How to modify the data in the model and update the view when new data is received from external?

[A Former User]

@VRonin: So now the test is running error free. This was the implementation i had to make:

QModelIndex Model::parent(const QModelIndex& index) const {
    if (!index.isValid()) {
        return QModelIndex();
    }

    if (isCategory(index)) {
        return QModelIndex();
    }

    const auto currentItem = static_cast<ScenarioPropertyItem*>(index.internalPointer());
    CategoryItem* parentItem = currentItem->parentItem();
    int rowNum = categories_.size();
    for (int i = 0; i < rowNum; i++) {
        if (categories_.at(i)->displayName() == parentItem->displayName()) {
            rowNum = i;
        }
    }
    return createIndex(rowNum, 0, parentItem);
}

But the view is still not displaying the new values. :( This is how i update the value

    QModelIndex index = createIndex(1, 1, categories_[0]->entryAt(0));
    this->setData(index, 11, Qt::EditRole);

My SetData:

bool Model::setData(const QModelIndex& index, const QVariant& value, int role /*= Qt::EditRole*/) {
    if (role == Qt::EditRole && index.column() == 1 && index.isValid()) {
        auto currentItem = static_cast<ScenarioPropertyItem*>(index.internalPointer());
        if (currentItem) {
            currentItem->setValue(value);
            emit dataChanged(index, index);
            return true;
        }
    }
    return false;
}

[VRonin]

@VInay123 said in How to modify the data in the model and update the view when new data is received from external?:

But the view is still not displaying the new values

Does the view display the old values or is it completely empty? is currentItem null?

[A Former User]

@VRonin: I initialize the model data i.e. categories_ with empty values. So the view shows empty value. But i update the value in my function and in debug mode i see the new value in the variable but the view shows empty i.e. old value. If i change the property to write mode, via delegate the value is being changed and view displays correctly. But when i do as following it does not:

    QModelIndex index = createIndex(1, 1, categories_[0]->entryAt(0));
    this->setData(index, 11, Qt::EditRole);

It actually calls the setData too and emits dataChanged. But the view is not displaying. Just for info my index method looks like this:

QModelIndex Model::index(int row, int column, const QModelIndex& parent /*= QModelIndex()*/) const {
    if (!hasIndex(row, column, parent)) {
        return QModelIndex();
    }

    if (!parent.isValid()) {
        return createIndex(row, column, categories_.at(row).get());
    }

    const auto currentCategory = static_cast<CategoryItem*>(parent.internalPointer());
    ScenarioPropertyItem* currentItem = currentCategory->entryAt(row);

    if (currentItem) {
        return createIndex(row, column, currentItem);
    } else {
        return QModelIndex();
    }
}

[VRonin]

What version of Qt are you on?
Usually the view ignores the dataChanged if it thinks the cell pointed by index shouldn't exist

[A Former User]

@VRonin : I use Qt5.9.0. The update should have been this

    QModelIndex index = createIndex(0, 1, categories_[0]->entryAt(0)); // but not 1,1
    this->setData(index, 11, Qt::EditRole);

But even then after the above change its not updating. Actually in setData there is already a index.isValid() check. The indexes looks good and also the currentItem. Should i post my model and view once again after the new changes i have done?

[VRonin]

@VInay123 said in How to modify the data in the model and update the view when new data is received from external?:

Actually in setData there is already a index.isValid() check.

index.isValid() is an insufficient check, that's why checkIndex was introduced in Qt 5.11

The indexes looks good and also the currentItem.

Unfortunately sometimes that's not enough. For example, if you forget to signal the view that you inserted a row, and then emit dataChanged for an item in that row, even if the item is 100% valid in the model the view will still think the row doesn't exist and do nothing

[A Former User]

@JonB @VRonin @SGaist : Something is not seeming right. I tried first to change the value using the following:

QModelIndex index = createIndex(0, 1, categories_[0]->entryAt(0));
    this->setData(index, 11, Qt::EditRole);

And in delegate class i tried to see what the value it has but it looks like it is zero. Below is the implementation:

QWidget *PropertyEditorItemDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const {
    if (!index.isValid()) {
        return nullptr;
    } else if (index.column() == 0) {
        return QStyledItemDelegate::createEditor(parent, option, index);
    }

    const auto currentItem = static_cast<ScenarioPropertyItem *>(index.internalPointer());
    switch (currentItem->itemType()) {
        case PropertyType::DOUBLE: {
            QDoubleSpinBox *box = new QDoubleSpinBox(parent);
            auto v = currentItem->data(index.column()); // Here it is zero??? :(
            box->setValue(v.toDouble());
            return box;  // qt will handle deletion
        }
default:
            return QStyledItemDelegate::createEditor(parent, option, index);
    }
}

[VRonin]

In setData could you add the qDebug as below and tell us what is printed?

if (currentItem) {
           currentItem->setValue(value);
qDebug() << currentItem->data(1);
qDebug() << index.data(Qt::DisplayRole);
             emit dataChanged(index, index);
             return true;
        }

[A Former User]

@VRonin :

[16:56:03,236] [Debug] QVariant(int, 11) / My new values
[16:56:03,237] [Debug] QVariant(int, 11) // My new values

;(
When i change via delegate:

[16:58:06,173] [Debug] QVariant(double, 0)
[16:58:06,176] [Debug] QVariant(double, 0)

I believe somewhere the indexes are not right. When i try to change the value(via delegate) of suppose "T" value so that i can iterate over parent and see the "S" value, here it is empty, but should be 11.

[A Former User]

My model looks like this:

In parent method i use pointer for parent item but not reference.

[A Former User]

@VRonin @SGaist @JonB : I just debugged to see that after changing the value of the property via delegate does the index in the following code has the same value.

QModelIndex index = createIndex(0, 1, categories_.at(0)->entryAt(0));
    this->setData(index, 11, Qt::EditRole);

But it turns out that the index in the above is just a copy and when delegate changes the value it is not reflected in the index here. I think i am changing at a copy of the property but not the actual one.

[A Former User]

This post is deleted!

[VRonin]

Can you show us the code for Delegate::setModelData?

[A Former User]

@VRonin

 void PropertyEditorItemDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const {
        const auto currentItem = static_cast<ScenarioPropertyItem *>(index.internalPointer());

        auto setup = [this, &model, &index](auto editor, auto usage) {
            if (editor) {
                usage(editor);
            } else {
                QStyledItemDelegate::setModelData(editor, model, index);
            }
        };

        switch (currentItem->itemType()) {
            case PropertyType::DOUBLE: {
                setup(qobject_cast<QDoubleSpinBox *>(editor), [&index, &model](QDoubleSpinBox *editor) {
                    editor->interpretText();
                    model->setData(index, editor->value(), Qt::EditRole);
                });
                break;
            }
            case PropertyType::INTEGER: {
                setup(qobject_cast<QSpinBox *>(editor), [&index, &model](QSpinBox *editor) {
                    editor->interpretText();
                    model->setData(index, editor->value(), Qt::EditRole);
                });
                break;
            }
            case PropertyType::STRING: {
                setup(qobject_cast<QLineEdit *>(editor), [&index, &model](QLineEdit *editor) { model->setData(index, editor->text(), Qt::EditRole); });
                break;
            }
            case PropertyType::BOOLEAN: {
                setup(qobject_cast<QComboBox *>(editor),
                      [this, &index, &model](QComboBox *editor) { model->setData(index, editor->currentText(), Qt::EditRole); });
                break;
            }
            default:
                QStyledItemDelegate::setModelData(editor, model, index);
                break;
        }
    }

[A Former User]

This post is deleted!

[SGaist]

Why are you calling createIndex in onRefreshRoadInfo ?

[A Former User]

@SGaist In onRefereshRoadInfo function i get the new values which has to be shown in the view. So, here I want to update the values, and as i dont have the index's, i create index for every property and call setData to update the values. If this is not correct how should i update the values here?

[A Former User]

@JonB @SGaist @VRonin : Any lead for my problem?

[SGaist]

Please show more patience, allow at least 24 hours before bumping your own thread. People answering on this forum do it on a voluntary basis and might not live in the same time zone as you.

That said, I stumble upon the QJsonModel project. You might want to check it.

[A Former User]

@SGaist I will keep in mind :). I saw the project and looks like my current implementation looks but, the project does not have the one thing i am looking for i.e. updating of data inside the code i.e. onRefereshRoadInfo.