On 19/06/16 02:27, Carsten Haitzler wrote:
> On Fri, 17 Jun 2016 09:41:39 +0100 Tom Hacohen <t...@osg.samsung.com> said:
>
>> On 17/06/16 03:28, Carsten Haitzler wrote:
>>> On Thu, 16 Jun 2016 19:13:20 +0100 Tom Hacohen <t...@osg.samsung.com> said:
>>>
>>>> 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.
>>>
>>> just for convenience i think having a special eo_promise_then(obj, cb1, cb2,
>>> data); may be best as its the simplest and is not pretending to ADD a cb in
>>> the name. it sets it explicitly. this needs special treatment like the eo
>>> event callbacks of course.
>>>
>>> but using an eo event is possible by override indeed, but here is the issue.
>>> you have to wait until either "then" or "else" or both are set. since you
>>> set one then set another... you will have to always add one of them as a
>>> NULL or dummy cb just to do this. having a single method/func set both
>>> makes more sense. in fact this likely needs manual binding/.handling per
>>> language anyway. i'm really only thinking of eo events for EXTRA features
>>> like progress events on a promise that happen before the success/fail cb's
>>> above.
>>>
>>>
>>
>> This is explained better in my reply to the initial post of this thread,
>> but essentially you don't. What you are missing, and why life-cycle can
>> be pretty broken, and why this doesn't matter is that you can register a
>> few "then" and a few "cancel" in promises. That is actually the power of
>> promises, that you can chain them and use them for a few things. This is
>> dealt with nicely. See the post I mentioned.
>
> register a few then/else cb's on the same promise? at least that should not be
> possible (it should not work). on;y one else/then cb (zero or one of each).
>
>

Why not? Anyhow, as I said, that is very common in js land and how race 
and all are probably implemented.

--
Tom.

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