创建友元函数以访问两个类的私有变量

Question

问题是通过添加一个是两个类的朋友的函数来访问两个不同类的输出的私有变量。

class Salesperson;

class Sale {
private:
    string date;
    double total;
    int SalespersonIdNum;
public:
    Sale(string, double, int);
    friend void display(Sale &, Salesperson &);
};
Sale::Sale(string d, double t, int S) {
    >>d = date;
    >>t = total;
    >>S = SalespersonIdNum;
}
//Salesperson class
class Salesperson {
private:
    int idNum;
    string lastName;
public:
    Salesperson(int, string);
    friend void display(Sale &, Salesperson &);
};
Salesperson::Salesperson(int i, string l) {
    >>i = idNum;
    >>l = lastName;
}

void display(Sale &s, Salesperson &sp) {
    //Output Sale info
    cout << " ID of person who completed sale: " << s.SalespersonIdNum << endl;
    cout << " Sale Total: " << s.total << endl;
    cout << " Sale Date: " << s.date << endl;
    //Output Saleperson info
    cout << " Sales Person ID: " << sp.idNum << endl;
    cout << " Sales Person Last Name: " << sp.lastName << endl << endl;
}

int main() {

    Sale s1("10/06/2008", 78.45, 123);
    Salesperson emp1(123, "Pelletier");

    display(s1, emp1);

    Sale s2("05/21/2010", 162.59, 321);
    Salesperson emp2(321, "Howel");

    display(s2, emp2);

    return 0;
}

理想情况下，显示函数应该能够访问由我的对象定义定义的变量，但是当我去运行并显示它们时，函数会显示这个。

ID of person who completed sale: 124                                                    
 Sale Total: 2.07482e-317                                                                
 Sale Date:                                                                              
 Sales Person ID: 6299816                                                                
 Sales Person Last Name:  

 ID of person who completed sale: 1677231376                                             
 Sale Total: 2.07417e-317                                                                
 Sale Date:                                                                              
 Sales Person ID: 1                                                                      
 Sales Person Last Name:                                                                 


...Program finished with exit code 0                                                     
Press ENTER to exit console.

根据我的理解，朋友函数应该这样工作，但问题可能出在构造函数中，但我认为这些也正确完成。至于输出可能是我在输出内存地址什么的，但我对此一无所知

Answer 1

您的分配在构造函数中的方向错误。

Sale::Sale(string d, double t, int S) {
    d = date;
    t = total;
    S = SalespersonIdNum;
}

他们必须是：

Sale::Sale(string d, double t, int S) {
    date = d;
    total = t;
    SalespersonIdNum = S;
}

使用列表初始化语法会更好。

Sale::Sale(string d, double t, int S) :
    date(d),
    total(t),
    SalespersonIdNum(S) { }