[Sugar-devel] sugar-web - API for storing data

[Daniel Narvaez]

Hey,

It seems be have two (mostly) independent questions here

- How do we notify an activity of certain global events, being them
onPause/onStop or onRead/onWrite.

If we want them to be passed in activity.setup() I think we should use an
object, like {"onSomething": ..., "onSomethingElse":..}. That will allow to
subscribe only to some of the available events. With two events that would
probably be overkill but if nothing else I think onStart/onPause/onStop
should be supported, even if we also have onRead and onWrite. They are
needed for more than writing to the datastore.

Though, any reason to not use custom DOM events? This seems exactly the use
case they are designed for.
http://www.w3.org/TR/DOM-Level-3-Events/#extending_events-Custom_Events

- Should we have onRead and onWrite events.

What you are proposing is a bit different from what you have implemented.
In your patch onWrite does only a couple of things

1 Proxy both onPause and onStop to the same write method.
2 Close the activity in onStop.

I think 1 is not enough to justify onWrite existence, it's easy enough for
the concrete activity to do it if wanted.
About 2, I think the concrete activity needs more control on when it is
shut down. It might want to do so after having written some file outside
the journal, for example.

Now, you are proposing that we pass metadata in both read and write,
similarly to the gtk API. But what about the data? I don't see exactly
where you are going with this, so it would helpful if you could sketch out
that API.


That was a bit long, to summarize:

* I think onStart/onPause/onStop should be there in any case.
* On the top of those, your current onWrite implementation adds too little
to be justified.
* I tend to think we should use custom DOM events here instead of
callbacks, if possible.

On 16 August 2013 14:01, Manuel Quiñones <manuq at laptop.org> wrote:

> This is one of the most important APIs we will have, so I would
> like to open discussion on it.
>
> In GTK activities, the activity developer subclass Activity, and
> override read() and write() methods.
>
> In web activities, we don't have that kind of hierarchy.  Instead, the
> activity developer imports 'activity/activity' module, and calls
> activity.setup() .  Then she/he can use activity.getDatastoreObject()
> to read and write.
>
> In GTK activities, 'read' is called at startup and 'write' is called
> when the activity goes to the background or when it stops.  Recently,
> I added in sugar-web those notifications, with the intention to make
> web activities behave like GTK ones.
>
> I provided an initial patch and dnarvaez proposed another option:
> https://github.com/sugarlabs/sugar-web/pull/74
>
> So we can:
>
> - Let web developers connect to the 'pause' and 'stop' notifications,
>   and use the activity datastore object directly. Pro: is more
>   flexible.  Con: more work in the activity side: error handling,
>   datastore object handling.
>
> - Subscribe 'read' and 'write' functions in activity.setup() .  They
>   will be called as expected, like in GTK.  'read' will have a JSON
>   string as argument.  'write' must return a JSON string.  Pro:
>   simpler approach.  Con: less flexibility in the activity side.  A
>   mockup can be found in this comment:
>
> https://github.com/manuq/sugar-web/commit/3c2420f59c9aa8df44d2c0d639fe37b4af63f9fb#commitcomment-3872770
>
> Thoughts?  Any other ideas?
>
>
> --
> .. manuq ..
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-- 
Daniel Narvaez
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