QVector



  • I wrote some code at work today, and got a QVector error when I tried to run the code. I was going to ask someone at work. Then I wrote some totally different code at home, and I got a QVector error (not 100% sure it's the same error). Anyone know what's going on? I'm using Qt 4.5 at work and 4.7.3 at home. I can post code, if need be.


  • Moderators

    Without knowing what the errors are, I don't think anyone can be of much help.



  • Here's the qvector.h line it's crashing on:

    Q_ASSERT_X(i >= 0 && i < d->size, "QVector<T>::operator[]", "index out of range");



  • a bit mor code would help, e.g. the code you have written and what you are doing there...
    seams that the index is wrong...



  • from reader.h:
    @
    {
    class Reader
    {
    protected:
    int readFile();

    public:
      Reader(const QString &filename;&#41;
      {
        _filename = filename;
        if (readFile(&#41;&#41;
        {
          _filename = "";
        }
      };
      virtual ~Reader(&#41;
      {
      };
    
      virtual bool isValid();
    
      int getStages()
      {
        readFile&#40;&#41;;
        return _stages;
      };
    
      QVector<double> getWetMasses(&#41;
      {
        readFile(&#41;;
        return _wMasses;
      };
    

    QVector<double> getFuelMasses()
    {
    readFile();
    return _fMasses;
    };

    QVector<double> getDryMasses()
    {
    readFile();
    return _dMasses;
    };

    QVector<double> getFlowRates()
    {
    readFile();
    return _flowRates;
    };

    QVector<double> getBurnTimes()
    {
    readFile();
    return _burnTimes;
    };

    QVector<double> getThrusts()
    {
    readFile();
    return _thrusts;
    };

    QVector<double> getAlphas()
    {
    readFile();
    return _alphas;
    };

    double getRVMass()
    {
    readFile();
    return _RVMass;
    };

    double getRVAlpha()
    {
    readFile();
    return _RVAlpha;
    };

      QString filename(&#41;
      {
        return _filename;
      };
    
    private:
      QString _filename;
      int _stages;
      QVector<double> _wMasses;
    

    QVector<double> _fMasses;
    QVector<double> _dMasses;
    QVector<double> _flowRates;
    QVector<double> _burnTimes;
    QVector<double> _thrusts;
    QVector<double> _alphas;
    double _RVMass;
    double _RVAlpha;
    };
    }@

    from reader.cpp:

    @{
    int ret = 0;

    if (_filename.isEmpty())
    {
    return 1;
    }

    // create QFile, and open and initialize QTextStream
    QFile infile(_filename);
    if (!(infile.open(QIODevice::ReadOnly)))
    {
    return 1;
    }

    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();

    //read rest of file
    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();
    _RVMass = line.toDouble();

    line = its.readLine();
    _RVAlpha = line.toDouble();
    }

    return ret;
    }@

    That's the code that I'm pretty sure it crashes on. In main.cpp I initialize the variables (as ints, or doubles, or QVector<double>s, but I'm adding stuff to the variables in the reader.cpp. The work code is the same, just with different variables.

    Thanks for any help.

    Edit : @ added by Eddy. Please use the code button on top of this edit field to make code more readable for others



  • Run your app in the debugger, then when it breaks due to hitting this assertion click up in the call stack to your code to see which line is causing the problem and to investigate what value the index has and why.



  • A huge code paste and not a single usage of operator[]... please, debug your code and paste some RELEVANT sections.



  • Well, now it doesn't crash. I didn't change any code from when I posted the initial post last night, so there's no reason for it to be working, now. But it does. Sort of. I'm now having a problem with QFile:

    QFile infile(_filename) where _filename = test.dat (an ASCII text file).

    infile shows up as {...} when I step through the code, so my input file never actually gets read. Anyone have an idea as to why? Or should I just wait 12 hours for VS2010/Qt to magically work for me...



  • You say you use VS2010, then have you built Qt framework with VS 2010?
    //the Qt binaries built with VS2008 might give you weird run-time errors if the application is built with VS2010



  • There is no magic. You must have changed the build somehow (stale file perhaps). We cannot tell from your description what the problem is. Please provide a clear description of the problem and ideally a small compilable example that reproduces it.



  • Please disregard the additional problem from my last post. I'm actually having a problem with

    QTextStream its(&infile;);

    infile is loading the name of the input file, but QTextStream its isn't actually reading the file. I go on to do:

    line = its.readLine(), but line always shows up as "" (even though the first line of the file is a 2).

    Anyone able to help, I would appreciate it. Thanks in advance.



  • CODE:

    QFile infile(_filename);
    /* if (!(infile.open(QIODevice::ReadOnly)))
    {
    return 1;
    }*/

    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();


  • Moderators

    Please use the code tag (button on the right with <> symbol on it)
    "Forum help":http://developer.qt.nokia.com/wiki/ForumHelp



  • @ QFile infile(_filename);
    /* if (!(infile.open(QIODevice::ReadOnly)))
    {
    return 1;
    }*/

    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();@

    Sorry, I didn't notice it didn't post correctly.


  • Moderators

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



  • 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".


  • Moderators

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



  • I did

    @infile.open(QIODevice::ReadOnly)@

    But I'm still having the same issue.



  • 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.



  • @
    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.



  • And what is in your data file please?



  • 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.



  • Does it work if you change this line:

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

    to this:

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



  • No, still doesn't work...



  • I had:

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

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



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



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



  • 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.



  • 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!



  • 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...



  • 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.


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