Jquery UI autocomplete - using value from a previous select field

I want to autocomple开发者_如何学JAVAte a Cities text input, but only search for cities in the country that was previously selected. The code I have seems like it should work, but it's not sending the correct country value.

The form:

Country: <select name='country' id='country'>
             <option value='US'>USA</option>
             <option value='UK'>United Kingdom</option>
         </select><br/>
City: <input type='text' name='city' id='city' />

The js:

$( "#city" ).autocomplete({
            source: "searchCities/" + $('select#country option:selected').val(),
            minLength: 2
        });

The URL structure should be 'searchCities/UK?term=foo' and the SQL statement is searching for the value of 'term' where the country code is 'UK'. If I type in the URL manually, it works without a problem (limiting to only the country)... and the autocomplete works in the form. However, it returns ALL cities without limiting by the country code.

Is there something I may be missing? Or maybe a better way to accomplish this? Thanks!

---

If you are not doing so already - you should modify the autocomplete's source attribute each time the select box's selected value is changed.

you can destroy and re-build the autocomplete every time the user selects a new value into the select box:

<script>
   function renewAutocomplete() {
      $( "#city" ).autocomplete("destroy");
      $( "#city" ).autocomplete({
            source: "searchCities/" + $('select#country option:selected').val(),
            minLength: 2
        });
   }
</script>
Country:
<select name='country' id='country' onchange='renewAutocomplete();'>
   <option value='US'>USA</option>
   <option value='UK'>United Kingdom</option>
</select>
<br/>
City: <input type='text' name='city' id='city' />

or maybe it is better not to destroy it and re-build it, rather modify its source attribute:

<script>
   function renewAutocomplete() {
      $( "#city" ).autocomplete("option", "source", "searchCities/" + $('select#country option:selected').val());
   }
</script>

---

Try this one

    $("#city").unautocomplete().autocomplete(

              base_url+"index.php/index/autocompletecities/", 

              {

               extraParams:                 
                   {country:$('#country').val()} 

});