How can I access QAbstractTableModel Data from QML Repeater - c++

Question

I've been struggling for a few days trying to figure out how to display some pretty simple data in a QML window. I realize there are many ways to accomplish this task, and in this case, I'd prefer to find out how to use QAbstractTableModel.
I have a row of data, each row containing two items, a name and a value (name/value or key/value pair). I've subclassed the QAbstractTableModel to pass this data to the QML. Here is the code I have so far; it is mostly based on the tutorial that can be found here (which is also very old): https://doc.qt.io/archives/4.6/itemviews-addressbook.html.
databridge.h
#include <QObject>
#include <QAbstractTableModel>
#include <QPair>
class DataBridge : public QAbstractTableModel
{
Q_OBJECT
public:
explicit DataBridge();
explicit DataBridge(QList<QPair<QString, QString>> listOfPairs);
int rowCount(const QModelIndex &parent) const;
int columnCount(const QModelIndex &parent) const;
QVariant data(const QModelIndex &index, int role) const;
bool setData(const QModelIndex &index, const QVariant &value, int role);
QVariant headerData(int section, Qt::Orientation orientation, int role) const;
bool insertRows(int row, int count, const QModelIndex &parent);
bool removeRows(int row, int count, const QModelIndex &parent);
Qt::ItemFlags flags(const QModelIndex &index) const;
QList<QPair<QString, QString>> getList();
signals:
public slots:
private:
QList<QPair<QString, QString>> m_listOfPairs;
};
#endif // DATABRIDGE_H
databridge.cpp
#include "databridge.h"
DataBridge::DataBridge()
{}
DataBridge::DataBridge(QList<QPair<QString, QString> > listOfPairs)
{ m_listOfPairs = listOfPairs; }
int DataBridge::rowCount(const QModelIndex &parent) const
{
Q_UNUSED(parent);
return m_listOfPairs.size();
}
int DataBridge::columnCount(const QModelIndex &parent) const
{
Q_UNUSED(parent);
//Number of columns is always 2 in this kata
return 2;
}
QVariant DataBridge::data(const QModelIndex &index, int role) const
{
if(!index.isValid())
return QVariant();
if(index.row() >= m_listOfPairs.size() || index.row() < 0)
return QVariant();
if(role == Qt::DisplayRole)
{
QPair<QString, QString> pair = m_listOfPairs.at(index.row());
if(index.column() == 0)
return pair.first;
else
return pair.second;
}
return QVariant();
}
bool DataBridge::setData(const QModelIndex &index, const QVariant &value, int role)
{
//TODO
return QVariant();
}
QVariant DataBridge::headerData(int section, Qt::Orientation orientation, int role) const
{
//TODO
return QVariant();
}
bool DataBridge::insertRows(int row, int count, const QModelIndex &parent)
{
//TODO
return true;
}
bool DataBridge::removeRows(int row, int count, const QModelIndex &parent)
{
//TODO
return true;
}
Qt::ItemFlags DataBridge::flags(const QModelIndex &index) const
{
if(!index.isValid())
return Qt::ItemIsEnabled;
return QAbstractTableModel::flags(index) | Qt::ItemIsEditable;
}
QList<QPair<QString, QString> > DataBridge::getList()
{
return m_listOfPairs;
}
main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QPair>
#include "databridge.h"
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
QList<QPair<QString, QString>> inserter;
inserter.append(QPair<QString, QString>("0", "zero"));
inserter.append(QPair<QString, QString>("1", "one"));
inserter.append(QPair<QString, QString>("2", "two"));
inserter.append(QPair<QString, QString>("3", "three"));
inserter.append(QPair<QString, QString>("4", "four"));
DataBridge * bridge = new DataBridge(inserter);
engine.rootContext()->setContextProperty("bridge", bridge);
engine.load(QUrl(QLatin1String("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
return -1;
return app.exec();
}
main.qml
import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3
ApplicationWindow {
visible: true
width: 640
height: 480
title: qsTr("Hello World")
Component{
id: myComponent
Row{
id: thisRow
Text{
text: bridge.data(index, 0)
}
Text{
text: "\t.\t.\t.\t"
}
Text{
text: bridge.data(index, 0)
}
}
}
Column{
id: thisColumn
anchors.horizontalCenter: parent.horizontalCenter
Repeater{
id: myRepeater
delegate: myComponent
model: bridge
}
}
Component.onCompleted: {
console.log("DEBUG main.qml");
}
}
Please ignore the functions with TODO in them in the databridge.cpp. I didn't include the bodies for the sake of brevity.
The first problem I'm facing is that when my repeater in the main.qml calls bridge.data(index, 0), the index is determined to be invalid in the first if statement of the data function (if(!index.isValid()). I'm not sure why this is happening. The second issue I can see, though I haven't gotten that far yet, is how can I tell the data function if I'm calling column 0 or column 1? It checks for this later in the function, and returns the pair relevant to the column requested. I'm guessing that in myComponent, I need something more specific to request the data from whichever column, but I'm not sure what that would be?
Any help with this would be immensely appreciated. Thank you in advance!
QModelIndex Documentation
Another link to the example referenced at the top
QAbstractTableModel Documentation
Qt Role Enum Documentation

Answer 1

I was able to find a solution, but I'm not sure if it's the correct one. I've added a function to the databridge class that takes integer input from the QML, finds a corresponding QModelIndex, and pulls the data from the model that way. This is what the code looks like:
From databridge.cpp
QString DataBridge::getThisItem(int index, int column)
{
QModelIndex currentIndex = QAbstractTableModel::index(index, column);
QString retVal = data(currentIndex, 0).toString();
return retVal;
}
Corresponding QML Repeater Change
Component{
id: myComponent
Row{
id: thisRow
Text{
text: bridge.getThisItem(index, 0)
}
Text{
text: "\t.\t.\t.\t"
}
Text{
text: bridge.getThisItem(index, 1)
}
}
}
This produces the desired output, that being:
I am interested to know if this is a good implementation, or if there is a better way to do this. Thanks again!