.result is not a function error

.result is not a function error

Hello,
I'm trying to implement jQuery UI autocompleter with Symfony and I keep getting this error: 

Uncaught TypeError: Object #<an Object> has no method 'result'
(Google Chrome)

Firefox error console shows "result is not a function" which I guess means exactly the same.

Here is code autogenerated by Symfony which causes the error:

<script type="text/javascript">
jQuery(document).ready(function() {
jQuery("#field_id")
.autocomplete('/frontend_dev.php/module/ajax', jQuery.extend({}, {
dataType: 'json',
parse: function(data) {
var parsed = [];
for (key in data) {
parsed[parsed.length] = { data: [ data[key], key ], value: data[key], result: data[key] };
}
return parsed;
}
}, { }))
.result(function(event, data) { jQuery("#field_id").val(data[1]); });
});
</script>

I'm using 1.8rc3 version. 

Thanks in advance for your help!