ObjectManager not used for children objects?

[Jan Grulich]

On 11/12/2013 07:00 PM, Dan Williams wrote:
>> Hi,
>> 
>> Jan Grulich was working on MM Qt bindings and found that the
>> ObjectManager doesn't know about all the objects that MM exports.  The
>> objects are getting exported with g_dbus_interface_skeleton_export(),
>> but should they be exported with g_dbus_object_manager_server_export()
>> instead?  Watching with dbus-monitor, I'm not seeing any ObjectManager
>> interface signals when new Bearers get created, for example.
>> 
>> Exporting with g_dbus_object_manager_server_export() would require
>> either pushing the ObjectManager instance down into a couple classes
>> (Bearer, SIM, SMS), but maybe that's the right thing to do instead of a
>> singleton with a global get() function?
>> 

>For now, the ObjectManager interface is only applicable to the 'manager'
>object, and only notifies about added/removed modem objects or modem
>interfaces. It does not apply to SIM, Bearer or SMS objects, but we have
>other ways to get notified about those:
> * SIM: "Sim" property in the "Modem" interface. Clients wanting to get
>notified when the SIM object is available can watch for changes in that
>property.
> * SMS: "List" method in the "Messaging" interface, which lists all
>currently available SMS objects; plus "Added" signal to notify about new
>ones.
> * Bearer: "ListBearers" in the "Modem" interface, to list which are
>available.

For SIM cards and SMS it is probably okay, but not for Bearers, because ListBearers method is useless for us. You don't know when a new Bearer appears and you would have to call this method in some interval to always know about new Bearers. It would be better to have a property instead of this method and notify about new Bearers in PropertiesChanged signal, like it is probably everywhere in NetworkManager.

>>From one point of view, we could get the manager notify about those as
>well, but then these 'sub' objects wouldn't be seen as being managed by
>specific modems. You would get object-added for a SIM, for example, but
>you still would need to look at all available modems to see to which
>modem object it applies.

>Another option would have been to let each Modem object implement the
>ObjectManager interface itself, but then it would be managing objects of
>very different types, which I'm not sure it looks very good. For
>example, if you wanted to look for which SIM object applies to a given
>Modem, you would be listing also all SMS and bearer objects before being
>able to know which path the SIM object has.

Regards,
Jan

-- 
Jan Grulich 
Red Hat Czech, s.r.o
jgrulich at redhat.com