How to use a custom Qt C++ type with a QML slot?

Question

I want to use my C++ type registered in QML as parameter in QML slot. So I already have C++ signal which has QString type parameter:

emit newMessage(myString);

and QML slot:

onNewMessage: {
    console.log(myString);
}

Now I want to pass C++ type registered in QML as parameter of this slot. I found similar question , but I don't understand how I can use this vice versa. Any help will be useful.

Answer 1

So Lets say you wanted to pass a QObject derived file back and forth from C++ to QML via a signal/slot setup.

  class MyClass : public QObject
  {
      Q_OBJECT
  public:
      explicit MyClass(QObject *parent = 0);


  signals:
      void sendSignal(MyClass* anotherMyClass)
  public slots:
       void  send_signals()  {   emit sendSignal(this); }
  };

If you have a C++ type called MyClass which is a QObject-based type, and you successfully did

    qmlRegisterType<MyClass>("com.myapp", 1, 0, "MyClass");

Then In QML all you have to do is this:

  import QtQuick 2.0
  import com.myapp

  Item {
        MyClass {
              id: myInstance
              Component.OnCompleted: {
                  // connect signal to javascript function
                  myInstance.sendSignal.connect( myInstance.receiveSignal);
              }
              function receiveSignal(mySentObject) {
                      // here is your QObject sent via Signal
                      var  receivedObject = mySentObject;

                     // Now to send it back 
                    //  (will cause an endless loop)
                      myInstance.sendSignal(receivedObject);

                     //  or you could do this to perform 
                      // the same endless loop
                     receivedObject.send_signals();

                     //  or you could do this to perform 
                      // the same endless loop
                     receivedObject.sendSignal(myInstance)

               } 
      }
  }

Summary:

You can just send any QObject-derived object as long as its registered with the QML engine as the actual object, you just treat it like any other type in QML

Hope this helps