Watching for registration with python

[Colin Helliwell]

> On 01 September 2017 at 17:17 Dan Williams <dcbw at redhat.com> wrote:
> 
> On Fri, 2017-09-01 at 10:51 -0500, Dan Williams wrote:
> 
> > On Fri, 2017-09-01 at 14:26 +0100, colin.helliwell at ln-systems.com
> > wrote:
> > 
> > > I've been having a look at the modem-watcher-python example, and
> > > would like
> > > to do something similar - namely wait until the modem has
> > > registered
> > > on the
> > > network and then grab the MCC/MNC.
> > > Is there some sort of event I can hook for this (similar to what
> > > the
> > > example
> > > does with ' object-added'), or do I just need to poll?
> > > Thanks
> > 
> > ModemWatcher.py has the modem watching stuff already. What you want
> > to
> > do is modify the on_object_added() method to:
> > 
> > 1) check modem.get_state() >= ModemManager.ModemState.REGISTERED
> > 2) if yes, then grab the MCC/MNC with something like:
> > 
> > mccmnc = obj.get_modem_3gpp().get_operator_code()
> > 
> > 3) if no, then connect to the 'state' property notifier:
> > 
> > modem.connect('notify::state', self.modem_state_changed, obj)
> > 
> > and then have a separate function that handles that change:
> > 
> > def modem_state_changed(self, modem, prop, obj):
> >  if modem.get_state() >= ModemManager.ModemState.REGISTERED:
> >  mccmnc = obj.get_modem_3gpp().get_operator_code()
> > 
...
> 

Thanks for the pointers, Dan. But isn't there a risk of race hazard (the state change) in between #1 and #3?
In which case I was thinking (bearing in mind it's dinner time on a Friday...):
Connect to the 'state' property notifier *straight away* in the on_object_added() method; *then* also check modem.get_state() in there too.  [Provided I'm ok with the resultant code being potentially called twice]