我怎样才能在我的数据库程序中添加“减少项目的数量”功能？

Question

我正在为我的期末项目制作一个数据库清单程序。 我真的是 c++ 的新手，到目前为止，这是我的代码：

#include <iostream>
#include <fstream>
#include <string>
#define ss 30
using namespace std;

struct store 
{
    char brand[30];
    char name[30];
    char pc[30];
    int x;
    float price;
}s[ss];
void AddNewItem(int &num)
{
    cout<<"\n \t\t\t   NEW DATA FOR AN ITEM\n\n\n";
    cout<<"Product Code: ";
    cin>>s[num].pc;
    cout<<endl;
    cout<<"Company Name: ";
    cin>>s[num].brand;
    cout<<endl;
    cout<<"Product Name: ";
    cin>>s[num].name;
    cout<<endl;
    cout<<"Product Price ";
    cin>>s[num].price;
    cout<<endl;
    cout<<"Quantity: ";
    cin>>s[num].x;
    num++;
    cout<<endl;
}
void ShowInventoryList(int &num)
{
    if (num==0)
    {
        cout<<"\nThere are no items in the record right now. Please add record.\n\n";
    }
    else{
        cout<<"\n \t\t\t LIST OF ALL ITEMS"<<endl;
        cout<<"Product Code \t Company Name \t Product Name \t Product Price \t Quantity'\t" <<endl;
        for(int i=0;i<num;i++)
        {
            cout<<s[i].pc <<"\t\t"
            <<s[i].brand <<"\t\t"
            <<s[i].name <<"\t\t"
            <<s[i].price <<"\t\t"
            <<s[i].x <<"\t\t"
            <<endl
            <<endl;
        }
    }
}

int main()
{
    ifstream openFile("Inventory.txt");
    string line;
    int menu,number=0;
    do
    {
        cout<<"\n====================   MENU   ====================";
        cout<<"\n                                                ";
        cout<<"\n            1. Add New Item                       ";
        cout<<"\n            2. Show Inventory List                ";
        cout<<"\n            3. Search An item From Record         ";
        cout<<"\n            4. Reduce The Quantity of An Item;    ";
        cout<<"\n            5. Save Item Stock to Text File       ";
        cout<<"\n            6. Show Item Stock from Text File     ";
        cout<<"\n            7. Exit                               ";
        cout<<"\n                                                ";
        cout<<"\n=================================================="<<endl;
        cout<<"\nEnter your choice: ";
        cin>>menu;
        switch(menu)
        {
            case 1:{AddNewItem(number);
                break;}
            case 2:{ShowInventoryList(number);
                break;}

            }
        }
    while(menu!=7);
    cout<<"\nThank you for using our program. Have a good day!";
}

我将项目的数量设置为 int 因为我打算只询问用户他们想要从项目中减少的数量，然后从项目的原始数量中减去它。 我被困在这里，非常感谢您的帮助！ <3

Answer 1

更新：感谢你们的帮助，我设法通过使用这个来做到这一点：

void RemoveItemRecord(int&num)
{
    int c;
    long int pc, qnty;
    cout<<"What do you want to delete from the record?\n Please enter product code of the item:  ";
    cin>>pc;
    cout<<"Enter the amount you want to reduce from the quantity";
    cin>>qnty;
        if(num==0){
        cout<<"\nThere is no data to be deleted.\n\n";}
        else{
            for(c=0;c<num;c++){
                if(s[c].pc=pc){
                    s[c].qnty=s[c].qnty-qnty;
                }
            }
        }
}