                    cartItems[i].SetQuantity(quantity);
                    temp = false;
                }
            }
            if (temp == true)
            {
                cout << "Item not found in cart. Nothing modified." << endl << endl;
            }
            else
            {
                cout << endl;
            }
        }
        int GetNumItemsInCart()
        {
            int total = 0;
            for (int i = 0; i < cartItems.size(); i++)
            {
                total += cartItems[i].GetQuantity();
            }
            return total;
        }
        int GetCostOfCart()
        {
            int total = 0;
            for (int i = 0; i < cartItems.size(); i++)
            {
                total += cartItems[i].GetPrice() * cartItems[i].GetQuantity();
            }
            return total;
        }
        void PrintTotal()
        {
            if (cartItems.size() == 0)
            {
                cout << GetCustomerName() << "'s Shopping Cart - " << GetDate() << endl;
                cout << "Number of Items: 0" << endl << endl;
                cout << "SHOPPING CART IS EMPTY" << endl << endl;
                cout << "Total: $0" << endl << endl;
            }
            else
            {
                cout << customerName << "'s Shopping Cart - " << currentDate << endl;
                cout << "Number of Items: " << GetNumItemsInCart() << endl << endl;
                for (int i = 0; i < cartItems.size(); i++)
                {
                    cartItems[i].PrintItemCost();
                }
                cout << endl << "Total: $" << GetCostOfCart() << endl << endl;
            }
        }
        void PrintDescriptions()
        {
            cout << "Item Descriptions" << endl;
            for (int i = 0; i < cartItems.size(); i++)
            {
                cartItems[i].PrintItemDescription();
            }
            cout << endl;
        }
};

现在，我们完成了ShoppingCart.h和ItemToPurchase.h头文件，并且都使用 #pragma一旦对其进行保护。

最后，我们将介绍主要功能，该功能将包含在.cpp文件中。现在，此函数通过名称同时命名ItemToPurchase和ShoppingCart，因此它应同时包含两个头文件。您可以仅包含ShoppingCart.h就可以了，因为它包含ItemToPurcahse.h，但是最好的做法是包括您所命名类型的所有 header 。

最后，这将为您提供一个 main.cpp 文件，该文件应为:
// main.cpp

#include "ItemToPurchase.h"
#include "ShoppingCart.h"
#include <iostream>
#include <string>

int main()
{
    cout << "Enter customer's name:" << endl;
    string name;
    getline(cin, name);

    cout << "Enter today's date:" << endl << endl;
    string date;
    getline(cin, date);

    cout << "Customer name: " << name << endl;
    cout << "Today's date: " << date << endl << endl;

    ShoppingCart customer(name, date);

    bool on = true;
    bool check = true;
    string select;

    while (on)
    {

        cout << "MENU" << endl;
        cout << "a - Add item to cart" << endl;
        cout << "d - Remove item from cart" << endl;
        cout << "c - Change item quantity" << endl;
        cout << "i - Output items' descriptions" << endl;
        cout << "o - Output shopping cart" << endl;
        cout << "q - Quit" << endl << endl;
        cout << "Choose an option:" << endl;
        cin >> select;

        while (check)
        {
            if (select == "a" || select == "d" || select == "c" || select == "i" || select == "o" || select == "q")
            {
                check = false;
            }
            else
            {
                cout << "Choose an option:" << endl;
                cin >> select;
            }
        }
        check = true;

        if (select == "a")
        {
            cout << "ADD ITEM TO CART" << endl;
            cout << "Enter the item name:" << endl;
            cin.ignore();
            string name;
            getline(cin, name);
            cout << "Enter the item description:" << endl;
            string description;
            getline(cin, description);
            cout << "Enter the item price:" << endl;
            int price;
            cin >> price;
            cout << "Enter the item quantity:" << endl << endl;
            int quantity;
            cin >> quantity;
            ItemToPurchase temp(name, description, price, quantity);
            customer.AddItem(temp);
        }
        else if (select == "d")
        {
            cout << "REMOVE ITEM FROM CART" << endl;
            cout << "Enter name of item to remove:" << endl;
            cin.ignore();
            string name;
            getline(cin, name);
            customer.RemoveItem(name);
        }
        else if (select == "c")
        {
            cout << "CHANGE ITEM QUANTITY" << endl;
            cout << "Enter the item name:" << endl;
            cin.ignore();
            string name;
            getline(cin, name);
            cout << "Enter the new quantity:" << endl;
            int quantity;
            cin >> quantity;
            customer.ModifyItem(quantity, name);

        }
        else if (select == "i")
        {
            cout << "OUTPUT ITEMS' DESCRIPTIONS" << endl;
            cout << customer.GetCustomerName() << "'s Shopping Cart - " << customer.GetDate() << endl << endl;
            customer.PrintDescriptions();
        }
        else if (select == "o")
        {

            cout << "OUTPUT SHOPPING CART" << endl;
            customer.PrintTotal();
        }
        else if (select == "q")
        {
            on = false;
        }
    }
}

这一切都应该起作用，并且您的类定义分成各自的.h文件。

关于c++ - 如何将2个类分成单独的.h文件并正确设置它们，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/60233909/

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