How to add data in array QT C++

Question

I want to read line by line a text file and add each line in a array, I try something like that, but something is wrong with my array, what ?

QFile inputFile("C:\\pepoles.txt");
if (inputFile.open(QIODevice::ReadOnly))
{
    QTextStream in(&inputFile);
    QString pepoles[1000];
    while ( !in.atEnd() )
    {
        QString line = in.readLine();
        pepoles[] = line;
    }
    ui->lineEdit->setText(pepoles[0]);
}
else{
    QMessageBox::critical(this, "Ouups",
                          "Le fichier est introuvable ou vide...");
}

inputFile.close();
}

Thanks !

Solution 1

Keep track of the number of lines you've read, and index pepoles with it. Also, make sure you don't exceed your arrays capacity.

   int lineNum = 0;
   QFile inputFile("C:\\pepoles.txt");
   if (inputFile.open(QIODevice::ReadOnly))
   {
      QTextStream in(&inputFile);
      QString pepoles[1000];
      while ( !in.atEnd() && lineNum < 1000)
      {
         QString line = in.readLine();
         pepoles[lineNum++] = line;
       }

Solution 2

You should use QStringList instead of QString [1000];.

Then you can add line simply with

peoples << line;

---

Now your syntax is incorrect. You are trying to assign line to an array, or what? You can only assign line to the specified element of array, like

peoples[i] = line;

But you'd better use first approach.

Solution 3

Also this will show the first line only :

ui->lineEdit->setText(pepoles[0]);

You probably want something like this (if pepoles is a QStringList)

ui->lineEdit->setText(pepoles.join());

The join() method will make a QString that concatenates all items in the qstringlist

Edit: And maybe use something else than a LineEdit ;)

Solution 4

You need to specify at which position you want to copy the string. For example:

pepoles[0] = line;

will copy the string to the first element of the array. Obviously you will need a variable to iterate over the array, so that in each loop you'll copy the new string to the next position in the array.

You should probably use a QStringList instead of an array to make things easier and safer, so that you won't write past the end of the array by accident. For example, you can define a pepoles like this;

QStringList pepoles;

Then, every time you want to append a new string to the end, you do:

pepoles << line;

Here's the documentation of QStringList on how to use it: http://doc.qt.digia.com/qt/qstringlist.html#details

You can also use an std::vector<QString> instead:

std::vector<QString> pepoles;

In that case, you insert strings at the end with:

pepoles.push_back(line);

Read up on std::vector here: http://www.cplusplus.com/reference/stl/vector

std::vector is not part of Qt. It's provided by the standard C++ library.

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Comments

[Random78952]

Can i declare pepoles array without size ?

[Jason]

No. If you want to not limit the size use QStringList as in Nikos' suggestion.

[Anthony]

This also seems like a good fit for QVarLengthArray.