Software evolution according to applications of “maybe” containers (nullable data types)

I became curious again to improve the software situation another bit around the usage of “maybe” containers.

:thinking: Would you like to add any information to related feature requests?

See also further information sources:

  • Description for the GVariant type system
  • Constructing an empty maybe GVariant object based on a previous GVariant object
  • Support for “maybe” containers (nullable data types)

The feature request that Markus is talking about is this one:


I’m quite sure that would be useful somewhere in Dconf Editor, as it’s a place where GVariant are used and abused in every way possible. But that should not exactly count as a proof the method would be useful in everyday cases.

But that should not exactly count as a proof the method would be useful in everyday cases.

Such a view is fine.

I imagine that empty GVariant maybe objects will occasionally be needed in data models.

In general I see the benefits of “maybe” types but in GVariant it’s kinda nasty given they are incompatible with dbus

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Do software development challenges need further clarification according to D-Bus applications?

Honestly no idea what your saying here

Potentially - You could use the wrap-in-array trick but that’s adding slightly magic behaviour and other dbus clients won’t desugar it (in fact I’m not sure gio could safely either?)

Off-topic really

Yes I’m well aware of NULL :grinning_face_with_smiling_eyes:

How does such a view fit to the type code “109 (ASCII ‘m’)” in the summary of D-Bus types?

Category Conventional Name Code Description
reserved (reserved) 109 (ASCII ‘m’) Reserved for a ‘maybe’ type compatible with the one in GVariant, and must not appear in signatures used on D-Bus until specified here

So the definition is “nothing at all, but maybe one day do whatever GLib does - until then it’s invalid”

Thus whatever GVariant does, even if incompatible with previous versions GLib releases, is fully compliant with the spec

Are any solution approaches still waiting for the final acceptance?

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