Code not reading file in output

[closed account 4EbCfSEw]

Whenever I try to debug, the command prompt pops up and asked me for my file name. When I type in the name and press Enter, nothing happens. I cannot figure out why. When I try to build in visual studios, I do not get any errors

Here's the command prompt: https://imgur.com/vpw8jD6

Here's the code: https://pastebin.com/5Swqzb5Y (ignore the comments)

please please please help
thank you

[SamuelAdams]

put some cout << "Test # comments in so you can see where in the program it's getting stuck

[closed account 4EbCfSEw]

I've never done that. How and where do I do it?

[Chervil]

A lot of the code is quite fragile. The first problem I found was in entering the file name. If the user simply presses enter when asked for a file name, the cin.get() fails.

From the reference on this site,

c_plus_plus_com wrote:

failbit Either no characters were written or an empty c-string was stored in s.

Hence, in function open_input(), cin.clear() is needed after attempting to read the user input. (the same apples when getting the output file name too).

        cin.get(name, MAX_FILE_NAME + 1); // Gets at most MAX_FILE_NAME characters
        cin.clear();                      // reset cin after failed input
        cin.ignore(81, '\n');             // Remove newline character from keyboard buffer 

That was the easy bit. I gave the program a valid input filname, but since I don't have any sample test data, I just had some random nonsense in the file.

The program entered an infinite loop. This is what I mean by 'fragile', it breaks if there are any problems with either user input or file input.

The fix for the file input was not so very complicated, but it affected more than one line of code.

My current version:

SalesRecord_Array read_records(ifstream& in, int &n)      // Allocate space for records & read them
{
    in >> n;                         // Read number of records
    if (n < 1 || in.fail())
        return NULL;                 // No records to read return

    while (in && in.get() != '\n');  // Clear enter after number of records in file
    
    SalesRecord_Array records;       // Pointer for array of records

    records = new SalesRecord[n];    // allocate space for records 
    if (records == NULL)
    {
        cout << "Can not allocate memory!";
        exit(1);
    }

    int i = 0;
    
    while (i < n && records[i]read(in) ) // Attempt to Read each record
    {
        i++;         
    }
    
    
    if (i != n)
    {
        cout << "Expected number of records: " << n << '\n';
        cout << "Actual number of records:   " << i << '\n';
        n = i;                       // adjust count accordingy
    }
    
    return records;                  // Return pointer to array 
}

The above code doesn't assume the input will work. It tests that each attempt to read a record has succeeded. That means member function read() returns a bool, not void.

In turn it means each part of that function needs its own extra checking, or it could enter an infinite loop, at the place where it tries to read until a newline is found.

bool SalesRecord::read(ifstream& in)       // Read record from input stream, does not read commission values
{
    in.get(item_id, MAX_ID_LEN + 1);       // Read id
    while (in && in.get() != '\n');        // Clear Enter after id
    
    in.get(item_name, MAX_NAME_LEN + 1);   // Read name: Last, First
    while (in && in.get() != '\n');        // Clear Enter after name
    
    in >> quantity_sold >> regular_price;  // Read quantity sold value
    while (in && in.get() != '\n');        // Clear Enter at end of record
    
    return bool(in);
}

[Chervil]

SamuelAdams wrote:

put some cout << "Test # comments in so you can see where in the program it's getting stuck

noobcoder334 wrote:

I've never done that. How and where do I do it?

There's nothing special about it. The program gets stuck. But where?

You might guess, but to find out for sure, add some cout statements interspersed throughout the code. To begin with, I did this in main()

        cout << "\n Before read\n";
        records = read_records(in, num_records);  // Read records & get number of records
        cout << "\n After read\n";

I saw the first line appear, "Before read", but not the second, so that confirmed my suspicions as to where the problem was.

Sometimes you might add many such messages, possibly including the values of some key variables at different points in the program. The main thing, and this is vital, is to make sure that each message is unique. If you put something like "error occurred" is several places, and it is printed out, you won't know which line caused it to be output. So add a simple letter or number to identify the message, such as "error 01", error "02" and so on.

[closed account 4EbCfSEw]

Thank you! I figured it out!