操作员的意外输出＆lt;＆lt;在C＆＃x2B;＆＃x2B;上课和用STD ::变种，STD ::访问Union

Question

当前，如果我直接在main（）中使用参数声明类对象，我的代码可以产生正确的输出。但是，当我将班级声明为实例以输出操作员＆lt;＆lt; ，结果不正确。如果有人可以帮助我解决这个问题，我将不胜感激。

这是我的Main（）获得正确的字符串

int main() {
    
    Product dieselMotorBike("A Diesel Motor Cycle", 5488.00, 1);
    Product apples("Granny duBois", 0.78, 2);       
}

输出：

A Diesel Motor Cycle
Granny duBois

这是使用操作员＆lt;＆lt;的完整代码。打印：

#include <iostream>
#include <variant>
#include <string>
#include <cstring>
#include<functional>

using namespace std;

// std::variant<int, float> units, kgs;
using Var = std::variant<int, float>;

typedef union {
   int units;
   float kgs;
} Amount;


class Product {

    public:
        char* selling;
        unsigned length;
        float unitPrice;
        int unitType;
        Amount howMuch;
        Var v;
        // Constructor without arguments 
        Product();
        
        // Constructor with arguments
        Product(const char* s, float unitPrice, int unitType);
        
        ~Product() { delete[] selling; }
        
        /*! 
         *  @brief String length.
         *  @return Value in String @c length.
         */
        unsigned len ( ) const;
    
        /*! 
         *  @brief Append to String.
         *  @param[in] s A String object.
         *  @return A String reference to *this.
         *  @post String will equal the concatenation of itself with @a s.
          */
        Product& operator+= (const Product& s);
    
        char& operator[](size_t idx);
        char operator[](size_t idx) const;
    
        friend std::ostream& operator<<(std::ostream& os, const Product& s) {
           os.write(s.selling, s.length);
            return os;
        }
    
        // Return string length
        int size() { return length; }
};

// Constructor with no arguments
Product::Product() : selling{new char[1] {'\0'}}, unitPrice{0.00}, unitType{0} {}

// Constructor with one argument
Product::Product(const char* s, float unitPrice, int unitType) {
    if (s == nullptr) {
        selling = new char[1]{'\0'};
        length = 0;
        this->unitPrice = 0.00;
        this->unitType = 0;
    } else {
        length = std::strlen(s);
        selling = new char[length + 1];
        std::copy(s, s + length + 1, selling);
        this->unitPrice = unitPrice;
        this->unitType = unitType;
        std::cout << s << "\n";
    }
}

unsigned Product::len ( ) const 
{
    return length;
}

Product& Product::operator+=(const Product& s) {
    unsigned len = length + s.length;
    char* str = new char[len + 1];
    for (unsigned j = 0; j < length; j++) str[j] = selling[j];
    for (unsigned i = 0; i < s.length; i++) str[length + i] = s.selling[i];
    str[len] = '\0';
    delete[] selling;
    length = len;
    selling = str;
    return *this;
}

Product operator+(const Product& lhs, const Product& rhs) {
    Product rv(lhs);
    rv += rhs;
    return rv;
}

char& Product::operator[](size_t idx) { return selling[idx]; }
char Product::operator[](size_t idx) const { return selling[idx]; }

int main() {
    int numItems = 2; int i;
    char temp1[] = "A Diesel Motor Cycle";
    char temp2[] = "Granny duBois";
    Product dieselMotorBike;
    Product apples;
    // dieselMotorBike.selling = temp1;
    strcpy(dieselMotorBike.selling, temp1);
    dieselMotorBike.unitPrice = 5488.00;
    dieselMotorBike.unitType = 1;
    dieselMotorBike.howMuch.units = 4;
    cout << dieselMotorBike << "\n";
    //Product apples("Granny duBois", 0.78, 2);
    Product * myEbayStore[2];
    
    strcpy(apples.selling, temp2);
    apples.unitPrice = 0.78;
    apples.unitType = 2;
    apples.howMuch.kgs = 0.5;
    cout << apples << "\n";
    
    myEbayStore[0] = &dieselMotorBike;
    myEbayStore[1] = &apples;
    for (i = 0; i < numItems; i++) {
        printf("\n%s\n", myEbayStore[i]->selling);
        switch (myEbayStore[i]->unitType) {
            case 1:
                printf("We have %d units for sale\n",
                myEbayStore[i]->howMuch.units);
                break;
            case 2:
                printf("We have %f kgs for sale\n",
                myEbayStore[i]->howMuch.kgs);
                break;
        }
    }
}

输出：

A Diesel Motor Cycle!�
A Diesel Motor Cycle
We have 4 units for sale

Granny duBois
We have 0.500000 kgs for sale

它输出更多“柴油摩托车”的线。我什至不知道如何！”出现在第一行。如何解决？

此外，我阅读了一些用STD ::变体，STD ::访问班级的方法，但不知道该如何编写。请告诉我示例代码以替换它。