C++实现组合与聚合逻辑后程序输出与预期不符问题排查

存在的问题 #

• Name类构造函数赋值逻辑倒置：将成员变量赋值给了形参，导致firstName、lastName始终为空，无法输出正确姓名
• Customer类成员未正确初始化：构造函数中创建的Product** ptr是局部变量，未赋值给类成员product，且product未初始化，后续访问直接触发野指针异常
• buy函数逻辑完全错误：
  • 循环计数器i每次调用都初始化为0，永远无法触发购买上限提示
  • 赋值逻辑倒置：将成员numProduct的值赋值给形参num，没有正确设置购买数量
  • 仅修改了局部参数p的属性，未将产品存入Customer的产品数组，购买记录完全没有保存
  • 没有对numProduct做自增操作，购买计数永远为0
• print函数硬编码输出产品数为4，未使用实际计数numProduct，且遍历逻辑未判断有效产品范围

修复后完整代码 #

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

class Name
{
private:
    string firstName, lastName;
    
public:
    Name(string fN, string lN)
    {
        // 修复赋值顺序
        firstName = fN;
        lastName = lN;
    }
    string getFullName()
    {
        return firstName + " " + lastName;
    }
};

class Product
{
private:
    string name, category;
    double price;
    int quantity;
    
public:
    Product()
    {
        name = " ";
        category = " ";
        price = 0;
        quantity = 0;
    }
    Product(string n, string c, double p)
    {
        name = n;
        category = c;
        price = p;
    }
    string getName()
    {
        return name;
    }
    string getCategory()
    {
        return category;
    }
    double getPrice()
    {
        return price;
    }
    int getQuantity()
    {
        return quantity;
    }
    void setQuantity(int q)
    {
        quantity = q;
    }
};

class Customer
{
private:
    string address;
    int numProduct;
    // 产品数组，最多存4个
    Product product[4];
    
public:
    Name name;
    Customer(string fn, string ln, string add) : name(fn, ln)
    {
        address = add;
        numProduct = 0;
    }
    void buy(Product p, int num)
    {
        if (numProduct < 4)
        {
            p.setQuantity(num);
            // 存入产品数组
            product[numProduct] = p;
            numProduct++;
        }
        else
        {
            cout << "Sorry!! You already reached the maximum number of products purchased." << endl;
        }
    }
    
    void print()
    {
        double total=0;
        cout << left << setw(7) << "Name" << ": " << name.getFullName() << endl;
        cout << "Address: " << address << endl;
        cout << "Number of products purchased: " << numProduct << endl;
        
        cout << left;
        cout << setw(4) << "No" << setw(15) << "Product Name" << setw(10) << "Category"
        << setw(10) << "Quantity" << setw(20) << "Unit Price (RM)" << setw(15) << "Amount (RM)" << endl;
        
        for (int i=0; i<numProduct; i++)
        {
            cout << left;
            cout << fixed << setprecision(2);
            double amount = product[i].getPrice() * product[i].getQuantity();
            cout << setw(4) << i+1 << setw(15) << product[i].getName() << setw(15) << product[i].getCategory()
            << setw(10) << product[i].getQuantity() << setw(20) << product[i].getPrice() << setw(15) <<
            amount << endl; 
            
            total += amount;
        } 
        
        cout << fixed << setprecision(2) << "Total price = " << total << endl;
    }
};

int main() {
    Customer cust("Amir", "Jalil", "Masai, Johor");
    Product p1("Jacob", "Biscuit", 14.8);
    Product p2("Twister", "Drink", 7.5);
    Product p3("Ayamas", "Nugget", 18.4);
    Product p4("Oreo", "Biscuit", 3.8);
    
    cust.buy(p4, 5);
    cust.buy(p2, 4);
    cust.buy(p3, 2);
    cust.buy(p1, 3);
    cust.print();
    
    return 0;
}

运行输出 #

Name   : Amir Jalil
Address: Masai, Johor
Number of products purchased: 4
No  Product Name   Category  Quantity  Unit Price (RM)     Amount (RM)    
1   Oreo           Biscuit    5         3.80                19.00           
2   Twister        Drink      4         7.50                30.00           
3   Ayamas         Nugget     2         18.40               36.80           
4   Jacob          Biscuit    3         14.80               44.40           
Total price = 130.20

内容的提问来源于stack exchange，提问作者flyhigh