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wait for callback and use results of return value

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Sabine Manaa

wait for callback and use results of return value

Hi,

I have spent several hours in the following problem: I want to use a list of
names in Pharo which I get from amazon S3. But it is not a aws problem but a
problem of understanding how to use callbacks/asynchronus code and return
values. This is a simplified version for describing the problem. Pressing
the button "testing" evaluates the Javascript code below. The result, I want
to use in Pharo is the result which is at *1*. But the method immediately
returns the result at *2*, because it dose not wait for the function to be
completed. This is more a javascript question but perhaps someone had a
similar problem.
Perhaps someone has an idea. I already tried with promises but did not
succeed.

Sabine

renderTestOn: html
html
html:
''.

html div
onClick:
(html jQuery ajax callback: [ :var | var inspect ] value: (JSStream on:
'getS3Data()'));
with: 'testing'

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Karsten Kusche

Re: wait for callback and use results of return value

Hi Sabine,

i don’t know what exactly you mean with 1 and 2 but i assume getS3Data() returns immediately and its result is sent to the server. If getS3Data() performs an asynchronous call, the method is pretty quick and doesn’t block.

What you need to do is something like this (from the jQuery website):

var jqxhr = $.ajax( "example.php" )
  .done(function() {
    alert( "success" );
  })
  .fail(function() {
    alert( "error" );
  })
  .always(function() {
    alert( "complete" );
  });

You create the Ajax request to S3 and in the done-function you can to handle the result and pass it to a callback. I can’t tell you how to do that out of my head though, it shouldn’t be too hard though.

Kind Regards

Karsten

Am 21. November 2018 um 14:57:04, Sabine Manaa ([hidden email]) schrieb:

Hi,

I have spent several hours in the following problem: I want to use a list of
names in Pharo which I get from amazon S3. But it is not a aws problem but a
problem of understanding how to use callbacks/asynchronus code and return
values. This is a simplified version for describing the problem. Pressing
the button "testing" evaluates the Javascript code below. The result, I want
to use in Pharo is the result which is at *1*. But the method immediately
returns the result at *2*, because it dose not wait for the function to be
completed. This is more a javascript question but perhaps someone had a
similar problem.
Perhaps someone has an idea. I already tried with promises but did not
succeed.

Sabine

renderTestOn: html
html
html:
''.

html div
onClick:
(html jQuery ajax callback: [ :var | var inspect ] value: (JSStream on:
'getS3Data()'));
with: 'testing'

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Johan Brichau-2

Re: wait for callback and use results of return value

In reply to this post by Sabine Manaa

Hi Sabine,

I assume you need to pass a callback function as argument to `getS3Data` that will be called when the result data is ready?

The following wraps the Ajax call in a function with one argument and passes it as an argument to `getS3Data’.
Invoking the function with a value invokes the ajax request with the given value.

html javascript
call: 'getS3Data'
with:
((html jQuery ajax
callback: [ :var | var inspect ]
value: (html javascript alias: 'value')) asFunction: #(value))

Does this come close?
cheers
Johan

> On 21 Nov 2018, at 14:56, Sabine Manaa <[hidden email]> wrote:
>
> Hi,
>
> I have spent several hours in the following problem: I want to use a list of
> names in Pharo which I get from amazon S3. But it is not a aws problem but a
> problem of understanding how to use callbacks/asynchronus code and return
> values. This is a simplified version for describing the problem. Pressing
> the button "testing" evaluates the Javascript code below. The result, I want
> to use in Pharo is the result which is at *1*. But the method immediately
> returns the result at *2*, because it dose not wait for the function to be
> completed. This is more a javascript question but perhaps someone had a
> similar problem.
> Perhaps someone has an idea. I already tried with promises but did not
> succeed.
>
> Sabine
>
>
> renderTestOn: html
> html
> html:
> ''.
>
> html div
> onClick:
> (html jQuery ajax callback: [ :var | var inspect ] value: (JSStream on:
> 'getS3Data()'));
> with: 'testing'
>
>
>
> --
> Sent from: http://forum.world.st/Seaside-General-f86180.html
> _______________________________________________
> seaside mailing list
> [hidden email]
> http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/seaside

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Sabine Manaa

Re: wait for callback and use results of return value

Yesterday I was asking this question and also asked in discord.
In discord I wrote today with Johan Brichau.
He gave the solution to me and I want to share it here because when I have a
problem, I often look here.
The solution was like this (I remove the script brackets for the mailing
list).

Thanks a lot, Johan!

The task is to call a javascript method and return a result from somewhere
in the javascript.
Clicking on the button opens an inspector in the smalltalk image.

renderTestOn: html
html
html:
'script
function getS3Data(callback) {
callback(''this goes back to the smalltalk image'' );
}
/script
'.
html button
onClick:
((html javascript alias: 'getS3Data')
apply:
{((html jQuery ajax callback: [ :var | var inspect ] value: (html
javascript alias: 'value')) asFunction: #(value))});
with: 'tedt'

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