How to reset a custom model?

Mr Gisa

I have a custom model that I'm studying and I was wondering, how can I reset the model and empty the items on the model and on the table view?

#ifndef RESULTSMODEL_HPP
#define RESULTSMODEL_HPP

#include <QAbstractTableModel>

class Result;

class ResultsModel : public QAbstractTableModel
{
    Q_OBJECT

public:
    explicit ResultsModel(QObject *parent = nullptr);

    int rowCount(const QModelIndex &parent) const override;
    int columnCount(const QModelIndex &parent) const override;
    QVariant data(const QModelIndex &index, int role) const override;
    bool setData(const QModelIndex &index, const QVariant &value, int role) override;
    QVariant headerData(int section, Qt::Orientation orientation, int role) const override;
    Qt::ItemFlags flags(const QModelIndex &index) const override;

    void addResult(Result *result);

private:
    QList<Result *> mResults;
};

#endif // RESULTSMODEL_HPP

The model holds the parenting of the Result * but I wanted that when resetting to delete the pointers as well.

Christian Ehrlicher

And what prevents you from deleting the pointer by yourself?
Make sure you call the functions beginResetModel/endRestModel as described in the documentation: http://doc.qt.io/qt-5/qabstractitemmodel.html#beginResetModel

Mr Gisa

That is the thing, I never did the beginResetModel and I read the docs but I couldn't find an example of the usage, where to call that and so on.

I tried like this but it's crashing:

void ResultsModel::reset()
{
    beginResetModel();
    qDeleteAll(mResults);
    endResetModel();
}

JKSH

@Mr-Gisa said in How to reset a custom model?:

I tried like this but it's crashing:

void ResultsModel::reset()
{
    beginResetModel();
    qDeleteAll(mResults);
    endResetModel();
}

After you call qDeleteAll(), you now have a QList full of dangling pointers.

See http://doc.qt.io/qt-5/qtalgorithms.html#qDeleteAll : "Notice that qDeleteAll() doesn't remove the items from the container; it merely calls delete on them. In the example above, we call clear() on the container to remove the items."

@Mr-Gisa said in How to reset a custom model?:

how can I reset the model and empty the items on the model and on the table view?

You're almost there. You just need to remove the dangling pointers. The basic steps for all models are:

Call beginResetModel() to tell the views to stop reading your model
Use your custom code to reset the internal data
Call endResetModel() to tell the views that the model has been reset. The views will now re-read the model to discover the updated data.

Mr Gisa

@JKSH

Use your custom code to reset the internal data

I tried to use mResults.clear() it worked but now I get a lot of pointers leaking.

I can't call qDeleteAll(mResults) cause the list is empty.

    beginResetModel();
    mResults.clear();
    endResetModel();

    qDeleteAll(mResults); // won't work.

JKSH

@Mr-Gisa said in How to reset a custom model?:

I tried to use mResults.clear() it worked but now I get a lot of pointers leaking.

I can't call qDeleteAll(mResults) cause the list is empty.

See the example code in the documentation. I provided the link in the previous post.

Mr Gisa

Oh gosh, sorry, I though that you mentioned only that part of the documentation and wasn't anything there other than that, my bad
It solved, thank you very much.

gabizzz

import QtQuick 2.11
import QtQuick.Window 2.11

Window {

id: window
visible: true
width: 300
height: 480
color: "#050122"
title: qsTr("sortea numeros")   

Grid{
    spacing: 1
    rows: 3
    columns: 2
    anchors.fill: parent

    Repeater {
        id:modelo
            model: 6
            delegate: Rectangle {
                  width: window.width/6;
                  height: window.height/6;
                  color: "darkblue";
                        Text {
                            anchors.centerIn: parent
                            font.pixelSize: 20
                            text: sortea()
                        }
                }
    }
}


MouseArea {
    id: mouseArea
    x: 220
    y: 387
    anchors.fill: parent
    onClicked: {
        modelo.model=0;
        modelo.model=6;
    }
}

function sortea()
{
    var random =Math.floor(Math.random() * 6) + 1;
    return random;
}

}