topic Re: Target must be an event emitter in ArcGIS JavaScript Maps SDK Questions

Target must be an event emitter

MattTenold — Sat, 11 Dec 2021 14:48:52 GMT

I am currently using the Dojo/on and I keep receiving the Error: Target must be an event emitter
http://js.arcgis.com/3.9/
Line 212

error in this function:

function runQuery() {
   var queryTask = new esri.tasks.QueryTask("http://gis.phila.gov/ArcGIS/rest/services/PhilaGov/Police_Incidents_Last30/MapServer/0");
   
   var query = new esri.tasks.Query();
   query.returnGeometry = true;
   query.where = '1=1';
   query.outFields = ["DC_DIST", "POINT_X", "POINT_Y"];
   
   map.on(queryTask, "onComplete", function(featureSet) {

    var cL = new clusterlayerNew({
     displayOnPan: false,
     map: map,
     features: featureSet.features,
     infoWindow: {
      template: new esri.InfoTemplate("${SECTOR}"),
      width: 325,
      height: 100
     },
     flareLimit: 15,
     flareDistanceFromCenter: 20
       });

             map.addLayer(cL);

   });
  };

Re: Target must be an event emitter

DasaPaddock — Tue, 15 Apr 2014 17:56:26 GMT

Try: queryTask.on("complete", function(event) {});

See:
https://developers.arcgis.com/javascript/jsapi/querytask-amd.html#event-complete

Re: Target must be an event emitter

MattTenold — Tue, 15 Apr 2014 18:18:04 GMT

I can't do

queryTask.on("complete", function(event) {});

since I am constructing a clusterlayer using the function features from my AMD class "clusterlayerNew." Is there a way to get the features from the function "features" while running after the queryTask is complete?

Re: Target must be an event emitter

ReneRubalcava — Tue, 15 Apr 2014 18:35:31 GMT

How about

on(queryTask, 'complete', function(){});

You lost me there, but the execute method returns a Promise, so you can also do.

queryTask.execute(query).then(someFunction);

Re: Target must be an event emitter

DasaPaddock — Sat, 11 Dec 2021 14:48:54 GMT

How about this?

function runQuery() {
  var queryTask = new esri.tasks.QueryTask("http://gis.phila.gov/ArcGIS/rest/services/PhilaGov/Police_Incidents_Last30/MapServer/0");

  var query = new esri.tasks.Query();
  query.returnGeometry = true;
  query.where = '1=1';
  query.outFields = ["DC_DIST", "POINT_X", "POINT_Y"];

  queryTask.on("complete", function(event) {

    var cL = new clusterlayerNew({
      displayOnPan: false,
      map: map,
      features: event.featureSet.features,
      infoWindow: {
        template: new esri.InfoTemplate("${SECTOR}"),
        width: 325,
        height: 100
      },
      flareLimit: 15,
      flareDistanceFromCenter: 20
    });

    map.addLayer(cL);

  });
};

Re: Target must be an event emitter

MattTenold — Sat, 11 Dec 2021 14:48:57 GMT

I tried both methods. But this won't work either. The main problem is all of my events are handled in my Dojo class. I attached the main html page and the dojo class with the logic that the main page accesses.

function runQuery() {
   var queryTask = new esri.tasks.QueryTask("http://gis.phila.gov/ArcGIS/rest/services/PhilaGov/Police_Incidents_Last30/MapServer/0");
   
   var query = new esri.tasks.Query();
   query.returnGeometry = true;
   query.where = '1=1';
   query.outFields = ["DC_DIST", "POINT_X", "POINT_Y"];
   
   queryTask.on("complete", function(event) {

    var cL = new clusterlayerNew({
     displayOnPan: false,
     map: map,
     features: event.featureSet.features,
     infoWindow: {
      template: new esri.InfoTemplate("${SECTOR}"),
      width: 325,
      height: 100
     },
     flareLimit: 15,
     flareDistanceFromCenter: 20
       });

             map.addLayer(cL);

   });
  };

Re: Target must be an event emitter

DasaPaddock — Tue, 15 Apr 2014 19:02:08 GMT

I just noticed that `runQuery` is missing a call to `queryTask.execute(query)`. Can you try adding this before the queryTask.on line?

Re: Target must be an event emitter

MattTenold — Tue, 15 Apr 2014 21:57:20 GMT

Tried that also. Didn't work. It keeps saying Target must be an event emitter.

Re: Target must be an event emitter

DasaPaddock — Sat, 11 Dec 2021 14:49:00 GMT

Is this code still in the html page?

  on(queryTask, "onError", function(err) {
  alert(err.details);
  });

  queryTask.execute(query);

Can you remove it since outside the runQuery function, queryTask is the esri/tasks/QueryTask module rather than an instance of a QueryTask.

Re: Target must be an event emitter

MattTenold — Wed, 16 Apr 2014 16:20:14 GMT

Tried that. It runs but it keeps jumping around. It doesn't go through the functions. It is really weird. I set a break point but it won't step through the functions. I am still looking for why it doesn't continue running through the functions.

Re: Target must be an event emitter

ReneRubalcava — Sat, 11 Dec 2021 14:49:02 GMT

Ok, I got this working, somewhat, but I'll get to that.

This works.

require([
    "dojo/Evented",
    "dojo/ready",
    "dojo/parser",
    "dojo/on",
    "extras/clusterlayerNew",
    "esri/map",
    "esri/layers/graphics",
    "esri/layers/FeatureLayer",
    "esri/layers/GraphicsLayer",
    "esri/tasks/QueryTask",
    "esri/tasks/query",
    "dijit/layout/BorderContainer",
    "dijit/layout/ContentPane",
    "dojo/domReady!"
  ],
  function (
    Evented,
    ready,
    parser,
    on,
    ClusterlayerNew,
    Map, // you had lower-case map, which can cause problems when creating a map variable
    graphics, // This is an empty object because it is not a module
    FeatureLayer,
    GraphicsLayer,
    QueryTask, // was called queryTask, biggest issue
    Query,
    BorderContainer,
    ContentPane
  ) {

    var map;
    // scope this out here. The above had same name (case matters).
    var queryTask = new QueryTask("http://gis.phila.gov/ArcGIS/rest/services/PhilaGov/Police_Incidents_Last30/MapServer/0");


    function init() {
      parser.parse();

      map = new Map("map", { // You had map = new map(), this could cause issues, probably in IE, everything breaks in IE.
        center: [-75.1700, 39.9500],
        zoom: 12,
        basemap: "hybrid"
      });
      runQuery(); // you need the map in the runQuery method, so initialize it first then do runQuery
    }

    function runQuery() {
      var query = new Query();
      query.returnGeometry = true;
      query.where = '1=1';
      query.outFields = ["DC_DIST", "POINT_X", "POINT_Y"];

      queryTask.on("complete", function (event) {
        console.debug('ClusterlayerNew is an empty object?', ClusterlayerNew);
        // This clusterlayer module is broken, it returns an empty object, even after I quickly edited it.
        // I did not try troubleshooting this
        var cL = new ClusterlayerNew({
          displayOnPan: false,
          map: map,
          features: event.featureSet.features,
          infoWindow: {
            template: new esri.InfoTemplate("${SECTOR}"),
            width: 325,
            height: 100
          },
          flareLimit: 15,
          flareDistanceFromCenter: 20
        });

        map.addLayer(cL);

      });
      // you were trying to execute this outside the scope of the function the query was defined in.
      queryTask.execute(query); 
    };

    // before, this was the class "QueryTask", the class is not initialized, thus not an event emitter.
    on(queryTask, "error", function (err) {
      alert(err.details);
    });

    // Use the ready() method as opposed to dojo.addOnLoad
    ready(init);
  });

See my comments for some of the issues you had.

One of your main issues seems to be with scope, so I would run through some material and you'll soon see where things broke.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions_and_function_scope

Don't mix the old dojo.lib.ClassName() with the AMD loading of modules. In this case, it probably just added to the confusion.
Note - Mixing the two won't necessarily break your code (yet), but it should be avoided fro consistency.
That clusterlayerNew module is broken or something, I couldn't get it to work, but my changes above load your map and at least try to create that cluster layer.

You may want to check out a project I have been working on to do clusters in a fashion more similar to a FeatureLayer.
https://github.com/odoe/esri-clusterfeaturelayer

Hope that helps a bit.

Re: Target must be an event emitter

MattTenold — Wed, 16 Apr 2014 20:19:53 GMT

Cool. Thank you soo much Odoe. The clusterlayerNew.js isn't soo much of a big deal. I am going to have to use use a json feed anyways which means I will have to modify the clusterlayerNew.js class alot.