The model inherited from QAbstractTableModel throws errors

[Mikeeeeee]

Hi!
The model inherited from QAbstractTableModel throws errors : invalid new-expression of abstract class type 'MyModel'
How do I fix this error?

class MyModel : public QAbstractTableModel
{
    Q_OBJECT
public:
    enum Roles {
        Role1 = Qt::UserRole + 1,
        Role2,
        Role3
    };

    MyModel(QObject *parent = 0);

    void addRow(QString str1, QString str2, QString str3);

    int rowCount(const QModelIndex & parent = QModelIndex()) const;

    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;

protected:
    QHash<int, QByteArray> roleNames() const;
private:
    QList <QString> list1, list2, list3;
};

#include "mymodel.h"

MyModel::MyModel(QObject *parent)
    : QAbstractTableModel(parent)
{
}

void MyModel::addRow(QString str1, QString str2, QString str3)
{
    list1.append(str1);
    list2.append(str2);
    list3.append(str3);
}

int MyModel::rowCount(const QModelIndex & parent) const {
    Q_UNUSED(parent);
    return list1.count();
}

QVariant MyModel::data(const QModelIndex & index, int role) const {
    if (index.row() < 0 || index.row() >= list1.count())
        return QVariant();

    if(index.column() == 0){
        return list1[index.row()];
    }
    if(index.column() == 1){
        return list2[index.row()];
    }
    if(index.column() == 2){
        return list3[index.row()];
    }
    return QVariant();
}

QHash<int, QByteArray> MyModel::roleNames() const {
    QHash<int, QByteArray> roles;
    roles[Role1] = "role1";
    roles[Role2] = "role2";
    roles[Role3] = "role3";
    return roles;
}

[SGaist]

Hi,

Looks like you did not re-implement all the required methods.

Note that you are not implementing your addRow method correctly. You are missing the begin/endInsertRows call.

[Mikeeeeee]

I append this and now its normal and now it compiles normally

int MyModel::columnCount(const QModelIndex &parent) const
{
    return 3;
}

How to set the addRow() method correctly, now it looks like this:
void MyModel::addRow(QString str1, QString str2, QString str3)
{
beginInsertRows( QModelIndex(), 0, 2 );
list1.append(str1);
list2.append(str2);
list3.append(str3);
endInsertRows();
}

[Mikeeeeee]

And this model is not displayed in the table in QML:

class MyModel : public QAbstractTableModel
{
    Q_OBJECT

public:
    enum Roles {
        Role1 = Qt::UserRole + 1,
        Role2,
        Role3
    };

    MyModel(QObject *parent = nullptr);

    void addRow(QString str1, QString str2, QString str3);

    int columnCount(const QModelIndex &parent) const;

    int rowCount(const QModelIndex & parent = QModelIndex()) const;

    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;

protected:
    QHash<int, QByteArray> roleNames() const;
private:
    QList <QString> list1, list2, list3;
};

#include "mymodel.h"

MyModel::MyModel(QObject *parent) : QAbstractTableModel(parent)
{
    list1<<"11"<<"111"<<"1111";
    list2<<"22"<<"222"<<"2222";
    list3<<"33"<<"333"<<"3333";
}

void MyModel::addRow(QString str1, QString str2, QString str3)
{
    beginInsertRows( QModelIndex(), 0, 2 );
    list1.append(str1);
    list2.append(str2);
    list3.append(str3);
    endInsertRows();
}

int MyModel::columnCount(const QModelIndex &parent) const
{
    return 3;
}

int MyModel::rowCount(const QModelIndex & parent) const {
    Q_UNUSED(parent);
    return list1.count();
}

QVariant MyModel::data(const QModelIndex & index, int role) const {
    if (index.row() < 0 || index.row() >= list1.count())
        return QVariant();

    if(index.column() == 0){
        return list1[index.row()];
    }
    if(index.column() == 1){
        return list2[index.row()];
    }
    if(index.column() == 2){
        return list3[index.row()];
    }
    return QVariant();
}

QHash<int, QByteArray> MyModel::roleNames() const {
    QHash<int, QByteArray> roles;
    roles[Role1] = "role1";
    roles[Role2] = "role2";
    roles[Role3] = "role3";
    return roles;
}

[Mikeeeeee]

Still, my code works. Only 2 and 3 columns are the same as 1. How do I fix this?

[SGaist]

Why did you make roleNames protected ?
It's a public method.

[Christian Ehrlicher]

And you should only return values for Qt::DisplayRole. And you should not delete your posts.

[Mikeeeeee]

Sorry, I accidentally deleted it and couldn't restore it. The column index is always 0. What is the bug and how to fix it?

#ifndef MYMODEL_H
#define MYMODEL_H

#include <QObject>
#include <QAbstractTableModel>
#include "QSize"
#include "QBrush"
#include "QFont"
#include "QTime"
#include <QAbstractListModel>
#include <QStringList>
#include "QDebug"

//class MyModel : public QSqlTableModel
//class MyModel : public QAbstractListModel
class MyModel : public QAbstractTableModel
{
    Q_OBJECT

public:
    enum Roles {
        Role1 = Qt::UserRole + 1,
        Role2,
        Role3
    };

    MyModel(QObject *parent = nullptr);

    Q_INVOKABLE void addRow(QString str1, QString str2, QString str3);

    Q_INVOKABLE int columnCount(const QModelIndex &parent) const;

    Q_INVOKABLE int rowCount(const QModelIndex & parent = QModelIndex()) const;

    Q_INVOKABLE QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;
    //QVariant data(const QModelIndex &index, int role) const;
    QHash<int, QByteArray> roleNames() const;

private:
    QList <QString> list1, list2, list3;
};

#endif // MYMODEL_H

#include "mymodel.h"

MyModel::MyModel(QObject *parent) : QAbstractTableModel(parent)
{
    list1<<"11"<<"111"<<"1111";
    list2<<"22"<<"222"<<"2222";
    list3<<"33"<<"333"<<"3333";
}

void MyModel::addRow(QString str1, QString str2, QString str3)
{
    beginInsertRows( QModelIndex(), 0, 2 );
    list1.append(str1);
    list2.append(str2);
    list3.append(str3);
    endInsertRows();
}

int MyModel::columnCount(const QModelIndex &parent) const
{
    return 3;
}

int MyModel::rowCount(const QModelIndex & parent) const {
    Q_UNUSED(parent);
    return list1.count();
}

QVariant MyModel::data(const QModelIndex & index, int role) const {
    if (index.row() < 0 || index.row() >= list1.count())
        return QVariant();

    qDebug()<<index.column()<<index.row();

    QString unswer = QString("row = ") + QString::number(index.row()) + "  col = " + QString::number(index.column());
    // строкой выше мы формируем ответ. QString::number преобразует число в текст
    return QVariant(unswer);

//    return QString("Row%1, Column%2")
//                       .arg(index.row() + 1)
//                       .arg(index.column() +1);

    if(index.column() == 0){
        return list1[index.row()];
    }
    if(index.column() == 1){
        return list2[index.row()];
    }
    if(index.column() == 2){
        return list3[index.row()];
    }
    return QVariant();
}

QHash<int, QByteArray> MyModel::roleNames() const {
    QHash<int, QByteArray> roles;
    roles[Role1] = "role1";
    roles[Role2] = "role2";
    roles[Role3] = "role3";
    return roles;
}

[Christian Ehrlicher]

@Mikeeeeee said in The model inherited from QAbstractTableModel throws errors:

What is the bug and how to fix it?

Christian Ehrlicher 18 minutes ago

And you should only return values for Qt::DisplayRole

[Mikeeeeee]

I fixed the code, there is no more error. But the column index is always zero. I don't understand how to fix this. Debag returns:
0 0
0 0
0 0
Model size of -3 is less than 0
0 1
0 1
0 1
0 2
0 2
0 2

[Mikeeeeee]

[Christian Ehrlicher]

@Mikeeeeee said in The model inherited from QAbstractTableModel throws errors:

I fixed the code

Please update your code in your example so we can see what you're doing.

[Mikeeeeee]

This post is deleted!

[Mikeeeeee]

@Christian-Ehrlicher I updated the code an hour ago. I didn't add anything after that.

[Mikeeeeee]

Maybe the problem is in QML?

import QtQuick 2.13
import QtQuick.Controls 1.4

Item {
    width: 380
    height: 680

    TableView {
        anchors.fill: parent
        TableViewColumn {
            role: "role1"
            title: "Column1"
            width: 100
        }
        TableViewColumn {
            role: "role2"
            title: "Column2"
            width: 100
        }
        TableViewColumn {
            role: "role3"
            title: "Column3"
            width: 100
        }
        model: myModel
    }

}

[Christian Ehrlicher]

Then you still did not read my comment about the Qt::DisplayRole. So stay on your own.

[Mikeeeeee]

I don't understand what you mean. Please answer in more detail and clearly.

[Mikeeeeee]

Its work

QVariant MyModel::data(const QModelIndex & index, int role) const {
    if (index.row() < 0 || index.row() >= list1.count())
        return QVariant();
    if(role == 0){
        return QVariant(list1[index.row()]);
    }
    if(role == 1){
        return QVariant(list2[index.row()]);
    }
    if(role == 2){
        return QVariant(list3[index.row()]);
    }
    return QVariant();
}