Exposing QList<customobj *> to QML - c++

Question

I am trying to expose QList with custom objects (Sample) into QML. Whenever I store those custom objects (they inherits form QObject) into QList<QObject *>, they show up, but without info, but when I try expose them as a QList<Sample *>, they don't.
sample.h
class Sample : public QObject
{
Q_OBJECT
Q_PROPERTY(QString getVar READ getVar WRITE setVar NOTIFY varChanged)
public:
explicit Sample();
//! Returns var
QString getVar() const { return var; }
//! Sets var
void setVar(const QString &a);
signals:
varChanged();
protected:
QString var;
};
Class containing list looks like this
samplecontrol.h
class SampleManager : public QObject
{
Q_OBJECT
Q_PROPERTY(QList<Sample *> getSampleList READ getSampleList NOTIFY sampleListChanged)
public:
SampleManager(const QString &path);
//! Returns sample list
QList<Sample *> getSampleList() const { return sampleList_; }
signals:
sampleListChanged();
protected:
QList<Sample *> sampleList_;
};
I am setting context with
view_->rootContext()->setContextProperty("slabGridModel", QVariant::fromValue(samplecontrol.getSampleList()));
As I said, when i tired
QList<QObject *> datalist;
datalist.append(sampleManager.getSampleList().first());
datalist.append(sampleManager.getSampleList().last());
it worked. How can I make it work with QList<Sample *>?
Thanks for your help!

Answer 1

You can pass a list of QObjects, but the problem is that it will not notify the view if more elements are added, if you want the view to be notified you must use a model that inherits from QAbstractItemModel. On the other hand how are you doing the datamodel as qproperty it is better to expose the SampleManager:
samplemodel.h
#ifndef SAMPLEMODEL_H
#define SAMPLEMODEL_H
#include "sample.h"
#include <QAbstractListModel>
class SampleModel : public QAbstractListModel
{
Q_OBJECT
public:
using QAbstractListModel::QAbstractListModel;
~SampleModel(){
qDeleteAll(mSamples);
mSamples.clear();
}
int rowCount(const QModelIndex &parent = QModelIndex()) const override{
if (parent.isValid())
return 0;
return mSamples.size();
}
QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override{
if (!index.isValid())
return QVariant();
if(role == Qt::UserRole){
Sample *sample = mSamples[index.row()];
return QVariant::fromValue(sample);
}
return QVariant();
}
void appendSample(Sample * sample)
{
beginInsertRows(QModelIndex(), rowCount(), rowCount());
mSamples << sample;
endInsertRows();
}
QHash<int, QByteArray> roleNames() const{
QHash<int, QByteArray> roles;
roles[Qt::UserRole] = "sample";
return roles;
}
private:
QList<Sample *> mSamples;
};
#endif // SAMPLEMODEL_H
samplemanager.h
#ifndef SAMPLEMANAGER_H
#define SAMPLEMANAGER_H
#include "samplemodel.h"
#include <QObject>
class SampleManager : public QObject
{
Q_OBJECT
Q_PROPERTY(SampleModel* model READ model WRITE setModel NOTIFY modelChanged)
public:
using QObject::QObject;
SampleModel *model() const{
return mModel.get();
}
void setModel(SampleModel *model){
if(mModel.get() == model)
return;
mModel.reset(model);
}
signals:
void modelChanged();
private:
QScopedPointer<SampleModel> mModel;
};
#endif // SAMPLEMANAGER_H
main.cpp
#include "samplemanager.h"
#include "samplemodel.h"
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QTime>
#include <QTimer>
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
SampleManager manager;
manager.setModel(new SampleModel);
// test
QTimer timer;
QObject::connect(&timer, &QTimer::timeout, [&manager](){
manager.model()->appendSample(new Sample(QTime::currentTime().toString()));
});
timer.start(1000);
QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty("manager", &manager);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
return -1;
return app.exec();
}
main.qml
import QtQuick 2.9
import QtQuick.Window 2.2
Window {
visible: true
width: 640
height: 480
title: qsTr("Hello World")
GridView {
anchors.fill: parent
model: manager.model
delegate:
Rectangle {
width: 100
height: 100
color: "darkgray"
Text {
text: sample.getVar
anchors.centerIn: parent
}
}
}
}
The complete example can be found in the following link.