passing signal with parameters from qml to c++ - qt

Question

I dont know how to pass parameters from QML file to c++ file in Qt.
QML code:
import QtQuick 1.1
Rectangle{
id:loin
height: 272
width:480
property alias loguid:loginuid
signal sigHome()
Rectangle{
id:rect1
width:parent.width-80
height:24
TextInput {
id:loginuid
maximumLength: 16
width: maximumLength * 20
focus: false
validator: RegExpValidator { regExp: /\d+/ }
KeyNavigation.down: login1
}
}
Button{
id: login1
x: 195
y: 187
height:30;
focus:false
border.color:"black"
opacity: activeFocus ? 1.0 : 0.5
Text{
text:"LOGIN"
anchors.horizontalCenter:login1.horizontalCenter;
anchors.verticalCenter:login1.verticalCenter;
}
Keys.onReturnPressed: {
if(loginuid.text < 1000000000000000)
{
text1.opacity=0.1
error1.visible=true
errorText.text="\n enter valid 16 digit number\n"
errorOk.focus=true
loginuid.focus=false
}
else{
loginuid.focus=false
loin.sigHome()
}
}
}
}
c++ code:
#include <QApplication>
#include <QDeclarativeView>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
int uid;
QDeclarativeView view;
view.setSource(QUrl::fromLocalFile("main.qml"));
view.show();
return app.exec();
}
When I press the login button rect1.text content shud go to main.cpp file and uid in the main.cpp get dat value. Something like this uid=rect1.text.
How to do it?

Answer 1

I wouldn't try to listen for a QML signal from the C++ side. Calling a C++ method with arguments is much easier and achieves the same:
To do so you have to:
define a slot or invokable method accepting the required arguments
register the class carrying the method with the declarative engine
then you can set an instance of this class as a property of your root context and finally call this method from QML
This topic is also well covered in the official documentation.

Answer 2

Thanks, sebasgo, your response helped me. I used signals and slots to communicate.
I created a signal in main.qml.
signal info(string msg)
and in login page
else{
info(loginUid.text)
loginuid.focus=false
loin.sigHome()
}
and in main.cpp I connected it to d slot
main.cpp goes like this
#include <QtGui>
#include <QApplication>
#include <QDeclarativeView>
#include <QtDeclarative>
class DeclarativeView : public QDeclarativeView
{
Q_OBJECT
public:
DeclarativeView(const QUrl & source) : QDeclarativeView(source)
{
}
public slots:
void readText(QString quid)
{
qdebug<<quid;
}
};
#include "main.moc"
int main(int argc, char *argv[])
{
QString file = "main.qml";
QApplication app(argc, argv);
DeclarativeView view(QUrl::fromLocalFile(file));
QDeclarativeItem *item = qobject_cast<QDeclarativeItem *>(view.rootObject());
QObject::connect(item, SIGNAL(info(QString)), &view, SLOT(readText(QString)));
view.show();
return app.exec();
}

Answer 3

Create a GUI controller C++ class:
class UiController : public QObject
{
Q_OBJECT
public:
UiController();
virtual ~UiController();
public slots:
void cal_daysoff__onDoubleClicked(const QDate& date);
};
In QML file you define, say, a calendar control in which you connect a signal to a slot in the controller:
Calendar{
id: cal_daysoff
Layout.fillWidth: true
Layout.fillHeight: true
onDoubleClicked: UiController.cal_daysoff__onDoubleClicked(date)
}
In main file, when launching the QML interface, connect the interface to the controller:
#include "uicontroller.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QQmlApplicationEngine engine;
UiController control;
engine.rootContext()->setContextProperty("UiController", &control);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
return app.exec();
}