Instanting Q_GADGET

[VRonin]

Hi everyone, http://doc.qt.io/qt-5/qtqml-cppintegration-data.html#value-types describes that Q_GADGET objects are available in QML but there is no example of how to use them in QML (there's only a C++ snippet).
Could you tell me how to create an instance of the Actor class defined in the documentation in QML/Javascript?
Thanks in advance

[sierdzio]

4 years later... but I have stumbled upon this topic and I have an answer, so maybe it will help somebody.

@VRonin said in Instanting Q_GADGET:

Could you tell me how to create an instance of the Actor class defined in the documentation in QML/Javascript?

You cannot instantiate Q_GADGETs in QML. But you can pass them from C++ into QML in 2 ways:

• via a property of another Q_OBJECT (this way you can even pass a default-constructed gadget, which is practically 100% the same as if you instantiated it in QML)
• via signal

For example:

class Gadget 
{
  Q_GADGET
  Q_PROPERTY(QString data MEMBER data)

public:
  QString data;
}

Q_DECLARE_METATYPE(Gadget)

class Object 
{
  Q_OBJECT
  Q_PROPERTY(Gadget gadget READ gadget)

public:
  Gadget gadget() { 
    Gadget result;
    return result;
  }
}

// QML:
Object {
  id: myObject

  Component.onCompleted: console.log("Gadget data is:", gadget.data)
}

[devel]

C++:

class MyValueType
{
    Q_GADGET
    QML_VALUE_TYPE(myValueType)
    QML_CONSTRUCTIBLE_VALUE
public:
    Q_INVOKABLE MyValueType(double d = 0.0);

    // ...
};

QML:

import MyModule as MM

QtObject {
    function process(d: real) {
        let v = new MM.myValueType(d);
        // v is a myValueType now
    }
}