Ability to use registered signal attributes from QML code

[White-Oak]

The original issue is White-Oak/qml-rust#8.

So the problem is :

• onPageDownloaded is a signal fn pageDownloaded(response: String)
• onPageDownloaded: console.log("Page Downloaded "+ response); fails with an error ReferenceError: response is not defined, because attributes' names are not used on registration.

I see three solutions to the original problem:

1. Use arguments:

onPageDownloaded: console.log("Page downloaded " + arguments[0]);

Remember, that in JS you can always check what are the arguments of the function (see this answer on SO)
2. Connect signal to function in qml like this

  Component.onCompleted: {
    visible = true;
    logic.pageDownloaded.connect(jsPageDownloaded);
  }

  function jsPageDownloaded(response) {
    console.log("Page downloaded " + response);
  }
  // ...

This is more verbose.
3. Provide an ability to register attribute name on registration.
Currently SignalDefinition consists of signal's name, number of attributes and their types. Is it possible to provide names of attributes as well?

[filcuc]

I would go with option 3.
Currently you can already obtain the signal argument from the qml slot.
If i'm not wrong inside a qml handler you can access the argument i-th argument with "arg0", "arg1" etc.

onNameChanged: console.log("name is", arg0)

[White-Oak]

@filcuc ah, yes, so that's the fourth option to access attributes from qml handler.
Would be awesome to be able to register signals' attributes' names!

[filcuc]

@White-Oak
What's the 4th option? Just for being more clear in what i wrote in my previous message you can access the i-th argument with "arg0" because that's what the current implementation of DOtherSide does. See https://github.com/filcuc/DOtherSide/blob/master/lib/src/DosQMetaObject.cpp#L16

Obviously this is suboptimal given that we use "arg" as prefix instead of the name that the user wrote on its signal definition (however this solution simplify the development of the binding). Give me a couple of days for adding support in C++ (probably on a separate branch).

Thank you