reload combobox when it's depend field change in an common way

[yulei]

I add dependForm and dependFields attributes  to field collegeCode.

Code:

<form id="courseListForm" method="post">
	<input class="easyui-combobox" id="collegeCode"  name="collegeCode"  style="width:250px" 
		multiple="multiple"  valueField="code" textField="shortName"
		url='${appPath}/college/collegeListData.do'/>
	 
	<input class="easyui-combobox" id="collegeCode"  name="collegeCode"  style="width:250px" 
		multiple="multiple" dependForm="courseListForm" dependFields="termCode" valueField="code" textField="shortName"
		url='${appPath}/college/collegeListData.do'/>
	other fields...
</form>

after parser onComplete , I call the Component's extParse method if exits

Code:

$.parser.onComplete= function(context){
		for(var i=0; i<$.parser.plugins.length; i++){
			var name = $.parser.plugins[i];
			var r = $('.easyui-' + name, context);
			if (r.length){
				if (r[name]&&r[name].methods.extParse){
					r[name]('extParse');
				}  
			}
		}
}

then i extend an method to combobox

Code:

$.extend($.fn.combobox.methods, {
		extParse: function(jq){
			jq.each(function(){
				var _this = $(this);
				//default value
				var defaultExtOptions = {
					dependForm:null,
					dependFields:null,
				};
		        //markup value
				var markupOptions = {
					dependForm:_this.attr('dependForm'),
					dependFields:_this.attr('dependFields'),
				};
				
				//megre extOptions
		        var extOptions = $.extend(defaultExtOptions,markupOptions);
		        
		        if(extOptions.dependFields){
		        	//register event
		        	var  dependFields = extOptions.dependFields.split(',');
		        	for(var i in dependFields){
		        		//**************************************************
		        		$('#'+dependFields[i]).textbox('options').onChange=function(){
		        			_this.combobox('reload');
			        	};
		        	}
		        }
		        
		        if(extOptions.dependForm){
		        	_this.combobox({
		        		onBeforeLoad: function(param){
		        			var formData = $("#"+extOptions.dependForm).formToObject();
		        			$.extend(param,formData);
		        		}
		        	});
		        }
			});
	    }
	});

the line below many '*****',have errors,so the question is :
combobox extends combo
combo extends textbox.
can i call the parent's 'options' method to get the current options ?
because i can't know ,what the depended component type is