What is the problem on my code

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I'am developing a Book Management System. My Code Writing datas to a txt file. Datas Holding Like;

Book ID Book Name Author Name Page Count-> 213154 Harry Potter and the Philospher's Stone J. K. Rowling 224

I write an update fucntion for when user wants to update some datas, but its not working, its deleting all datas on txt file. How can I fix it ?

What I have tried:

void bkMngment::uptbk()
{

	string bkcategory, idbook, id2, cost, bkname, autname, pgcnt, publ, bked;
	int stock;
	fstream bookreg;
	fstream temp;
	int count = 0;


	cout << "Update Book ";
	temp.open("tempmngsys.txt", ios::app | ios::out);
	temp.open("Bkmngsys.txt", ios::in);

	if (!bookreg)
		cout << "File Not Opening or Not Exist Please Check Again";
	else {

		cout << "Book ID : ";
		cin >> idbook;
		bookreg >> idbook;
		bookreg >> bkcategory;
		bookreg >> autname;
		bookreg >> bkname;
		bookreg >> publ;
		bookreg >> bked;
		bookreg >> pgcnt;
		bookreg >> cost;
		bookreg >> stock;


		while (!bookreg.eof()) {
			if (idbook == id2) {

				cout << "*** UPDATE BOOK ***";
				cout << "Enter New Category";
				cin >> bkcategory;
				cout << "Author Name : ";
				cin >> autname;
				cout << "New Book Name : ";
				cin >> bkname;
				cout << "New Publisher Name : ";
				cin >> publ;
				cout << "Book Edition Number : ";
				cin >> bked;
				cout << "Page Count Of Book: ";
				cin >> pgcnt;
				cout << "Cost Of Book: ";
				cin >> cost;
				cout << "Stock Of Book: ";
				cin >> stock;

				temp << "" << id2;
				temp << " " << bkcategory;
				temp << " " << autname;
				temp << " " << bkname;
				temp << " " << publ;
				temp << " " << bked;
				temp << " " << pgcnt;
				temp << " " << cost;
				temp << " " << stock;
				temp << "\n";
				count++;
			}
			else
				temp << "" << id2;
			temp << " " << bkcategory;
			temp << " " << autname;
			temp << " " << bkname;
			temp << " " << publ;
			temp << " " << bked;
			temp << " " << pgcnt;
			temp << " " << cost;
			temp << " " << stock;
			temp << "\n";

			bookreg >> id2;
			bookreg >> bkcategory;
			bookreg >> autname;
			bookreg >> bkname;
			bookreg >> publ;
			bookreg >> bked;
			bookreg >> pgcnt;
			bookreg >> cost;
			bookreg >> stock;
		}

	}
	cout << endl;
	system("pause");


	bookreg.close();
	temp.close();
	remove("Bkmngsys.txt");
	rename("tempmngsys.txt", "Bkmngsys.txt");
}

Posted 27-Dec-21 22:24pm

CDotpp

Updated 22-Feb-22 9:25am

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OriginalGriff · Answer 1 · 2021-12-27T23:13:00

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

C++

int Double(int value)
   {
   return value * value;
   }

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

Richard MacCutchan · Answer 2 · 2021-12-27T23:49:00

Solution 2

C++

fstream bookreg;
fstream temp;
int count = 0;


cout << "Update Book ";
temp.open("tempmngsys.txt", ios::app | ios::out); // Do you see the
temp.open("Bkmngsys.txt", ios::in);               // problem here?

Posted 27-Dec-21 23:49pm

Richard MacCutchan

v3

I_M_R · Answer 3 · 2022-02-22T09:25:00

Hello,
It seems it is not best way to manage book data by using *.txt file.
I must ask you how did you open your source file ( files ) input file or output file ?
For reading, writing, to append? Files will include data in ansi characters txts or binary file? Binary files are easy to handle if it starts to work, more efficient! It will be good practice to have constant-standrt lentgh of char strings and unique index ( primary key) for each record and holding this last value of that index somehow -somewhere (in a sperate indeks file ). Really hard work to organize these stuff and writing code, debug and commissioning etc.
If someone asks me how will you solve this project i would say that is the database project it will use local database or database server RDMS based database (Ms SQL, my SQL, Interbase, Oracle, ... ) or desktop based database ms Access mdb, foxpro,... . For anyone of them you will need database engine driver for operations through you application software. For Maintenancing operation a GUI will be usefull.
I hope this exp. helps,

Regards,
IM

What is the problem on my code

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