Qt: Connect list in c++ to listview in QML - c++

Question

I just started learning Qt. To be honest, some of confuses my a lot. I'm trying to load a predefined .csv table into a listview.
I created a qml file with the simple layout of a textfield, a listview and a button to load a file. The file looks like this:
import QtQuick 2.7
import QtQuick.Controls 2.2
import QtQuick.Layouts 1.3
import QtQuick.Dialogs 1.2
ApplicationWindow {
id: applicationWindow
objectName: "App"
visible: true
width: 640
height: 480
title: qsTr("Rosinenpicker")
ColumnLayout {
id: columnLayout
anchors.rightMargin: 40
anchors.leftMargin: 40
anchors.bottomMargin: 40
anchors.topMargin: 40
anchors.fill: parent
TextField {
id: name
text: qsTr("Text Field")
Layout.preferredHeight: 50
Layout.fillWidth: true
}
ListView {
id: list
x: 0
y: 0
width: 110
height: 160
spacing: 0
boundsBehavior: Flickable.DragAndOvershootBounds
Layout.fillHeight: true
Layout.fillWidth: true
objectName: "listView"
model: guestModel
delegate: Item {
x: 5
width: 80
height: 40
Text {
text: model.modeldata.name
font.bold: true
anchors.verticalCenter: parent.verticalCenter
}
}
}
Button {
id: button
width: 50
text: qsTr("Open File")
Layout.preferredWidth: 100
Layout.alignment: Qt.AlignRight | Qt.AlignVCenter
onClicked: fileDialog.visible = true;
}
FileDialog {
id: fileDialog
title: "Please choose a valid guestlist file"
objectName: "fileDialog"
nameFilters: ["Valid guestlist files (*.csv)"]
selectMultiple: false
signal fileSelected(url path)
onAccepted: fileSelected(fileDialog.fileUrl)
}
}
}
In my main file I create a CsvParser class a connect it to the fileSelected signal of the file dialog.
I can parse the csv-File. But when I try to connect it to the listview, I'm lost.
The main file:
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtDebug>
#include <QUrl>
#include <QQuickView>
#include "csvparser.h"
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
engine.load(QUrl(QLatin1String("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
return -1;
auto root = engine.rootObjects().first();
auto fileDialog = root->findChild<QObject*>("fileDialog");
CsvParser parser(engine.rootContext());
QObject::connect(fileDialog, SIGNAL(fileSelected(QUrl)), &parser, SLOT(loadData(QUrl)));
return app.exec();
}
My parser looks like this:
#include "csvparser.h"
#include <QtDebug>
#include <QFile>
#include "guest.h"
CsvParser::CsvParser(QQmlContext *context)
{
this->context = context;
}
void CsvParser::loadData(QUrl path)
{
friendList.clear();
guestList.clear();
QFile file(path.toLocalFile());
file.open(QIODevice::ReadOnly);
// ignore first lines
for(int i=0; i<3; i++)
file.readLine();
while(!file.atEnd()) {
auto rowCells = file.readLine().split(',');
if(rowCells.size() != 6)
continue;
checkedAdd(friendList, rowCells[0], rowCells[1]);
checkedAdd(guestList, rowCells[3], rowCells[4]);
}
qDebug() << guestList.size();
auto qv = QVariant::fromValue(guestList);
context->setContextProperty("guestModel", qv);
}
void CsvParser::checkedAdd(QList<QObject*> &list, QString name, QString familyName)
{
if(name == "" && familyName == "")
return;
list.append(new Guest(name, familyName));
}
And the guest, which has only a name and a familyname looks like this:
#ifndef GUEST_H
#define GUEST_H
#include <QObject>
class Guest : public QObject
{
public:
Q_OBJECT
Q_PROPERTY(QString name READ name WRITE setName NOTIFY nameChanged)
Q_PROPERTY(QString fName READ fName WRITE setfName NOTIFY fNameChanged)
public:
Guest(QString name, QString fName);
QString name();
QString fName();
void setName(QString name);
void setfName(QString fName);
signals:
void nameChanged();
void fNameChanged();
private:
QString m_name, m_fName;
};
#endif // GUEST_H
I get the following output:
qrc:/main.qml:41: ReferenceError: guestModel is not defined
QFileInfo::absolutePath: Constructed with empty filename
2
qrc:/main.qml:49: TypeError: Cannot read property 'name' of undefined
qrc:/main.qml:49: TypeError: Cannot read property 'name' of undefined
What am I doing wrong? Any help is appreciated. Thanks!

Answer 1

There are a few things I think are wrong. QML will not find guestModel, because it tries to render the ListView but it has not been made available to QML since you are setting the context property in loadData(), which is however only invoked when the user interacts with the FileDialog. Also, the Q_OBJECT macro needs to appear in the private section of the class (see http://doc.qt.io/qt-5/qobject.html#Q_OBJECT). Also, I do not think it is nice to make a data container/parser class aware of the UI, i.e. you export the rootContext to the parser. It would be better if you export something from the parser to the rootContext in main. The parser should have no notion of the UI IMHO. Finally, if you want to implement a custom list of data items to be displayed, you really should think about using an AbstractListModel as Yuki has suggested (see, http://doc.qt.io/qt-5/qabstractlistmodel.html) or another suitable List-based model (see, http://doc.qt.io/qt-5/qtquick-modelviewsdata-cppmodels.html). This way, changes in C++ will automatically result in updates in the UI.