[Interest] using a C++ class in QML in Qt6

[Stefan Seefeld]

Hi Dirk,

you may need to add one or more calls to
`QQmlApplicationEngine::addImportPath()` (
https://doc.qt.io/qt-6/qqmlengine.html#addImportPath): One to the file
system location where you installed your QML module, another to where to
find the `main.qml` file. (You may want to use Qt resources to pre-compile
`main.qml` into the binary, and then set the path accordingly).

HTH,

On Sat, Aug 31, 2024 at 5:10 PM Dirk Hohndel via Interest <
interest at qt-project.org> wrote:

> Yeah, I need one place where I can load my "main" QML file, and I need a
> way to make my C++ classes visible from within those QML files.
> So I'm not sure how I'd do that with only one "load"...
>
> In Qt5 I used the "load" to get the main.qml file and then RegisterType to
> get my C++ classes visible inside the QML code.
> In your example, how do you load your QML file?
>
> /D
>
> On Aug 31, 2024, at 14:03, ekke <ekke at ekkes-corner.org> wrote:
>
> Hi Dirk,
> in my apps ATM I'm only using one qt qml module, so I'm doing
> engine.loadFromModule(...)
> see https://t1p.de/ekkeCMakeQMLModule
>
> Have no experiences yet if you have to deal with more modules. Later will
> modularize my apps, much other refactorings must be done before ;-)
>
> but you should not do multi engine.loadFrom...
>
> good night...
>
> ekke
>
> Am 31.08.24 um 22:53 schrieb Dirk Hohndel via Interest:
>
> Hi Ekke,
>
> Thanks so much for the quick response.
>
> This is a massive project (Subsurface-mobile) that we build with CMake.
>
> Thanks for the link to your site with an explanation... this feels like
> I'm **ALMOST** there...
>
> I had already added QML_ELEMENT to the class header.
>
> In the existing code, we load the main.qml from the resource system with
>
> engine.load(QUrl(QStringLiteral("qrc:///qml/main.qml")));
>
> I added a second line
>
> engine.loadFromModule("subsurface/mobile/main", "QMLProfile");
>
> Rebuilt things and get:
>
> INFO: QQmlApplicationEngine failed to load component
> INFO: qrc:/qml/main.qml:8:1: module "subsurface.mobile.main" is not
> installed
> INFO: QQmlApplicationEngine failed to load component
> INFO: <Unknown File>: No module named "subsurface/mobile/main" found
>
> Do I need to do anything else to ensure that the type is visible and
> subsequently the module is found?
>
> Thanks again for your help!
>
> /D
>
> On Aug 31, 2024, at 12:56, ekke <ekke at ekkes-corner.org>
> <ekke at ekkes-corner.org> wrote:
>
> What is your build system ? QMake or CMake ?
>
> Instead of qmlRegisterType you should use QML_ELEMENT
> see https://t1p.de/ekkeQML_ELEMENT
>
> ekke
>
> Am 31.08.24 um 21:23 schrieb Dirk Hohndel via Interest:
>
>
> Hi there,
>
> I've been trying to figure out how to port a QML app from Qt5 to Qt6 and
> have been unable to solve what seems like a fairly basic issue.
>
> In the Qt5 version, I was able to make a class available from C++ by
> simply calling
>
> ...
> qmlRegisterType<QMLProfile>("org.subsurfacedivelog.mobile", 1, 0,
> "QMLProfile)
> ...
>
> in the C++ code and then using
>
> import org.subsurfacedivelog.mobile
>
> in the QML file in order to then be able to use that type as
>
> QMLProfile {
> ...
> }
>
> in the QML code.
>
> When I try this code unmodified, it compiles fine, but at run time tells
> me that it cannot find the org.subsurfacedivelog.mobile module when it
> encounters that import org.subsurfacedivelog.mobile line.
>
> So I tried some searching and found several pages in the Qt6 documentation
> that all seem to imply that this isn't how things should be done in Qt6 and
> that instead I would need to go down the route of defining a separate QML
> module with its own compile unit (is this true? why would you disable this
> core feature???)
>
> And then trying to do that, I fail to get the module to compile with
> missing include paths.
> If it turns out that that's the only way to go, I'll happily give a lot
> more details on this issue -- but I'd love to first get back to the
> previous approach.
> Is there still a way in Qt6 to register a Type with QML without having to
> create separate modules?
>
> Thanks
>
> /D
>
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-- 

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