[SOLVED] QWebKit Bridge - emiting a custom QList<Object> to a json array?

[maximus]

I have a custom QWidget that can emit a QList<Trackpoint> to my QWebView when a file is loaded.
The problem I have is that I'm not able to reconstruct the QList in the javascript slot. I would like to reconstruct a json array somehow.
I have tried with a QList<int> instead and it can reach my javascript code, but unable to do it with my custom Object.

A Trackpoint is just a custom Object with 3 fields:

    double lon;
    double lat;
    double elevation;

C++ Signal - void trackChanged(QList<Trackpoint>);

void GoogleMapWidget::on_loadCourse_clicked()
{
	QString file = QFileDialog::getOpenFileName(this, tr("Import Course"), "C:/Dropbox/VeloTest",
												tr("Course Files(*.gpx *.tcx *.kml)"));
	if (file.isEmpty())
		return;
	GpxParser gpxParser;
	gpxParser.parseFile(file);

	emit trackChanged(gpxParser.getLstTrackpoints());
}

Javascript slot

$(function() {

	var connected = false;
	function connectSlots() {
		if ( !connected ) {
			connected = true;
			googleMapWidget.trackChanged.connect(this, sayHello);
		}
	}

	connectSlots();
	//-----------------------
	function sayHello(coords) {
		alert(coords[0]); //the QList<Object> doesnt seem to get converted here, QList<int> works..
	}	
});

[maximus]

Another solution would be to parse the file in Javascript, but I already coded the function in C++ (QXmlReader..).
I also need to have access to the list of TrackPoint in the C++ code so i'd prefer to learn to how transport the data to the javascript layer correctly.

Example of use case:
https://www.dropbox.com/s/6pks6znbusjlctp/exampleMap.png?dl=0
1- User click "load course"
2- Course is parsed and shown in google map
...

Thanks

[maximus]

Anyone knows the best type of QList<?> I could use so that the QList get transformed to a json array automatically? is that even possible? My object is just 3 double.

[p3c0]

@maximus I'm not aware of any direct way to convert QList to JSON. Instead I used the following way to convert QList to QJsonArray in one of my projects. I have adjusted it

QJsonObject obj;
QJsonArray trackpoints;

foreach(Trackpoint* point,list) {
    QJsonObject obj;
    obj["lon"] = QString::number(point->getLon()); //add these methods in Trackpoint class
    obj["lat"] = QString::number(point->getLat());
    obj["elevation"] = QString::number(point->getElevation());
    trackpoints.append(obj);
}
obj["TrackPoints"] = trackpoints;
QByteArray b = QJsonDocument(obj).toJson(QJsonDocument::Indented);

Then once you get this JSON in the form of bytearray you can send it in the signal and parse it on JavaScript side.

[maximus]

Thanks @p3c0
I almost got it with your code. I just need to reparse the QbyteArray to a json array on the client side (javascript).
Still looking for a good way to do that
Here is what I have now :
https://www.dropbox.com/s/doc2zwu030f8e0g/alertMsg1.png?dl=0

Seems it is being sent as a "Uint8ClampedArray", but I have negative double in my data, so I should probably change this somehow..

Client slot

function sayHello(coords) {
    alert(coords + " length is:" + coords.length);
    //TODO: to parse this back to JsonArray
}

Qt

//Convert QList<Trackpoint> to QJsonArray
QJsonObject obj;
QJsonArray trackpoints;

foreach(Trackpoint tp, gpxParser.getLstTrackpoints()) {
    QJsonObject obj;
    obj["lon"] = QString::number(tp.getLon(), 'f', 8); //specify decimal for double?
    obj["lat"] = QString::number(tp.getLat());
    obj["elevation"] = QString::number(tp.getElevation());
    trackpoints.append(obj);
}
obj["TrackPoints"] = trackpoints;
QByteArray b = QJsonDocument(obj).toJson(QJsonDocument::Indented);
emit trackChanged(b);

[maximus]

Found a solution!

Apparently a QVariantList get transformed automatically to a Json Object, so this way worked for me without needing to parse:

Qt send signal with a QVariantList, get transformed auto

QJsonArray trackpoints;

foreach(Trackpoint tp, gpxParser.getLstTrackpoints()) {
    QJsonObject obj;
    obj["lon"] = tp.getLon();
    obj["lat"] = tp.getLat();
    obj["elevation"] = tp.getElevation();
    trackpoints.append(obj);
}
QVariantList variantLst = trackpoints.toVariantList();
emit trackChanged(variantLst);

Client Slot

function sayHello(coords) {
    alert(coords + " length is:" + coords.length);
    alert(coords[1]["lon"]);

[p3c0]

@maximus Well either that or since you are parsing it in JS you use JSON parser too. QWebView supports it. Here's an example to parse Json Array.