Hi Olivier
With your help it was easy to make some code that python liked:
def node_clicked(self, widget, item):
def play_uri(self=dfr_self, station=dfr_station):
player =
self.frontend.retrieve_controllers('/poblesec/music_player')[0]
player.player.play_model(station)
main = self.frontend.retrieve_controllers('/poblesec')[0]
main.show_music_player()
self.stop_loading_animation()
dfr = defer.Deferred().addCallback(play_uri, self, item)
return dfr
But the play is not called (and you stated there is no magic :-)
But when looking into the shoutcast play-method that is called implicit using
some sort of Elisa command pattern I see the following:
def play_station(self, station):
resource, dfr = application.resource_manager.get(station.get_playable,
station)
def play(station):
player =
self.frontend.retrieve_controllers('/poblesec/music_player')[0]
player.player.play_model(station)
main = self.frontend.retrieve_controllers('/poblesec')[0]
main.show_music_player()
self.stop_loading_animation()
dfr.addCallback(play)
As seen a deferred comes "magically" (:-) in hand and the method "play" is
added.
I would like to do the same but have no resource in the resource manager (I
think??)
Please Advice!
Best Regards,
Kristian
> Date: Wed, 4 Feb 2009 09:50:22 +0100
> From: [email protected]
> To: [email protected]
> CC: [email protected]
> Subject: Re: [Elisa] Problems with deferred and Elisa
>
> Hi Kristian,
>
> Kristian Lippert a écrit :
> > Hi
> > I have a play-method in my own stream-player and it works:
> >
> > def node_clicked(self, widget, item):
> > def play_uri(self, station):
> > # We already know the real URL of the playable audio stream, no
> > # need to query the resource manager
> > # get player and start playing
> > player =
> > self.frontend.retrieve_controllers('/poblesec/music_player')[0]
> > player.player.play_model(station)
> > main = self.frontend.retrieve_controllers('/poblesec')[0]
> > main.show_music_player()
> > self.stop_loading_animation()
> >
> > pdb.set_trace()
> > if isinstance(item, Action):
> > item.run()
>
> Side note: this test is useless if you know that your list contains only
> PlayableModels.
>
> > elif isinstance(item, PlayableModel):
> > play_uri(self, item)
> >
> > It works fine but if there are problems with the stream it will hang for
> > a while, so I thought I could use a deferred, like:
> >
> > def node_clicked(self, widget, item):
> >
> > def play_uri(self, station):
> > # We already know the real URL of the playable audio stream, no
> > # need to query the resource manager
> > # get player and start playing
> > player =
> > self.frontend.retrieve_controllers('/poblesec/music_player')[0]
> > player.player.play_model(station)
> >
> > main = self.frontend.retrieve_controllers('/poblesec')[0]
> > main.show_music_player()
> > self.stop_loading_animation()
> >
> > pdb.set_trace()
> > if isinstance(item, Action):
> > item.run()
> > elif isinstance(item, PlayableModel):
> > dfr = defer.Deferred().addCallback(play_uri)
> > return dfr(self, item)
> >
> > My problem is that I am not sure:
> > 1) Do I create the deferred in the right manner?
>
> Not really, see my explanation below.
>
> > 2) How does the binding of the parameters happen?
>
> Simply pass extra arguments to the addCallback method, they are going to
> be passed to the callback after the result argument.
>
> > 3) Do I need to activate the deferred my self or will this happen by
> > magic by it self?
>
> If you instantiate a deferred with defer.Deferred(), then nothing won't
> happen until someone/something invokes its callback() method, that will
> in turn trigger the chained callbacks to be called.
>
> One simple example:
>
> def cb(result, arg1, arg2):
> print result, arg1, arg2
>
> dfr = defer.Deferred()
> dfr.addCallback(cb, 'hello', 'world')
> dfr.callback()
>
> If you want to try it out as is in a python shell, you'll have to import
> twisted.internet.reactor, and call reactor.run().
>
> > As far as I can read the deferred can be compared to the .NET
> > asynchronous delegates or boost::thread. Boost::thread is much simpler
> > but they share the problem regarding binding variables.
>
> Unfortunately deferreds won't magically make synchronous code
> asynchronous. They are a tool to help you write asynchronous code, but
> in that case the underlying methods you are calling
> (player.player.play_model, main.show_music_player,
> self.stop_loading_animation) are all synchronous (in the sense that they
> don't return a deferred). You could mock asynchrony by calling them in a
> thread, but that's highly discouraged so I'm not giving you the link to
> the doc of the method that allows that ;)
>
> > Please help me fix the code!
> >
> > Best Regards,
> > Kristian
>
> I hope this helps.
>
> Olivier
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