[Interest] Better Q_PROPERTY() ?

Pierre-Yves Siret py.siret at gmail.com
Fri Dec 7 13:00:37 CET 2018

> Hi all,
> I have found a little project which I found very nice to use especially if
> you want expose you C++ class to QML.
> Take a look at this project developed by Thomas Boutroue
> http://gitlab.unique-conception.org/qt-qml-tricks/qt-supermacros
> and
> http://gitlab.unique-conception.org/qt-qml-tricks/qt-qml-models
> Here is the link to the Lightning Talk he had at QtWS15 in Berlin.
> https://www.youtube.com/watch?v=96XAaH97XYo
> I use this tools in my Qt/QML application, and it saves me so much time!
> Regards
> Fabrice

I've used those and personnal macros before but I've since stopped from
doing it.

At first it's useful but then you need for example a property that's
computed from another one, or some special case properties.
Should I create a specific macro for this case used once or twice in the
project, or should I use a normal Q_PROPERTY and have a weird mix of non-Qt
macros and Q_PROPERTY, making your code less readable?
Sometimes l also want to set a breakpoint in a getter or setter, macros
don't help for that.

> Q_PROPERTY_RWN(proptype, arg)  -->  Q_PROPERTY(proptype  arg READ arg
WRITE setArg NOTIFY argChanged)
Qt Creator makes it easy to write Q_PROPERTY with its snippets.
You can type Q_PROPERTY <ctrl-space> type <tab> name <return> and it will
generate Q_PROPERTY(type  name READ name WRITE setName NOTIFY nameChanged)
You can add your own custom snippets if you want constant or non writable

The only gripe I have with Qt Creator regarding properties is its
Q_PROPERTY refactoring.
* It adds setters as slots (
https://bugreports.qt.io/browse/QTCREATORBUG-15779 )
* Non scalar types like QString are passed as value to the property setter
( whereas if you create a QString member variable and you do Refactor /
Create Setter Member Function, the QString is passed as a const ref)
* Notify signals have parameters

That means that when I refactor a Q_PROPERTY to add missing members, I have
to do a second manual pass where I :
1 - Remove the signal parameter in the signal declaration and remove it in
the setter definition
2 - Move the setter from the public slots to under the getter
3 - Refactor move their definition to the .cpp
4 - Remove the useless added new lines.

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