Please help My Delete function doesn't work

[bwilson1]

Hello, I have been working on this code and my only issue is that my Delete function doesn't work.

#include <iostream>
#include <cstdlib>
#include <string>
#include <fstream>
#include <cctype>
#include <conio.h>
using namespace std;

//declare variables
void Add();
void Edit();
void Display();
void Delete();
void Sell();
void Value();

struct Inventory
{
    char title[35], artist[25], type[12];
    int year;
    int price;
    int choice;
    bool dead_flag;




};


int main()
{
    int choice;
    do
    {
        cout << "MENU" << endl;
        cout << "1. Add Record(s): " << endl;
        cout << "2. Display Record: " << endl;
        cout << "3. Edit Records: " << endl;
        cout << "4. Delete Records: " << endl;
        cout << "5. Sell a Title: " << endl;
        cout << "6. Sold Value: " << endl;
        cout << "Please enter your selection.\n> ";
        cin >> choice;

        switch (choice)
        {
        case 1:
            Add();//Add record
            break;
        case 2:
            Display();//Display record
            break;
        case 3:
            Edit();//Edit record
            break;
        case 4:
            Delete();//Delete record
            break;
        case 5:
            Sell();  //Sell record
            break;
        case 6:
            Value(); //value of sold records
            break;


        default:
            cout << "Invalid Selection" << endl;
        }
    }
    while(choice >= 7);

    system("PAUSE");
    return 0;
}



//Add function
void Add()
{
    system("CLS"); //clears screen

    fstream fout;
    Inventory inv;
    char ch;

    fout.open("output.bin", ios::out | ios::binary | ios::app);

    do
    {
        cout << "Enter title: ";
        cin >> inv.title;
        cout << "Enter artist: ";
        cin >> inv.artist;
        cout << "Enter type: ";
        cin >> inv.type;
        cout << "Enter price: ";
        cin >> inv.price;
        cout << "Enter year: ";
        cin >> inv.year;

        //write record to file
        fout.write(reinterpret_cast<char*>(&inv), sizeof(inv));

        cout << "Do you want to add another record? " << endl;
        cin >> ch;
    }
    while(tolower(ch) == 'y');

//close the file
    fout.close();
}



//"Display" function
void Display()
{
    system("CLS"); //clears screen

    Inventory inv;
    fstream fout;

    fout.open("output.bin", ios::in | ios::binary);

    fout.read(reinterpret_cast <char*> (&inv), sizeof(inv));

    while (!fout.eof())
    {

        cout << "\nTitle\t: "   << inv.title;
        cout << "\nArtist\t: "  << inv.artist;
        cout << "\nType\t: "    << inv.type;
        cout << "\nYear\t: "    << inv.year;
        cout << "\nPrice\t: "   << inv.price <<endl <<endl;

        fout.read(reinterpret_cast <char*> (&inv), sizeof(inv));

    }
//close the file
    fout.close();
}



void Edit()
{
    int x;
    Inventory inv;
    fstream fout;

    fout.open("output.bin", ios::in|ios::binary);
    fout.seekg(0, ios::end);
    int count = fout.tellg()/sizeof(inv);
    cout << "\n There are "<< count <<" record in the file";
    cout << "\n Enter Record Number to edit: ";
    cin >> x;

    fout.seekg((x-1)*sizeof(inv));
    fout.read(reinterpret_cast<char*>(&inv), sizeof(inv));

    cout << "Record " << x << " has following data: " << endl;
    Display();
    fout.close();
    fout.open("output.bin", ios::out|ios::in|ios::binary);
    fout.seekp((x-1)*sizeof(inv));
    cout << "\nEnter data to Modify: " << endl;

    fout.write(reinterpret_cast <char*> (&inv), sizeof(inv));
}




void Delete()
{
    Inventory inv;
    char option;
    int position;
    fstream fout;

    fout.open("output.bin", ios::binary | ios::in | ios::out);
    fout.clear();
    fout.seekp( position*sizeof(inv), ios::beg );
    fout.read(reinterpret_cast <char*> (&inv), sizeof(inv));

    cout << endl << endl;
    cout << "Would you like to delete this record? Yes (y) or No (n): ";
    cin >> option;

    option = getch();

    fout.seekp(position*sizeof(inv),ios::beg);
    fout.write(reinterpret_cast <char*> (&inv), sizeof(inv));

    getch();



    fout.close();
}

void Sell()
{


}

void Value()
{


}

[PCrumley48]

In line 186, variable "position" has not been given a value by the function, so the seekp function could return any number of erroneous data.

[Duthomhas]

The best way to handle it is to have a vector of items. Load all the items from file into the vector. Delete the chosen item from the vector. Overwrite the file with the modified vector.

By the way, an "inventory" is a list of items. Your structure above confuses multiple items with a single item.

Make yourself a struct that holds a single item's data, like

struct Record
{
    char title[35];
    char artist[25];
    char type[12];
    int year;
    int price;
    int choice;
    bool dead_flag;
};

Now you can create an "inventory":

typedef std::vector <Record> Inventory;

And use it:

void load_inventory_from_file( const std::string& filename, Inventory& inventory )
{
    ...
}

int main()
{
    Inventory inventory;
    load_inventory_from_file( "foo.bin", inventory );
    ...
}

Hope this helps.