I've created a custom type inside my Qt 5.2 qml application
class Setting : public QObject
{
Q_OBJECT
Q_PROPERTY(QString key READ key WRITE setKey)
Q_PROPERTY(QVariant value READ value WRITE setValue)
public:
Setting(QObject * parent = 0);
QString key() const;
void setKey(QString const & key);
QVariant value() const;
void setValue(QVariant const & value);
private:
QString m_key;
QVariant m_value;
};
and registered it in my main function:
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
qmlRegisterType<Setting>("Setting", 1,0, "Setting");
// ...
}
In my application I would like to have a button that has a signal with my custom type as a parameter:
import Setting 1.0
Button
{
signal settingChanged(string, Setting)
// ...
}
Every time I hit the button the signal should be emitted.
If I try to connect my qml signal with my C++ slot
QObject::connect(myButton, SIGNAL(settingChanged(QString, Setting)), this, SLOT(settingChanged(QString, Setting)));
Qt says
QObject::connect: No such signal Button_QMLTYPE_41_QML_45::settingChanged(QString, Setting) in ...
If I remove my custom type from the signal definition
Button
{
signal settingChanged(string)
// ...
}
and modify the connect call
QObject::connect(myButton, SIGNAL(settingChanged(QString)), this, SLOT(settingChanged(QString)));
the connect call worked.
I could use my custom qml type Setting inside the qml part of my application. But what I do wrong if I would like to use it with my signal settingChanged?
Thanks!
After I've readed the Qt documentation very carefully, I've found the answer here
The documentation says
When a QML object type is used as a signal parameter, the parameter should use var as the type, and the value should be received in C++ using the QVariant type.
So, the signal definition inside the qml description of Setting has to be replaced with var.
import Setting 1.0
Button
{
signal settingChanged(string, var)
// ...
}
To connect the qml signal with the C++ slot, the code has to be
Object::connect(myButton, SIGNAL(settingChanged(QString, QVariant)), this, SLOT(settingChanged(QString, QVariant)));
At this point the connection worked!
To make the whole thing running, the QVariant has to be casted to the right type inside the slot. In my case to a Setting type.
void Foo::settingChanged(QString name, QVariant const & var)
{
Setting * setting = qobject_cast<Setting*>(var.value<QObject*>());
// ...
}
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