How to extend QObject to implement signals and slots

[therecipe]

How to extend QObject to implement signals and slots

[therecipe]

Hey

Unfortunately, it's currently not possible to add your own signals or slots to existing classes.
The binding currently just allows you to use/override the existing signals or virtual functions.

The problem is, that if you would want to add new signals/slots to your own subclass, you would need to manually create the *.cpp, *.h and the *.go file and also run the http://doc.qt.io/qt-5/moc.html tool.

This could be automated (probably integrated into qtdeploy), with a function that parses the *.go files from your project and creates the missing files on the fly. But I haven't really looked into that yet.

However, if you just want to be able to call Go functions from Qml or Qml functions from Go, there is a dirty workaround :)

I added a new example, which demonstrates how you can do it. https://github.com/therecipe/qt/tree/master/internal/examples/quick/bridge (this example currently doesn't work on android because of the use of QQuickWidget, but it works with qt 5.6)

Calling Go functions from Qml, works by using a QWidget as a proxy to receive Json encoded messages from Qml.

Calling Qml functions from Go, works by setting a "onPropertyChanged" method to receive Json encoded messages from Go. (the QMetaObject::invokeMethod, is currently not usable)

If you got any questions or run into problems, feel free to ask.

[longlongh4]

Hi
I have tried both, the second way seems confused when project grows larger. So I think the first way is better (even though we must make our hand dirty with C++, but who cares ^_^ ), I have sent a pull request to add an example about how to mix QObject signals&slots with golang .

How about implement a go generator to auto implement bridge c++ class to do this, like code below:

//go:generate goQt blahblah...
type SignalHandler interface {
    ReceiveValueFromQml(value string) `qSignal`
    SendValueToQml(value string) `qSlot`
}

[therecipe]

Hey

Thanks for the pull request :)
I started working on a way to auto implement new signals and slots.
The qtdeploy tool will now execute a new tool called qtmoc, which parses the local files and creates the needed files on the fly.

The syntax will look like this:

//go:generate qtmoc
type SignalHandler struct {
    core.QObject

    _ func(value string) `signal:sendToQml`
    _ func(value string) `slot:callbackFromQml`
}

You will also be able to subclass these classes, so something like this will work also:

//go:generate qtmoc
type TopSignalHandler struct {
    SignalHandler

    _ func(value string) `signal:sendToQml2`
    _ func(value string) `slot:callbackFromQml2`
}

[therecipe]

Okay, I pushed the changes.

You can now execute qtmoc to generate the needed files.
I also updated the example quick/bridge and quick/bridge2.

[longlongh4]

That's great, thank you!