On Thu, Jun 16, 2016 at 11:13 AM, Tom Hacohen <[email protected]> wrote:
> On 03/06/16 20:17, Cedric BAIL wrote:
> <snip>
>>>> also promises should become eo objects with event cb's
>>>> so they work just like everything else. i can ref, unref, delete and 
>>>> whatever
>>>> them like everything else.
>>
>> As said above, this does work. Example with event :
>> eo_promise = efl_file_set(image, "toto.jpg", NULL);
>> eo_event_callback_array_add(eo_promise, promise_callbacks1(), NULL);
>> eo_event_callback_array_add(eo_promise, promise_callbacks2(), NULL);
>>
>> In this 3 lines, there is already 2 case in which that fail. First if,
>> the object is done before the callback is set, data are lost and there
>> is no way to get any event. Ofcourse, we can override the behavior of
>> events on this eo_promise completely. Now let's imagine, that we
>> actually do always store the events, so that everytime someone
>> register a callback we can send the event. Still you can't auto del
>> the object at any point in time, you have to force the user to
>> implement the eo_del and to always provide both a then and cancel
>> callback.
>>
>> Other possibility, it is an event on the object itself.
>> eo_event_callback_array_add(image, promise_callbacks1(), NULL);
>> efl_file_set(image, "toto.jpg", NULL);
>> eo_event_callback_array_add(image, promise_callbacks2(), NULL);
>>
>> Same again, this can not work. The first group of event handler,
>> promise_callbacks1(), may actually be triggered by a previously
>> running promise on the object, so you have to first forcefully stop
>> the previous operation. This would add complexity. And still the
>> second callback has the same issue as the previous case, if it is a
>> normal eo event, it could have been triggered before any callback get
>> registered and the event be lost... Same story short, doesn't work.
>>
>
> I'm currently reading through the thread, and I didn't see anything
> mentioned about this other than a casual remark you made, so just wanted
> to make it crystal clear regarding implementing it as an Eo object.
> The whole point/magic of inheritance is that you can and are supposed to
> override functions if needed. Overriding callback add to call the
> callback immediately upon addition (if already done) is how I would
> implement promise callbacks. It's clean, easy and as intended. This is
> definitely not a problem.

I hope that by the end of this thread you do understand why this
doesn't work. Basically the point is that you don't have to eo_del a
promise ever. Once you set the callback on it and when all the
expected callback are called, the promise vanish. Inheritance on
callback, that is a given, thanks. Now, how do you make sure you have
all the callback registered and that you have delivered the value to
everyone that expect it before the promise commit succide ?
-- 
Cedric BAIL

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