c++ - 我怎样才能让一个类函数接受另一个对象？ (C++)

Question

我希望 Account 类保存一个人的名字、姓氏和他们的余额

Produce 类保存有关一种水果或蔬菜的信息

我希望 Account 类中的 SellProd 函数接受 Produce 对象，以便它可以将该 Produce 的价格添加到此人的余额中。截至目前，该函数给我一个错误提示“Unknown type name 'Produce'

有什么技巧可以让它发挥作用吗？？

#include <iostream>
#include <string>

using namespace std;

class Account
{
    friend class Produce;
private:
    double funds;
    string ownerfirst, ownerlast;
    void addToFunds(double p) { funds += p;};
public:
    Account( string first, string last) { ownerfirst = first; ownerlast = last; funds = 0;};
    void printAccount()
    {
        cout<<"Account Holder: "<<ownerfirst<<" "<<ownerlast<<endl;
        cout<<"Account Balance: "<<funds<<endl;
    };
    void sellProd(Produce a)
    {
        cout<<"Selling: "<<kind<<" | Classified as: "<<type<<endl;
        cout<<"Current Balance: "<<funds<<endl<<"Sell price: "<<price<<endl;
        addToFunds(price);
        cout<<"New Balance: "<<funds<<endl;
    };

};
class Produce
{
private:
    string kind;
    string type; //fruit or vegetable
    double price;
public:
    void printProd()
    {
        cout<<"Type of "<<type<<": "<<kind<<endl;
        cout<<"Selling for: "<<price<<"$"<<endl;
    }; 
    Produce( string k, string t, double p) { kind = k; type = t; price = p;};
};

int main()
{
    Account myAccount("John", "Doe");
    myAccount.printAccount();
    Produce prod1("Tomato", "Fruit", 2.99);
    Produce prod2("Apple", "Fruit", 0.99);
    Produce prod3("Carrots", "Vegetable", 1.49);
    Produce prod4("Potato", "Vegetable", 1.29);

    prod1.printProd();
    myAccount.printAccount();

Answer 1

Produce是在Account之后定义的，所以当编译器看到函数的定义时，还没有看到Produce是什么.只需切换定义，使 Produce 出现在 Account 之前。