QVector

mlong

You may want to open your file before trying to read from it.

pbhuter

Well, obviously - why didn't I see that. However, infile.open() doesn't work. I apparently need some arguments. I looked in the online Qt documentation for QFile, and I don't see anything about "open".

mlong

QFile inherits "open":http://doc.qt.nokia.com/4.7-snapshot/qiodevice.html#open from QIODevice. You want
@
infile.open(QIODevice::ReadOnly);
@

pbhuter

I did

@infile.open(QIODevice::ReadOnly)@

But I'm still having the same issue.

ZapB

Please post a small compilable example that reproduces your problem. Then we can try it out ourselves and will likely be able to help you much easier.

pbhuter

@
QFile infile(_filename);

infile.open(QIODevice::ReadOnly);

QTextStream its(&infile;);

// parse header
bool dataRow = false;

QString line;

while (!dataRow && !its.atEnd())
{
line = its.readLine();

if (line.contains(QRegExp("\\d+\\.?\\d*"))) // check for data row
{
  dataRow = true;
}

} //should have first row of data

_stages = line.toInt();@

I get into the while loop and it seems to think its is empty, so really I'm thinking it's still an issue with QTextStream. Let me know if you need anything else.

ZapB

And what is in your data file please?

pbhuter

test.dat contains:

2
100
50
50
2.5
5
60
10
75
45
30
1.6
2
45
25
25
15

So _stages should pick up the 2 at the top of the file. I then have:

@while (!its.atEnd())
{
int i = 0;
while(i < _stages)
{
line = its.readLine();
_wMasses.push_back(line.toDouble());

line = its.readLine();
_fMasses.push_back(line.toDouble());

line = its.readLine();
_dMasses.push_back(line.toDouble());

line = its.readLine();
_flowRates.push_back(line.toDouble());

line = its.readLine();
_burnTimes.push_back(line.toDouble());

line = its.readLine();
_thrusts.push_back(line.toDouble());

line = its.readLine();
_alphas.push_back(line.toDouble());

i++;
}

line = its.readLine();
_Mass = line.toDouble();

line = its.readLine();
_Alpha = line.toDouble();
}@

Which reads the rest of the file.

ZapB

Does it work if you change this line:

@
infile.open(QIODevice::ReadOnly);
@

to this:

@
infile.open(QIODevice::ReadOnly | QIODevice::Text);
@

pbhuter

No, still doesn't work...

pbhuter

I had:

@if (!(infile.open(QIODevice::ReadOnly)))
{
return 1;
}@

And it goes in and returns 1. Not sure what's going on.

ZapB

Does your process have permissions to read the file? Is some other process locking the file? Is the path correct?

pbhuter

My file was either in the wrong location, or I was trying to run my program from the wrong directory. Thank you so much.

ZapB

Meh, we've all been there, done that at some point. :-) Another trick you can use is to use something like this:

@
QFileInfo fi( fileName );
if ( !fi.isReadable() )
do something
@

Glad you got it working in the end.

pbhuter

Reading input files is always something I struggle with. Now I can get down to the business of writing the code to actually do stuff. Thanks again for everyone's help!

andre

You might want to add some error checking in your parsing code... It is not very save to just assume that your reading and converting worked properly, if you have no control over the input file...

KA51O

another option would be to check if the file you want to open exists before trying to open it.
Just use something like
@if(QFile::exists(filename))
{
QFile file (filename);
if(file.open(QIODevice::ReadOnly)
{
QByteArray strFileContent = file.readAll();
}
}@

This way its easier to find the error when debugging.

PS: Any possible errors are mine and are not to be used by anyone else.