如何修复TypeError：在ArcGIS JS API（查询）中未定义this._url

Question

I'm tasked with developing a custom widget for ArcGIS' Web App Builder and i've been trying to get a Query to work using the ArcGIS Javascript API 3.28 so i can build a report using layer information. But upon attempting to test the query by means of a button, i get a TypeError: this._url is undefined.

define(['dojo/_base/declare', 'jimu/BaseWidget',
        'jimu/dijit/Report', 'esri/layers/FeatureLayer',
        'jimu/dijit/PageUtils', 'dijit/_WidgetsInTemplateMixin', 'esri/tasks/IdentifyTask',
        'esri/tasks/IdentifyParameters', 'esri/symbols/SimpleFillSymbol', 'esri/symbols/SimpleLineSymbol',
        'esri/graphic', 'esri/Color', 'dojo/_base/lang',
        'dojo/_base/html', 'dojo/on', 'dojo/domReady!',
        'esri/tasks/QueryTask', 'esri/tasks/query'],

function(declare, BaseWidget, Report, FeatureLayer,
        PageUtils, _WidgetsInTemplateMixin, IdentifyTask, IdentifyParameters,
        SimpleFillSymbol, SimpleLineSymbol, Graphic,
        Color, lang, on, Query, QueryTaskTest) {

  var baseWidgetClass = declare([BaseWidget], {
    baseClass: 'jimu-widget-demo',

    postCreate: function() { // POST CREATE!
      this.inherited(arguments);
      this.map.infoWindow.hide();
    },

    startup: function() {
      this.inherited(arguments);
      console.log('startup');
    },

    onClose: function(){
      console.log('onClose');
    },

    _onBtnPrintClicked: function(){
    console.log("Begin query test");
    var queryUrl = "https://webportalurl/arcgis/rest/services/ServiceName/MapServer/0";
    var queryTask = new QueryTaskTest(queryUrl);
    var query = new Query();
    query.returnGeometry = false;
    query.outFields = ["*"];
    query.where = "HAB_IPTU = 2089358";
    console.log("Running execute");

    queryTask.execute(query).then(function(results){
      console.log(results.features[0]);
    });
  }

  });
  return baseWidgetClass;
});

Answer 1

QueryTask on api 3.28 expects the url as String : https://developers.arcgis.com/javascript/3/jsapi/querytask-amd.html#querytask1

Try this :

var queryTask = new QueryTask(queryUrl);

or

var queryTask = new QueryTask("MapServerUrl");

Answer 2

The problem has nothing to do with the QueryTask or how you are calling it. The arguments in the define statement and function definition do not match up.

'dojo/_base/lang', matches up with lang in the function but then 'dojo/_base/html' matches up with the on, 'dojo/on' matches up with Query and finally 'dojo/domReady!' matches up with QueryTaskTest. use the modules that don't require a corresponding constructor at the end of the define list otherwise you have to include them in the function definition to preserve the order.

like this

    define(['dojo/_base/declare',
        'jimu/BaseWidget',        
        'jimu/dijit/Report', 
        'esri/layers/FeatureLayer',
        'jimu/dijit/PageUtils',
        'dijit/_WidgetsInTemplateMixin',
        'esri/tasks/IdentifyTask',
        'esri/tasks/IdentifyParameters', 
        'esri/symbols/SimpleFillSymbol', 
        'esri/symbols/SimpleLineSymbol',
        'esri/graphic', 
        'esri/Color', 
        'dojo/_base/lang',
        'dojo/on',        
        'esri/tasks/query',
        'esri/tasks/QueryTask',
        'dojo/_base/html', //these last two are at the end
        'dojo/domReady!'], //because they don't need to be called or instantiated directly.

    function(declare, 
        BaseWidget, 
        Report, 
        FeatureLayer,
        PageUtils, 
        _WidgetsInTemplateMixin,
        IdentifyTask,
        IdentifyParameters,
        SimpleFillSymbol,
        SimpleLineSymbol,
        Graphic,
        Color,
        lang,
        on,
        Query,
        QueryTaskTest) { ....});