QTableWidget item->settext() Segfaulting QT 5.8

dcbdbisVA

Good evening. I am having a segfault and I cannot find out why. According to the web searches that I have done things are OK in the code.

I am reading in a file, adding a row to the tableWidget, then attempting to parse and put data in the same. It segfaults on the first "setText" line.

"Cell[]" is a QString array. "row" is an int. "line" is a QString.


fp = fopen("Procedures.txt","r");
   if(fp != NULL)
   {
   QTextStream file(fp,QIODevice::ReadOnly);

      while(file.readLineInto(&line))
      {
      Cell[0] = line.mid(0,line.indexOf("\t"));
      line.remove(0,(line.indexOf("\t")+1));
      Cell[1] = line;
      ui->tableWidget->insertRow(row);
      ui->tableWidget->item(row,0)->setText(Cell[0]);
      ui->tableWidget->item(row,1)->setText(Cell[1]);
      row++;
      }

   fclose(fp);
   }

jsulm

@dcbdbisVA You did not set any items in the new row, so I guess ui->tableWidget->item(row,0) and ui->tableWidget->item(row,1) both return null pointer. See http://doc.qt.io/qt-5/qtablewidget.html#insertRow : "Inserts an empty row into the table at row."
You need to set items in both columns using http://doc.qt.io/qt-5/qtablewidget.html#setItem

jsulm

@dcbdbisVA One note: if you use Qt you can use QFile to access files.

VRonin

ui->tableWidget->item(row,0) and ui->tableWidget->item(row,1) are null pointers.

QAbstractItemModel* model=ui->tableWidget->model();
QFile fp("Procedures.txt");
if(fp.open(QIODevice::ReadOnly | QIODevice::Text)){
QTextStream file(&fp);
for(;file.readLineInto(&line);++row){
const QStringList cells=line.split("\t");
model->insertRow(row);
model->setData(model->index(row,0),cells.value(0));
model->setData(model->index(row,1),cells.value(1));
}
fp.close();
}

P.S.
Yes, I hate the QStandardItem interface!

dcbdbisVA

VRonin and jsulm, THANK YOU.

I appreciated the code example VRonin....As you can tell by my style, I'm older. Think ENIAC, 300 baud acoustically coupled modems, and everything written in assembler.

I modified my code accordingly and it works perfectly.

To assist myself in the future when I read the docs, I would like to ask this question:

Where in the QT docs would I have gotten the model interface? When I was reading the class documentation, nowhere did it tell me about the model interface. I ASSumed that the class documentation had all I needed there. Contrasting QT to wxWidgets, and the VLC (from the Borland days) all fully documented their classes on how to interact with them. Frankly, I would not have gotten your solution from the QT docs themselves. So I am very appreciative for your example.

Is there some doc that I need to read elsewhere to brush-up on the "model" interface, and when to use/deploy it?

Thank You!

Dave

VRonin

QTableWidget is an unsusual animal, it's just a QTableView with a QStandardItemModel as a member.

In one of the see also in the documentation it links to http://doc.qt.io/qt-5/model-view-programming.html that explains that models must respect the QAbstractItemModel interface so you can use that one to manipulate models