Both If and Else condition execute C++

Question

I have a function for deleting data from a text file.

I'm having problems when valid input is entered:

if I enter bad input, it only executes the else part, as expected
if I enter valid input, it executes both the if and the else part.

Here is my code:

void Member::processTransaction()
{
    fstream f;

    f.open("Member.txt",ios::in|ios::out);

    int x = 0, y = 0, z = 0;

    while (!f.eof())
    {
        f >> idList[x] >> nameList[y];

        if (id == idList[x])
        {
            cout << idList[x] << "\t" << nameList[x] << endl;

            cout << "Do you want to delete the entry (Y/N) : " << endl;

            char deleteEntry = getche();

            if(deleteEntry=='Y'||deleteEntry=='y')
                deleteInformation();  

            f.close();
        }
        else
        {
            cout << "No Matches Found!";
        }
    }
}

in the output. If I enter True, it executes and displays "No Matches Found". If I enter false, it only displays "No Matches Found" and its fine.

*replace* the `f.close()` with a `break` or `return`. the `fstream` destructor closes the file. — Cheers and hth. - Alf, May 28 '14 at 22:52
The `no matches found` should be out of the loop if actually no matches are found. The way you do this will not handle the file hosting multiple sets of your input variables. — CodeAngry, May 28 '14 at 22:57
if you click @Chad 's link you'll see the issue has to do with when EOF occurs. EOF is not set until you try to read *past* the end of the file — Ryan Haining, May 29 '14 at 04:29

score 10 · Answer 1 · answered May 28 '14 at 22:53

while(!f.eof()){ is almost always a mistake. This case is no exception.

eof means you tried to read something previously, and it failed due to end of file. It's false if you have read the whole file exactly, and it's false if you close the file before trying to read past the end as you do in this example. And it's false if the stream is in an error state for another reason.

Instead , change to while (f >> idList[x] >> nameList[y]), and use break; if you want to exit the loop for some other reason than this read failing.

CodeAngry · Answer 2 · 2014-05-28T23:18:22.733

0

void Member::processTransaction() {
    fstream f;
    f.open("Member.txt", ios::in | ios::out);
    int x = 0, y = 0, z = 0;
    bool found = false; // found or not?
    // search the file now.
    while(!f.eof() && !found) {
        f >> idList[x] >> nameList[y];
        if(id != idList[x]) {
            continue;
        }
        cout << idList[x] << "\t" << nameList[x] << endl;
        cout << "Do you want to delete the entry (Y/N) : " << endl;
        char deleteEntry = getche();
        if(deleteEntry == 'Y' || deleteEntry == 'y') {
            deleteInformation();
        }
        found = true;
    }
    f.close(); // close here
    // not found only after you're done searching.
    if(!found) {
        cout << "No Matches Found!";
    }
}

Your code is bad. My code is just less bad. Your entire way of doing this is flawed. But this is the right wrong way to do it.

edited May 28 '14 at 23:18

answered May 28 '14 at 23:00

CodeAngry

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Most of the obvious errors in his code I also see in yours, how is yours less bad? – Mooing Duck May 28 '14 at 23:18
@MooingDuck This code is like a joke. You don't explain it. But you'll figure it out. – CodeAngry May 28 '14 at 23:20
@CodeAngry it's not a good joke though. – Massa May 28 '14 at 23:21
@Massa This code will not print both things out. If found, `No matches` is not printed as it's not tested inside the loop. That's the only thing. Plus the file is closed outside the loop. – CodeAngry May 28 '14 at 23:23

Both If and Else condition execute C++

2 Answers2