Reading .txt file info into variables

sheehan1234

How do I read in a text file and assign the integers in that file to my own variables?

giesbert

That depends, as always :-)
I have no oidea, how the structure of the file is.
Let's gess, one line contains one integer.
Then you could just read the whole file into a QStringList, iterate of the entries and call toINt on each of them.

sheehan1234

Thank you very much Gerolf. I found this code snippet which supposedly puts my text file into a QStringList

@QStringList stringList;
QFile textFile("test.txt");
QTextStream textStream(&textFile);
while (true)
{
QString line = textStream.readLine();
if (line.isNull())
break;
else
stringList.append(line);
}@

If that is done correctly, how do I go about iterating through it?

sheehan1234

I have QStringList of integers that I read in from a file. How do I iterate through this list to: a) save each value b) cast each to an integer.

mlong

I'm not sure what you mean by "save each value" but iterating through a QStringList is fairly simple. There are a number of ways to do so.

@
QStringList list;

// iterate through each element of list (which will be accessible via the QString "str")
foreach (QString str, list)
{
...
int value = str.toInt(); // get integer representation of str
...
}
@

BTW, This stuff is very well-documented.

sheehan1234

I meant to say store each into a variable, which you answered. However I'm trying to do so in the following code, and when I try to print the value, nothing is displayed. Am I reading my text file into the QStringList incorrectly?

@int main()
{
QStringList stringList;
QFile textFile("test.txt");
QTextStream textStream(&textFile);
while (true)
{
QString line = textStream.readLine();
if (line.isNull())
break;
else
stringList.append(line);
}

foreach(QString str, stringList)
{
    int value = str.toInt();
    cout << value;
}
return 0;

}
@

mlong

You need to call "textFile.open()":http://doc.qt.nokia.com/4.7-snapshot/qfile.html#open

Be sure and check its return value. There's an example in the QFile docs.

mlong

A cleaner implementation would probably be:

@
QStringList stringList;
QFile textFile("test.txt");
if (textFile.open(QIODevice::ReadOnly)
{
QTextStream textStream(&textFile);
while (!textStream.atEnd())
{
stringList.append(textStream.readLine());
}
}
@

Caveat: Brain to keyboard. Untested code. Not responsible for silly errors. YMMV

sheehan1234

that worked! thank you very much!

goetz

[quote author="sheehan1234" date="1317152090"]
If that is done correctly, how do I go about iterating through it?[/quote]

@
foreach(const QString line, stringList) {
// do something with the line
}
@

andre

This discussion looks a lot like "this":http://developer.qt.nokia.com/forums/viewthread/10146/ one...

goetz

[quote author="Andre" date="1317189187"]This discussion looks a lot like "this":http://developer.qt.nokia.com/forums/viewthread/10146/ one...[/quote]

I merged both threads.

sheehan1234

I have the code exactly as you all have showed me but there was no output. so i put some print statements inside of the loops to see if the compiler was even entering the loops and it is not. What am I doing wrong?

@int main()
{
QStringList stringList;
QFile textFile("test.txt");
if (textFile.open(QIODevice::ReadOnly))
{
QTextStream textStream(&textFile);
while (!textStream.atEnd())
{
stringList.append(textStream.readLine());
cout << "test1";
}
}
foreach(const QString line, stringList)
{
cout << "test2";
cout << line.toStdString();
}
return 0;
}@

vsorokin

Are you sure that your test.txt are in same directory that your executable file?

mlong

You should print an error message if it cannot open the file.
@
if (...open...)
{
...
}
else
{
// tell me about it
}
@