[SOLVED] Passing a List of Urls from QML to C++ using a signal

onek24

Hey,

This documentations might help you out:
"Data Type Conversion Between QML and C++":http://qt-project.org/doc/qt-5.0/qtqml/qtqml-cppintegration-data.html
"QDeclarativeModels":http://qt-project.org/doc/qt-4.8/qdeclarativemodels.html

Korchkidu

Thanks for the links. I read it and it seems to me that I should pass a variant to my signal. Am I on the right track?

onek24

You're welcome. You can pass a variant as an array to Cpp, see:
"Variant":http://qt-project.org/doc/qt-4.8/qml-variant.html

But it looks like you can't set a list as a parameter for a signal. It may work if you set a var and then still pass the list to the signal on emit. Example:

@Rectangle{
property list<Rectangle> rectlist: [Rectangle{}]
signal emitMe(var)
onWidthChanged: emitMe(rectlist)
}@

Korchkidu

Thanks a lot!
This is actually what I did: I pass a variant, then get the QVariant in the C++ code, and convert it back to a QList<QUrl> and it works.

Thanks a lot for your help!

onek24

I'm glad that i could help you. :)

livelylama

Hi,
I ran into exactly same problem. I also have to pass the list<url> (fileUrls) from the FileDialog to C++. I did everything as you described above:

I define the signal using: @signal sendUrls(var variant)@

I send the signal using: @sendUrls(fileDialog.fileUrls)@

But in the C++ I only get an empty variant. If I pass the recieved variant into qDebug I get "QVariant(QList<QUrl>, )" as output.
So I dont actually recieve anything useful from the signal.
If I instead make the signal to transmit an integer and I send sendUrls(fileDialog.fileUrls.length) i recieve the integer and everything works fine.

So maybe you could tell me how exactly you managed to send the list<url> as a variant and how you then converted it to QList<QUrl>. Or maybe just post her that part of your code which deals with sending and receiving the the list<url> / Qvariant

I would be very grateful for any help.

onek24

Hello and welcome to devnet,

var and variant are both types, so i would say there is the problem. It's like you were trying to declare an int char = 0 in Cpp. Just write:
@signal sendUrls(var)@
or
@signal sendUrls(variant)@

livelylama

Hi thanks for your reply.
I changed the line now to @signal sendUrls(variant name)@

this doesn't solve my problem though. I still don't get a proper QVariant into my cpp code. I still get QVariant(QList<QUrl>, ) as output when I call @recieveUrllist(QVariant Urllist)
{
qDebug() << Urllist;
}
@

also I can't declare a signal without writing a name, so what you proposed to me
@signal sendUrls(variant)@

gives me an error: Expected token `identifier'

When i use
@signal sendUrls(variant name)@

or
@signal sendUrls(var name)@

i can compile it. The result stays the same whether i use var or variant.

So basically I want to pass my Urllist which I get from a filedialog into a c++ method so that I can use it there. If you know a way thats better then sending a variant via a signal i would be happy to hear it as well.

Thanks for your help so far,
It is much appreciated.

Xander84

just a question (and maybe solution), why do you need to define a signal in QML for this? can't you simply call the c++ slot and pass the URL list directly?

livelylama

Yes that works. I thought I had to use a signal because it was mentioned here in this forum. But it is much easier just to pass on the URLList right into a function as you say. It works very fine now.

With your reply of two lines you saved me a couple of hours of trail and error. Many thanks for that (: