Stop a signal from firing from code!

Kris Revi

this

void MainWindow::on_tableWidgetDeviceList_cellChanged(int row, int column)
{
}

gets fired when i populate the tableWidget within code! i ONLY want to fire this off when a USER changes a cell text! how?

i googled and found this

ui->tableWidgetDeviceList->blockSignals(true);

but did not work

Kris Revi

@mrjj ty :) got it working like this

void cellwasChanged(int row, int column);

connect(ui->tableWidgetDeviceList, &QTableWidget::cellChanged, this, &MainWindow::cellwasChanged);

void MainWindow::cellwasChanged(int row, int column)
{
    qDebug() << "Row : " << row << "Column : " << column;
}

but why is it when using the auto goto slot -> cellChanged code triggers that slot but doing it manu it doe not :S

mrjj

Hi

Best way to fix this is not to use the auto connect feature.
(GoOto Slot, and name on_tableWidgetDeviceList_cellChanged)

and simply use manual connect staement.

Then you first fill the table.
then you connect the slots.

No issues and better desgin. :)

Kris Revi

@mrjj ty :) got it working like this

void cellwasChanged(int row, int column);

connect(ui->tableWidgetDeviceList, &QTableWidget::cellChanged, this, &MainWindow::cellwasChanged);

void MainWindow::cellwasChanged(int row, int column)
{
    qDebug() << "Row : " << row << "Column : " << column;
}

but why is it when using the auto goto slot -> cellChanged code triggers that slot but doing it manu it doe not :S

mrjj

@Kris-Revi

but why is it when using the auto goto slot -> cellChanged code triggers that slot but doing it manu it doe not :S

That is simply the order.
Auto connected is run in setupUI() and you fill after

with manual connect you fill first, then connect.

So as non magical as it gets . :)

Kris Revi

@mrjj befor i mark this as solved! is it better to do manual connect on everything from buttons, sliders and so on then the "auto goto slot" then?!

JonB

@Kris-Revi
Yep! More powerful, less gotchas. That's just how it is. See how we are having a similar conversation at https://forum.qt.io/topic/128677/no-documents-matching-ui_form-h-could-be-found/9, with same recommendation though for specific gotcha-reason there.

Kris Revi

@JonB sweet :) i'll check it out! gonne remove all my auto goto slots and do them manualy :)

VRonin

For people ending up here from Google:
If you want a signal to be sent only when the user edits the cell and not when it's done by internal processes the correct way is a simple custom delegate:

class EditSignalDelegate : public QStyledItemDelegate {
Q_OBJECT
public:
using QStyledItemDelegate::QStyledItemDelegate ;
void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const override {
QStyledItemDelegate::setModelData(editor,model,index);
indexEdited(index);
}
signals:
void indexEdited(const QModelIndex &index);
};

Now you can use

EditSignalDelegate* delegate = new EditSignalDelegate(this);
connect(delegate,&EditSignalDelegate::indexEdited,this,[](const QModelIndex &index){qDebug() << "cell edited " << index.row() << "," <<index.column();});
ui->tableWidgetDeviceList->setItemDelegate(delegate);

Solved Stop a signal from firing from code!