maybe types - was: the GetAll method and invalid properties

Mike Gorse mgorse at
Wed Apr 11 13:02:11 PDT 2012

On Tue, 10 Apr 2012, Simon McVittie wrote:

> There is a proposal[1] to add 'm' (maybe) types, which are like 'a'
> (array) types but can only have 0 or 1 elements in the array: so you
> either have an object path (or whatever the element's type is), or
> "nothing". These are not yet supported, though, and nobody's actively
> working on them, so they're unlikely to be in D-Bus 1.6 at this stage.
> [1]

Fwiw, I just took a look at the bug, to try to figure out what would need 
to be done (AT-SPI does something similar where some methods might return 
an object, or they might return null, and currently there is a special 
object path used to indicate a null object, so in theory this could be 
done with a maybe type, at least in the long term). Anyway, there are some 
patches on the bug along with comments from various people who reviewed 
the patches. Then the patches were updated by the person who originally 
wrote them, so they could use a review from someone.


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