On 3/20/2020 12:53 AM, Jason H wrote:
That's only part of it. I want Qt to support it too, mainly for
> console-qDebug output, but all for use in UI. (Imagine a text element
> that displays a socket state as it's text.)
I understand, my reply wasn't aimed at your original question.
FWIW, the basic issue seems to be that enums are treated as simple
integers in QML (the QMetaType on the C++ side is always
QMetaType::Int). Otherwise it would be easy to just
QVariant::toString() them and see the value name like in C++. I couldn't
come up with any clever way to provide a generic C++ toString() method
for enum values sent from QML. The actual type info is "lost in
translation" so to speak.
Of course you could make a toString() helper method for each actual enum
type (eg. myEnumToString()) and invoke that from QML (from a gadget
singleton or a context property object, or whatever). Which could then
use QMetaEnum to deliver the actual name. Seems like quite a bit of
overhead for something like that, but then again if you have a lot of
values or they change often, it might be preferable to a value<->name
lookup table in QML/JS.
OTOH if we're talking purely in QML/JS then you could just use an object
to store the values and names together. There's a big thread on it at
StackOverflow[1]. Here's one way which is only a little ugly because the
Qt ES version doesn't seem to support Symbol().description [2] (yet?):
const Positions = Object.freeze({
Unspecified: Symbol(1),
BackFace: Symbol(2),
FrontFace: Symbol(4)
});
const face = Positions.FrontFace;
console.log(face, String(face).slice(7, -1)); // Sumbol(4), 4
switch (face) {
case Positions.BackFace:
console.log("The back");
break;
case Positions.FrontFace:
console.log("The front");
break;
default:
console.log("Unknown face");
}
Obviously one could come up with a little helper function/object which
makes this prettier. And you could make it auto-assign incremental
values if one isn't provided in the "constructor" (like a C enum does)
Cheers,
-Max
[1]:
https://stackoverflow.com/questions/287903/what-is-the-preferred-syntax-for-defining-enums-in-javascript
[2]:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/description
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