Retrieve variable set within getJSON callback function

Question

I am forced to use data from within the getJSON callback function outside of that function. Have a look:

$('#stars').raty({
        score: function() {
            var $value = 0;
            var $id = <?=$id?>;
            $.getJSON("getuserrating.php?id=" + $id, function(data) {
                $.each(data, function(key, val) {
                    $value = val;
                });
            });
            return $value;
        },
    });

This is what I tried but it failed, the $value is still set to 0, although inside the callback it's definitely set to an actual value. I know why it fails, because the AJAX request is send asynchronously. The problem is, the correct way, doing everything inside the callback, is not possible. As you can see I need to retrieve the JSON object within the raty (a plugin) setup. I would just use $.ajax() and set that to synchronous but the documentation marks this as deprecated for 1.8. I'd rather not introduce a solution that I know will be deprecated in the future.

Is there any way at all to do this? Maybe I just don't see the forest for the trees and there's an easy solution right before me. Thanks in advance :)

This question has been already asked millions of times. Please use the corresponding search engines to find the duplicate questions. But to simplify your efforts, no, there's no way to achieve that other than using the async: false switch which obviously is not something that I would recommend you doing. Just get accustomed to asynchronous programming and throw into the trash libraries and plugins that do not support this paradigm and replace them with libraries that do support it and provide you the possibility to work with callbacks. — Darin Dimitrov
– Darin Dimitrov, Commented Jun 19, 2012 at 18:40
Nope, there is not. Have a look at the documentation if the plugin and see whether it provides a way to use asynchronous functions as values. If not, there is nothing you can do, despite suggesting this to the developer. — Felix Kling
– Felix Kling, Commented Jun 19, 2012 at 18:40
@DarinDimitrov I specifically mentioned that I know what's causing the problem but that I'm looking for a workaround other than async: false. The "millions" of questions you refer to were all solved by making the OP work within the callback. As you might have noticed, my problem was that I didn't see a way to solve my matter within the callback itself. Hence, those millions of answers did not actually answer my specific question. Suggesting to trash a widely spread plugin that does its main job best does not seem very supportive either. — janb
– janb, Commented Jun 19, 2012 at 21:52

charlietfl · Accepted Answer · 2012-06-19 19:05:10Z

4

Approach is backwards if you need to use ajax to get the score.

Make the ajax call first, then pass the value to score within the ajax success

$.getJSON("getuserrating.php?id=" + $id, function(data) {
          /* pseudo code here since I don't know the plugin and it's data requirments*/
         var score= data.score;
         $('#stars').raty({
             score: score
         });      
});

EDIT: you can still pass the data into a score function this way also

edited Jun 19, 2012 at 19:05

answered Jun 19, 2012 at 18:49

charlietfl

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4 Comments

Felix Kling Over a year ago

I thought the same, as long as a primitive value for score is acceptable.

janb Over a year ago

Thanks a lot for the input. This looked very promising and exactly like a solution that I had stupidly overlooked but I'm running into problems. When trying to call the raty function within the callback "$('#stars').raty is not a function" errors are triggered. This seems to suggest the raty plugin has not been loaded yet, but that doesn't make a lot of sense. Any ideas?

charlietfl Over a year ago

are you loading jquery more than once in page, if so, any plugins attached to first load get wiped out. Also make sure options passed to plugin are valid code

janb Over a year ago

thanks :) I'm still researching where exactly it happens but you are right, the plugin gets wiped. Your solution works fine in a minimal test environment.

Floydian · Accepted Answer · 2012-06-19 18:45:47Z

0

Maybe this (taken from jquery getJSON api doc http://api.jquery.com/jQuery.getJSON/) could work:

// Assign handlers immediately after making the request,
// and remember the jqxhr object for this request
var jqxhr = $.getJSON("example.json", function() {
  alert("success");
})
.success(function() { alert("second success"); })
.error(function() { alert("error"); })
.complete(function() { alert("complete"); });

// perform other work here ...

// Set another completion function for the request above
jqxhr.complete(function(){ alert("second complete"); });

Just assign another raty attribute instead of returning.

answered Jun 19, 2012 at 18:45

Floydian

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1 Comment

user400654 Over a year ago

.success .error and .complete are depreciated and replaced by .done .fail and .always, the documentation seems to be out of date on that page. api.jquery.com/jQuery.ajax

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