Inventory Program without class

[brianit41]

I'm trying to write a program that uses a structure to store the inventory data and then manipulate them using a menu with the following tasks:
1. add new records to the file
2. display any record in the file
3. change any record in the file

Everything compiled. Issues is when viewing i am missing data that was entered.
I tried looking at all the code and seem i dont know much about advanced file operation and didn't understand the documentation as well. http://www.cplusplus.com/doc/tutorial/files/

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

const int size=51;
const int numRec=5;

struct Inventory
{
	char    detail[size];		//item description
	int 	quantity;
	double 	wCost,
			rCost;
	int 	month,
			day,
			year;
};

void add(Inventory);								 
void display(Inventory);								
void change(Inventory);



int main()
{
    int choice, record=1;
    char again;
    
	Inventory item = {"", 0, 0.0};   //Creating empty structures for members
	
	fstream inventory("items.dat", ios::out|ios::binary);

	//Writing blanks
	for (int count =1;count < numRec;count++)
	{
        //cout<<"Writing Blanks Records: "<<count<<endl;
        inventory.write(reinterpret_cast<char *>(&item), sizeof(item));
    }
	
	do
	{
	 cout << fixed << showpoint << setprecision(2);  
     cout<<"\nInventory Managment"<<endl;  

     cout << "Please make a selection, 1 through 4." << endl; 
     cout << "1. Add a new record" << endl;  
     cout << "2. View an exisitng record" << endl;  
     cout << "3. Change an exisitng record" << endl;  
     cout << "4. Exit" << endl;  
     cout << endl;  
     cout <<"Enter your choice (1-4): ";  
     cin >> choice; 
      
         while(choice < 1 || choice > 4)  
    
             {  
                 cout << "Invaild selection!" << endl;  
                 cout << "Please enter your choice (1-4) : "<< endl;  
                 cin >> choice;
                 
        	 }  
	
	  
       switch(choice)  
        {  

		case 1:	    cout<< "Record" <<record++<<endl;
                    add(item);  
                    break;  
        case 2:	    display(item);  
                    break;  
        case 3:	    change(item);  
                    break;  
        default:    cout << "Invalid selection" << endl;  
              
        }  
        
        cout<<"\nWould you like to go back to menu?(Y/N): ";
        cin>>again;
     }while(again=='Y'||again=='y');
                  
  
  
    inventory.close();

    system("pause");  
    return 0;  

}

 void add(Inventory item)											

 {  
     
     //Inventory item;  
     fstream inventory("item.dat",ios::out|ios::binary);

     inventory.seekp(sizeof(item), ios::end);

     cout<< "\n\nItem description: ";
     cin.ignore();
     cin.getline(item.detail, size);
	
    	cout<<"How many? Quantity: ";
    	cin>>item.quantity;
    	
    	while (item.quantity<0)
    	{
    		cout<<"Error. Re-Type.\n";
    		cout<<"Cannot be less than 0.\n";
    		cout<<"How many? Quantity: ";
    		cin>>item.quantity;
    	}
    	
    	cout<<"Wholesale cost: $";
    	cin>>item.wCost;
    	
    	while (item.wCost<0)
    	{
    		cout<<"Cannot be less than 0.\n";
    		cout<<"Wholesale cost: $";
    		cin>>item.wCost;
    	}
    	
    	cout<<"Retail cost: $";
    	cin>>item.rCost;
    	
    	while (item.rCost<0)
    	{
    		cout<<"Cannot be less than 0.\n";
    		cout<<"Retail cost: $";
    		cin>>item.rCost;
    	}
    	
    	cout<<"What is the date added to invetory: \n";
    	cout<<"Month: ";
    	cin>> item.month;
    	
    	while (item.month<=0||item.month>12)
    	{
    		cout<<"Error. Re-Type.\n";
    		cout<<"Must be between 1-12.\n";
    		cout<<"Month: ";
    		cin>> item.month;
    	}
    	
    	cout<<"Day: ";
    	cin>>item.day;
    	while (item.day<=0||item.day>31)
    	{
    		cout<<"Error. Re-Type.\n";
    		cout<<"Must be between 1-31, depending on the month.\n";
    		cout<<"Day: ";
    		cin>>item.day;
    	}
    	
    	cout<<"Year: ";
    	cin>>item.year;
    	while (item.year<1900||item.year>2999) 
    	{
    		cout<<"Error. Re-Type.\n";
    		cout<<"Must be between 19xx-2xxx.\n";
    		cout<<"Year: ";
    		cin>>item.year;
    	}
    
    	inventory.write(reinterpret_cast<char *>(&item), sizeof(item));
    	
    	//close the file
    	inventory.close();
    	
 } 
 
 void display (Inventory item) 

 {  
     
     //binary input
     fstream inventory("item.dat", ios::in|ios::binary);
     
     //inventory.seekg (sizeof(item), ios::beg);
     inventory.read(reinterpret_cast<char *>(&item), sizeof(item));
     
     while (!inventory.eof())
     {
     cout << "Description: " << item.detail << endl;  
     cout << "Quantity: " << item.quantity << endl;  
     cout << "Wholesale cost: " << item.wCost << endl;  
     cout << "Retail price: " << item.rCost << endl;  
     cout << "Date Added: "<<item.month<<"/"<<item.day<<"/"<<item.year<<endl; 
     inventory.read(reinterpret_cast<char *>(&item), sizeof(item));
     }
     //close the file
     inventory.close();
     
 }  
 
 void change (Inventory item)		//changing record						

 {  
     int recNum;
      
     //binary input
     fstream inventory("item.dat", ios::in|ios::out|ios::binary);
     
     // Get the record number of the desired record.
	 cout << "Which record do you want to edit? ";
	 cin >> recNum;

	 // Move to the record and read it.
	 inventory.seekg(recNum * sizeof(item), ios::beg);
     inventory.read(reinterpret_cast<char *>(&item), sizeof(item));
     
     // Display 
     cout << "Description: " << item.detail << endl;  
     cout << "Quantity: " << item.quantity << endl;  
     cout << "Wholesale cost: " << item.wCost << endl;  
     cout << "Retail price: " << item.rCost << endl;  
     cout << "Date Added: "<<item.month<<"/"<<item.day<<"/"<<item.year<<endl; 
     
     // Add New Record
      cout<< "\n\nItem description: ";
     cin.ignore();
     cin.getline(item.detail, size);
	
    	cout<<"How many? Quantity: ";
    	cin>>item.quantity;
    	
    	while (item.quantity<0)
    	{
    		cout<<"Error. Re-Type.\n";
    		cout<<"Cannot be less than 0.\n";
    		cout<<"How many? Quantity: ";
    		cin>>item.quantity;
    	}
    	
    	cout<<"Wholesale cost: $";
    	cin>>item.wCost;
    	
    	while (item.wCost<0)                                                   //Input for Sales
    	{
    		cout<<"Cannot be less than 0.\n";
    		cout<<"Wholesale cost: $";
    		cin>>item.wCost;
    	}
    	
    	cout<<"Retail cost: $";
    	cin>>item.rCost;
    	
    	while (item.rCost<0)
    	{
    		cout<<"Cannot be less than 0.\n";
    		cout<<"Retail cost: $";
    		cin>>item.rCost;
    	}
    	
    	cout<<"What is the date added to invetory: \n";                       //Input for date
    	cout<<"Month: ";
    	cin>> item.month;
    	
    	while (item.month<=0||item.month>12)
    	{
    		cout<<"Error. Re-Type.\n";
    		cout<<"Must be between 1-12.\n";
    		cout<<"Month: ";
    		cin>> item.month;
    	}
    	
    	cout<<"Day: ";
    	cin>>item.day;
    	while (item.day<=0||item.day>31)
    	{
    		cout<<"Error. Re-Type.\n";
    		cout<<"Must be between 1-31, depending on the month.\n";
    		cout<<"Day: ";
    		cin>>item.day;
    	}
    	
    	cout<<"Year: ";
    	cin>>item.year;
    	while (item.year<1900||item.year>2999) 
    	{
    		cout<<"Error. Re-Type.\n";
    		cout<<"Must be between 19xx-2xxx.\n";
    		cout<<"Year: ";
    		cin>>item.year;
    	}
     
     
     // Move back to the beginning of the this record's position.
	 inventory.seekp(recNum * sizeof(item), ios::beg);

	 // Write the new record over the current record.
	 inventory.write(reinterpret_cast<char *>(&item),
		            sizeof(item));
     
     //close the file
     inventory.close();
     
 }

[Peter87]

Note that this will loop numRec-1 times.
for (int count =1;count < numRec;count++)

Not sure but maybe you should not open the same file with multiple fstreams at the same time.

[brianit41]

So i shouldn't do the fstream in functions but instead put everything in main?

[Peter87]

I was more thinking that you keep inventory in main open AND call functions that opens the same file. Maybe you should close it before you enter the do-while loop.

[brianit41]

Yeah i don't know how to make the call function open the same file.
It seem to me the item.dat is not syncing with the data i entered after closing the program. So whenever i try to view the data it goes blank.
If i try to create the blanks records with the for loop will it overwrite it when i activate the program again? Do i even need the blank records?
My main issue is adding the data with the functions without overwriting the previous entry and the data actually saving to the file.