Question

I have designed a linklist based BookStore in which book’s attributes will be stored in a node & so on. Plus at the end of program, I have to save all database into text file (I tried binary reading but damn I got me killed & couldn’t do it) & then reload all info, of each book one by one & store it in nodes & re-make the LinkList.
Now saving is done & no issue at all. But Im having issues in reading from text file.

Saving structure in file is:::

BookID(int) – BookName(string) – Author(string) – BookType(string) – Copies(long) – Price(long) – ‘\n’ (to go to next line)

EXAMPLE:
1 ObjectOrientedParadigm R.Lafore Coding 5 900
2 ObjectOrientedParadigm R.Lafore Coding 5 900
and so on……

Here is the saving function.

bool BookStoreDataBase<mytype>::save_all_data()
{
    if(!is_Empty()) //if list is not empty
    {
        BOOK<mytype> *temp = head;   //created a copy of head
        ofstream file("database.txt", ios_base::app); //created file, to write at the end (append)
        while(temp != tail) //while list ends
        {
            file<<temp->ID<<' '<<temp->bookName<<' '<<temp->author<<' '<<temp->book_type<<' '<<temp->copies<<' '<<temp->price<<' ';  //write all info
            temp = temp->next; //move temp to next node
        }
        file<<temp->ID<<' '<<temp->bookName<<' '<<temp->author<<' '<<temp->book_type<<' '<<temp->copies<<' '<<temp->price<<' '; //for last book's info
        return true; //to confirm sucessfull writing
    }
    else //if list is empty
    {
        return false; //to confirm error in writing
    }
}

PROBLEM:: When I start reading, first line is read fine & stored in list, but for the next time, I can’t make file to read from the next line, hence ‘\n’. & that creates the problem. File again reads the first line & 2nd node is created with same data.

Loading Function:

void BookStoreDataBase<mytype>::load_all_data()
{
    int ID;         //variable to store ID of a book
    string bookName;//string to store name of a book
    string author;  //string to store name of author of book
    string book_type;//string to store type of a book
    long copies;    //variable to store no. of copies a book
    long price;     //variable to store price of a book
    string status;  //to store status of a book, either its in stock or not


    ifstream file("database.txt");
    while(file) //I have tried file.eof but its not working, don't know why
    {
        file>>ID>>bookName>>author>>book_type>>copies>>price>>status; //read file

        BOOK<mytype> *temp = new BOOK<mytype>(0, 0, bookName, author, book_type, copies, price);  //create a new node in memory and save all the data

        if(is_Empty()) //if list is empty, then make 1st node
        {
            head = tail = temp;
        }
        else //other wise make the next node
        {
            tail->next = temp;
            temp->prev = tail;
            tail = temp;
        }
    }
}

MOREOVER
Reading is done 1 time less than the real record. i.e. If .txt has record of 4 books, then 3 nodes are created, (& info of only 1st is repeated in every node), whereas it should read & create 4 nodes!

I’m a beginner, any good help will be much appreciated.

Answer 1

I would suggest you get the whole line using std::getline(), and then use stringstream class to read in everything from that into the respective variables.