[SOLVED]"TypeError: Object [object Object] has no method" w/ qmlRegisterType

[Tory Gaurnier]

I'm pretty certain this is the correct thread to post this in. First let me say, I'm very new to QT and QML, I've been working on an app in C and GTK, but for various reasons decided to switch to QML, figuring out how to combine C and C++ was easy enough, what I've had the most difficulty with is creating my Makefile, however after a few days I've gotten that all figured out (I didn't want to use qmake, so I figured out how to manually do a Makefile), my program compiles fine, and my QML gui shows, however when using qmlRegisterType I can't call methods from C++ in QML.

Ok, here is my gui.h:
@#ifdef __cplusplus
#include <QGuiApplication>
#include <QQuickView>
#include <QtQml>

class QmlConnect : public QObject {
Q_OBJECT
Q_PROPERTY(QString* getData READ getData)

public:
QmlConnect() {

}
Q_INVOKABLE QString* getData() {
static QString data_list[] = {"Data1", "Data2", "Data3", "Data4"};
return data_list;
}
};
#endif

#ifdef __cplusplus
extern "C" {
#endif
void gui_Init(int argc, char **argv);
#ifdef __cplusplus
}
#endif@

Here is my gui.cpp:
@#include "gui.h"

extern "C" {
#include "../globalvars.h"
#include "../library.h"
#include "../config.h"
#include "../misc.h"
}

void gui_Init(int argc, char **argv) {
QGuiApplication q_app(argc, argv);

// Connect QT C++ to QML
qmlRegisterType<QmlConnect>("QmlConnect", 1, 0, "QmlConnect");

// Start QML app
QQuickView view;
view.setSource(QUrl::fromLocalFile("gui.qml"));
view.show();

q_app.exec();
}@

And here's my gui.qml file:
@import QtQuick 2.0
import Ubuntu.Components 0.1
import Ubuntu.Components.ListItems 0.1 as ListItem

import QmlConnect 1.0

MainView {
objectName: "mainView"
applicationName: "MyApp"
id: root

width: units.gu(100)
height: units.gu(80)

property real margins: units.gu(2)
property real buttonWidth: units.gu(9)

Column {
id: libraryColumn
ListItem.Header {text: "Library"}
ListItem.Standard {text: "Section1"}
ListItem.Standard {text: "Section2"}
ListItem.Divider {}
ListItem.Header {text: "Lists"}

width: units.gu(10)
anchors {
left: parent.left
top: parent.top
bottom: parent.bottom
}
}
Grid {
Component.onCompleted: {
var data = QmlConnect.getData();
for(var i = 0; i < data.length; i++) {
console.log(data[i]);
}
}
}
}@

Now what's happening is when my QML file tries to call QmlConnect.getData() it throws the error "TypeError: Object [object Object] has no method 'getData'"

It doesn't fail to import the class itself, but it can't seem to call the mothod from the class. Any help is greately apprecieated.

[chrisadams]

Hi,

A couple of issues: your QmlConnect type isn't registered as a singleton type, so you need to instantiate an instance of it, in order to invoke a member function.

@
MainView {
id: root

QmlConnect {
    id: qmlconnect
}

// ....

Grid {
    Component.onCompleted: {
        var data = qmlconnect.getData()
        // ...
    }
}

}
@

Secondly, return a QStringList instead of a QString*. The overhead of passing core types by value is very low, as they use copy-on-write implicit sharing, and QML doesn't support returning (or interacting with) pointers unless they're QObject* (or QObject-derived*) - except wrapped in QVariants at which point they're opaque to QML anyway.

You can also use a Q_PROPERTY instead of a Q_INVOKABLE to be more declarative:

@
class QmlConnect : public QObject
{
Q_OBJECT
Q_PROPERTY(QStringList stringArray READ stringArray CONSTANT)

public:
QmlConnect(QObject *parent = 0);
~QmlConnect();

QStringList stringArray() const { QStringList retn; retn << "one" << "two" << "three"; return retn; }

};
@

Then in the qml, instead of calling getData() just resolve stringArray:

@
Component.onCompleted: {
var data = qmlconnect.stringArray
// ....
}
@

Cheers,
Chris.

[Tory Gaurnier]

Your amazing!!! Thank you, now I can move on with my project :D See I'm not even that familiar with C++, I don't even know what a singleton is :P Luckily the amount of C++ going into this will be minimal it's just to get variables from my C functions and pass them along to the QML, and vice versa.

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