[SOLVED] noob in qml / c++ unable to bind method return to onClicked event: TypeError Object [object Object] has no method XXXXXX

dhevans79

Hi all,

First, thanks for looking, and possibly responding to help me make a start with this development tool.

I'm trying to do a test where I use a QML window with a button to change the text of the button with the results of the function QString returnComplete(). However, even though the autocomplete shows me the method name, I get the error: TypeError: Object [object Object] has no method 'returnComplete'

Please see the code snippets below for more info. Please let me know if you need more...

backupplugin.h
@
#include <QTime>
#include <QString>

#ifndef BACKUPPLUGIN_H
#define BACKUPPLUGIN_H

class Backup : public QObject{
Q_OBJECT

Q_INVOKABLE QString returnComplete();
Q_INVOKABLE int returnOne();

};

#endif // BACKUPPLUGIN_H
@

backupplugin.cpp
@
#include "backupplugin.h"

QString Backup::returnComplete()
{
return QString("test complete");
}

int Backup::returnOne() {
return 1;
}
@

main.cpp
@qmlRegisterType<Backup>("testNamespace", 1, 0, "MyBackup");@

main.qml
@Page {
title: i18n.tr("Simple Backup")

    Backup {
        id: testBackup
    }
    ....
    //Start Button
            Row {
                width: parent.width
                Button {
                    id: btnStart
                    objectName: "btnStart"
                    width: parent.width

                    text: i18n.tr("Start Backup!")
                    onClicked: btnStart.text = MyBackup.returnComplete();

                }
            }

@

I have also tried (what I think to be correct, but I do not get any autocomplete options that match the function name...)

@onClicked: btnStart.text = testBackup.returnComplete();@

but then I get the error:
TypeError: Object Backup_QMLTYPE_36(0xddf660) has no method 'returnComplete'

Whatever I try, I am unable to get the return value from the c++ function.

please help, several hours of walking through the many, many examples on google searches, qt forums, BB forums, c++ forums, etc and I am unable to run a simple "hello world" POC for this stuff.

Thanks and regards,

David

sierdzio

In your main.cpp:
@
QQuickView *myView; // or whatever you are using to display your QML code
Backup *myBackup = new Backup();
myView->rootContext->setContextProperty("MyBackup", myBackup);
@

Then your code should work with:
@
onClicked: btnStart.text = MyBackup.returnComplete();
@

You can delete those lines, they are not needed:
@
// C++
qmlRegisterType<Backup>("testNamespace", 1, 0, "MyBackup");

// QML
Backup {
id: testBackup
}
@

dhevans79

Sierdzio,

Thanks for your reply. Unfortunately it doesn't work for me.

I have made the updates as you indicate, and I still get the same message:
TypeError: Object Backup(0x113c410) has no method 'returnComplete'

Just to confirm some details, as there were some differences I needed to make...

I'm using QT 5 on Ubuntu 12.10 with QtQuick 2
The window viewer is of type QtQuick2ApplicationViewer, however by using the autocomplete, it modified the line to:
@viewer.rootContext()->setContextProperty("MyBackup", myBackup);@

Sorry that it didn't work out, thanks for any further suggestions. I can zip the project for you if that would help???

sierdzio

Ah, huh, ok. I've missed an obvious part. Methods are private by default in C++... so your method is not visible to QML engine or MOC :D
just add "public:" to your code, after the Q_OBJECT macro:
@
class Backup : public QObject{
Q_OBJECT
public:
Q_INVOKABLE QString returnComplete();
Q_INVOKABLE int returnOne();

};
@

dhevans79

Doh!

Thank you for that, that was the trick. My apologies for such an obvious blunder...

Many regards,

David

sierdzio

No problem, very often it's the small and obvious detail like this :) Happens all the time to everybody ;)