[Qt-qml] Q_INVOKABLE member function: Valid argument types

[Girish Ramakrishnan]

Hi Jonathan,
For multiple values, return a QVariantMap.

QVariantMap value;
value.setProperty("myOutputInt1", myOutputInt1);
value.setProperty("myOutputInt2", myOutputInt2);
return value;

And in the QML,
var myVariant = myClassObject.myFunc5();
var myInt1 = myVariant.myOutputInt1;
var myInt2 = myVariant.myOutputInt2;

You can also return a QVariantList for returning arrays.

Girish

On Wed, Oct 12, 2011 at 2:43 AM, Jonathan Zhong
<jonathan.zhong at panasonic.aero> wrote:
> Thanks! This is exactly the Qt documentation page I had been looking for. My
> prior experimentation appears to support what the documentation says.
>
> There is one remaining issue: Since int * as an argument does not appear
> working, what if I need to get more than one output integers from the
> Q_INVOKABLE function?
>
> That is, since the following may not work:
>
> // !!! This Q_INVOKABLE function does not work:
> void MyClass::myFunc4(int * myOutputInt1, int * myOutputInt2)
> {
>    *myOutputInt1 = 11111;
>    *myOutputInt2 = 22222;
> }
>
> one solution is to package the 2 output integers into an object of a Qt
> class that is recognizable by QML, for example, QVariant, as illustrated
> below:
>
> // This Q_INVOKABLE function appears working:
> QVariant MyClass::myFunc5()
> {
>    int myOutputInt1 = 11111;
>    int myOutputInt2 = 22222;
>
>    QScriptEngine engine;
>
>    QScriptValue value = engine.newObject();
>    value.setProperty("myOutputInt1", myOutputInt1);
>    value.setProperty("myOutputInt2", myOutputInt2);
>
>    return value.toVariant();
> }
>
> And in my QML code, I'll do something like this:
>
> var myVariant = myClassObject.myFunc5();
> var myInt1 = myVariant.myOutputInt1;
> var myInt2 = myVariant.myOutputInt2;
>
> This, although it works, does not look simple and straightforward. Is there
> a better way?
>
>
> On 10/11/2011 11:02 AM, Girish Ramakrishnan wrote:
>>
>> Hi Jonathan,
>>
>> On Tue, Oct 11, 2011 at 10:36 PM, Jonathan Zhong
>> <jonathan.zhong at panasonic.aero>  wrote:
>>>
>>> Hi,
>>>
>>> What are the valid argument types of an invokable member function of a
>>> QML extension C++ class? I have noticed that these work:
>>>
>>> Q_INVOKABLE void myFunc1(int myInputInt);
>>> Q_INVOKABLE void myFunc2(int&  myInputInt);    // but myInputInt cannot
>>> be modified.
>>>
>>> while this does not work:
>>>
>>> Q_INVOKABLE void myFunc3(int * myOutputInt);    // This will cause a
>>> runtime error when running qmlviewer.
>>>
>>> It appears that:
>>> 1. The argument can be an object of (or reference to) a basic C/C++ data
>>> type (int, int&, double, double&, ...).
>>> 2. The argument can be an object or (or reference to) a Qt class which
>>> relates to a basic QML type (QString, QString&, QVariant, QVariant&, ..).
>>> 3. The argument can be a pointer to QObject or its derived classes
>>> (QObject *, QWidget *, ...).
>>> ...
>>>
>>> Is there a Qt documentation page on this subject?
>>>
>>> Perhaps this is a related question: What are the valid return types of
>>> an invokable member function?
>>>
>> See
>> http://doc.qt.nokia.com/main-snapshot/qtbinding.html#supported-data-types
>>
>> Girish
>
>
>
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