Re: C++ Variant type for DBus object path

[Andrejs Hanins <andrejs hanins ubnt com>]

Hi,

On 2015.04.09. 14:01, Andrejs Hanins wrote:
> Hi Kjell,
>
> On 2015.04.08. 18:08, Kjell Ahlstedt wrote:
> > A reply, at long last! I have filed bug https://bugzilla.gnome.org/show_bug.cgi?id=747508 with a patch 
> > that I think fixes your problem.
> >
> > It would be fine if you could test the patch with your quite complicated type of Variant. Can you apply 
> > and test a patch without great trouble? 
> Thanks for the patch, I'll try it later and will let you know about the results.
>
> > If not, I can send you updated versions of the glibmm/variant.h and variant.cc files.
> No need, thanks, patch is enough for me.

I have applied the patch to hg and ccg files, but it does not cause real .h and .cc files to be regenerated 
by gmmproc. I even tried to delete the source files, but still no luck. There seems to be no automatic make 
rule for regeneration (bug?). Unfortunately, I failed to understand how to regenerate the source files in 
reasonable amount of time.

Can you please help me how to regenerate the files under glib/glibmm or send regenerated variant.h/.cc files 
as you initially offered?

> > Kjell
> >
> > Den 2015-03-31 13:43, Andrejs Hanins skrev:
> > > Hi,
> > >
> > >     Currently in Glibmm GDBus it seems no straightforward way to dynamically cast VariantBase containing 
> > > some signature with object paths (o) into strictly typed Variant container. I faced the problem when 
> > > interpreting (casting) the result of standard DBus org.freedesktop.DBus.ObjectManager.GetManagedObjects() 
> > > method call which return signature is a{oa{sa{sv}}} (note 'o'). Typed Variant in my code is defined like 
> > > this:
> > >
> > >     Glib::Variant<std::map<Glib::ustring, std::map<Glib::ustring, std::map<Glib::ustring, 
> > > Glib::VariantBase>>>>
> > >
> > > but the Glib::VariantBase::cast_dynamic fails with bad_cast, because the type signature of the typed 
> > > Variant is a{sa{sa{sv}}}, thats is, object 'o' is replaced with just 's'.
> > >
> > >     My question - is there some ready-to-use type which can be used as a parameter of Variant<> template 
> > > to specify that the Variant holds an object path, not just ordinary string?
> > >
> > >     Of course, it is possible to create such a class in the client code like this (pseudo code):
> > >
> > > class obj_path_t : public Glib::ustring;
> > >
> > > template<>
> > > class Variant<obj_path_t> : public Variant<Glib::ustring>
> > > {
> > >     static const VariantType& variant_type() { return VARIANT_TYPE_OBJECT_PATH; }
> > > };
> > >
> > > so that typed Variant looks like this:
> > >
> > >     Glib::Variant<std::map<obj_path_t, std::map<Glib::ustring, std::map<Glib::ustring, 
> > > Glib::VariantBase>>>>
> > >
> > > and it actually works for me (cast_dynamic is OK), but IMO it should be provided by the Glibmm itself. 
> > > Did I overlook something? Or this is just a missing feature?
> > >
> > >
> > > BR, Andrey