当表单验证失败时，无法在 codeIgniter 中接收 ajax 数据

这是我在codeIgniter中的第一个项目。在这里，我尝试使用验证器控制器类的 form_submit（） 方法验证表单......我使用 jquery 的 ajax 方法通过调用验证器控制器的 get_cities（） 方法和 get_sub_category （） 方法在我的表单中生成两个下拉字段。值得一提的是，我正在使用一个外部下拉列表.js文件，该文件已与我的表单视图链接。这是下拉列表.js文件

$(document).ready(function () {
$('#city_h').hide();
$('#sub_category_h').hide();   
//function to dynamically populate CITY according to STATE
$('#state').change(function () {
    var state_id = $('#state').val();
    var state_id = state_id.trim();
    if (state_id/* != ""*/) {
        //Need to handle form submission more efficiently
        /**
         * For the time being, i am checking if the user has submitted the form  or not
         * By the following if else block but in future i will try to handle it from CONTROLLER
         */
        if ($(location).attr('href') == "http://localhost/ci_practice/") {
            var post_url = "index.php/validator/get_cities/" + state_id;
        } else {
            var post_url = "get_cities/" + state_id;
        }
        //Need to handle form submission more efficiently
        $.ajax({
            type: "POST",
            url: post_url,
            success: function (cities) //we're calling the response json array 'cities'
            {
                $('#city').empty();
                $('#city_h').show();
                $.each(cities, function (ci_id, ci_name)
                {
                    var opt = $('<option />'); // here we're creating a new select option for each group
                    opt.val(ci_id);
                    opt.text(ci_name);
                    $('#city').append(opt);
                });
            } //end success
        }); //end AJAX
    } else {
        $('#city').empty();
        $('#city_h').hide();
    }//end if
}); //end change
//function to dynamically populate SUBCATEGORY according to CATEGORY
$('#category').change(function () {
    var category_id = $('#category').val();
    var category_id = category_id.trim();
    if (category_id/* != ""*/) {
        //Need to handle form submission more efficiently
        /**
         * For the time being, i am checking if the user has submitted the form  or not
         * By the following if else block but in future i will try to handle it from CONTROLLER
         */
        if ($(location).attr('href') == "http://localhost/ci_practice/") {
            var post_url = "index.php/validator/get_sub_category/" + category_id;
        } else {
            var post_url = "get_sub_category/" + category_id;
        }
        //Need to handle form submission more efficiently
        $.ajax({
            type: "POST",
            url: post_url,
            success: function (subcategories) //we're calling the response json array 'cities'
            {
                $('#sub_category').empty();
                $('#sub_category_h').show();
                $.each(subcategories, function (sc_id, sc_name)
                {
                    var opt = $('<option />'); // here we're creating a new select option for each group
                    opt.val(sc_id);
                    opt.text(sc_name);
                    $('#sub_category').append(opt);
                });
            } //end success
        }); //end AJAX
    } else {
        $('#sub_category').empty();
        $('#sub_category_h').hide();
    }//end if
}); //end change
});

这是验证器控制器...

              public function form_submit(){
                  //all form validation code goes here
              }
              public function get_cities($state){
      //this method is called from dropdown.js file to populate subcategory dropdown 
      //but when url changes... this function become unaccessible by dropdown.js     
                            header('Content-Type: application/x-json; charset=utf-8');
                            echo(json_encode($this->form_model->get_cities_by_state($state)));
                }
              public function get_sub_category($category){
      //this method is called from dropdown.js file to populate subcategory dropdown 
      //but when url changes... this function become unaccessible by dropdown.js                          
                            header('Content-Type: application/x-json; charset=utf-8');
                            echo(json_encode($this->form_model->get_subcategory_by_category($category)));
                }

}'

因此，当我提交表单以验证失败时，它会转到 url （http://localhost/ci_practice/index.php/validator/form_submit），然后 jquery 的 ajax 方法无法访问验证器控制器get_cities()方法和get_sub_category()方法，因此我无法重新填充我的下拉列表。如何处理这个问题？暂时我正在使用此解决方案

/**
     * For the time being, i am checking if the user has submitted the form  or not
     * By the following if else block but this is not a portable solution
     */
    if($(location).attr('href')=="http://localhost/ci_practice/"){  
        var post_url = "index.php/validator/get_cities/"+state_id;
    } else{
        var post_url ="get_cities/"+state_id;
    }

在我的外部JavaScript文件中，但我认为这不是一个可移植的解决方案。