Data not displaying on the QTreeView, QTableView,QListView classes

[JonB]

@VRonin
That's why I said "might get away with". I know how fond you C++ people here are about using the stack instead of the heap if at all possible (whereas I am Python/PyQt and so just use the heap the whole time :) ), so I put that in in case someone complained, I did wonder about it. I'll just cross it through!

[thippu]

@JonB said in Data not displaying on the QTreeView, QTableView,QListView classes:

. (As per @VRonin below, just don't try that way, stick to new!)

Sure.

[thippu]

@JonB , @VRonin I want to learn model/view architecture, so I picked up the Book Qt 4 art of building to study and practice, went to 207 page for basic understanding and page 222 example I want to study and implement,

1. They have told to store the .csv file format like this :
   ’’title (column 1)’’, ’’title (column 2)’’, ...,’’title (column n)’’
   ’’value’’, ’’value’’, ..., ’’value’’
   ’’value’’, ’’value’’, ..., ’’value’’
   ’’value’’, ’’value’’, ..., ’’value’’
   if I store like this and do qDebug() on the QList object, which has all the values of lines, it is giving output "" "" so, I did change the format and stored like this with values :
   csv file:
   'Name', 'Address'
   'thippu', 'talacaverlayout'
   after this change, qDebug() did show file data.
2. output and Ui
   2)Not understanding why the data is not displaying on the Views.
   code AddressbookGui:

//csv file read method.
QStringList splitCSVLine(const QString& line)
{
bool inItem = false;
QStringList items;
QString item;
for (int pos = 0; pos < line.length(); pos++)
{
QChar c=line.at(pos);
if ( c == ’\’’) {
if (inItem) {
items.append(item);
item = "";
}
inItem = !inItem;
}
else
if (inItem) {
item += c;
}
}
return items;
}

//constructor
AddressbookModel::AddressbookModel(const QString& addresses,
QObject *parent): QAbstractTableModel(parent)
{
QStringList records = addresses.split(’\n’);
QStringList line;
foreach(QString record, records)
addressBook.append(splitCSVLine(record));
}


int AddressbookModel::rowCount(const QModelIndex &parent ) const
{
Q_UNUSED(parent);
return addressBook.count() - 2;
}


//rowCount method
int AddressbookModel::columnCount(const QModelIndex &parent ) const
{
Q_UNUSED(parent);
return addressBook.at(0).count();
}

//headerData method
QVariant AddressbookModel::headerData(int section,Qt::Orientation orientation, int role) const
{
if (orientation == Qt::Horizontal) 
{
if (role == Qt::DisplayRole) 
{
 return addressBook.at(0).at(section);
}
}
return QAbstractTableModel::headerData(section, orientation, role);
}


//data method
QVariant AddressbookModel::data(const QModelIndex &index,
int role) const
{
if (!index.isValid()) return QVariant();
QStringList addressRecord = addressBook.at(index.row()+1);
if (role == Qt::DisplayRole || role == Qt::EditRole) {
return addressRecord.at(index.column());
}
if (role == Qt::ToolTipRole) {
QString tip, key, value;
tip = "<table>";
int maxLines = addressRecord.count();
for (int i = 0; i < maxLines; i++) {
key = headerData(i, Qt::Horizontal, Qt::DisplayRole)
.toString();
value = addressRecord.at(i);
if (!value.isEmpty())
tip += QString("<tr><td><b>%1</b>: %2</td></tr>")
.arg(key, value);
}
tip += "</table>";
return tip;
}
return QVariant();
}

[VRonin]

1. pass your model through the Model Test
2. make sure it survives and doesn't go out of scope as your views did

[thippu]

@VRonin Yeah, I did that no errors, bro.
code what I did is: inside QWidget.

new QAbstractItemModelTester(model,QAbstractItemModelTester::FailureReportingMode::Fatal);

[JonB]

@thippu
As @VRonin asked, how do we know from the code you post what the scope/lifetime of your AddressbookModel instance is?

[thippu]

@JonB I did convert all the objects from stack memory to heap, I'm not getting what you need?

[thippu]

@JonB
And also I did modelTest, There was no error.

[thippu]

@JonB changed all to the heap, I think they will stay till application die, right?
code I have changed:

Widget::Widget(QWidget *parent)
: QWidget(parent)
{
QFile file("path");
if(!file.open(QIODevice::ReadOnly|QIODevice::Text))
{
qDebug()<<"can't access the file";
}
QString *addresses=new QString(QString::fromUtf8(file.readAll()));
Addressbookmodel *model=new Addressbookmodel(addresses,this);

QListView *listView=new QListView();
listView->setModel(model);
listView->setModelColumn(0);
listView->show();

QTreeView *treeView=new QTreeView;
treeView.setModel(model);
treeView.show();

QTableView *tableView=new QTableView;
tableView.setModel(model);
tableView.show();

setMiniumSize(800,400);
QVBoxLayout *Vlayout=new QVBoxLayout(this);
Vlayout->addWidget(listView);
Vlayout->addWidget(treeView);
Vlayout->addWidget(tableView);
}

[JonB]

@thippu

Addressbookmodel *model=new Addressbookmodel(addresses,this);
treeView.setModel(&model);
tableView.setModel(&model);

Now that model is a pointer, why the &s?

[thippu]

@JonB Sorry, typo mistake.

[thippu]

@JonB I did copy and paste from the early reply, So

[VRonin]

I'm surprised you don't get into stack overflow.
AddressbookModel::rowCount and AddressbookModel::columnCount form an infinitely deep tree.

You should return 0; if the parent argument isValid()

[thippu]

@VRonin okay,
In the Addressbookmodel.cpp
I changed the code to :

int Addressbookmodel::rowCount(const QModelIndex &parent) const
{
   if(parent.isValid())
{
  return 0;
}
return addressbook.count-2;
}


int Addressbookmodel::columnCount(const QModelIndex &parent)
const
{
  if(parent.isValid())
  {
   return 0;
  }
return addressbook.at(0).count();
}

I don't know why it is not used in the book and why am not getting data on the widgets still?.

[thippu]

@VRonin Can share me an example that helps me to understand how to create QTreeView model and subclass it?, so from this I can able to create my own models successfully.

[VRonin]

@thippu said in Data not displaying on the QTreeView, QTableView,QListView classes:

Can share me an example that helps me to understand how to create QTreeView model and subclass it?

http://doc.qt.io/qt-5/qtwidgets-itemviews-simpletreemodel-example.html

[thippu]

@VRonin , Thank you.