Adding points to map object using dojo xhr.get web service call

SEISMaster

I would like to add graphics to a map based on data from a web service call. This is the code I have:

var xhrArgs = {
                            url: "/Map/getalerts",
                            handleAs: "json",
                            load: function (track) {
                                var point = new Point(track.Latitude, track.Longitude, new SpatialReference({ wkid: 4326 }));
                                var simpleMarkerSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 10, new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
                                   new Color([255, 0, 0]), 1),
                                   new Color([0, 255, 0, 0.25]));
                                var graphic = new Graphic(webMercatorUtils.geographicToWebMercator(point), simpleMarkerSymbol,
                                 { 'title': track.FullName, 'content': 'ID: 2<br/>TimeStamp: Some Time<br/>Message Type: Alert' },
                                new InfoTemplate('${title}', '${content}'));
                                this.map.graphics.add(graphic);

                            },
                            error: function (error) {
                                console.log("An unexpected error occurred: " + error);
                            }
                        }

                        // Call the asynchronous xhrGet
                        var deferred = xhr.get(xhrArgs);
          }

However, when the call returns this.map is no longer in scope and the javascript throws an error about it being undefined.

Does anyone have any idea about how I can get hold of the map object again when the data from the web service call has been returned?

JasonZou

Below solution assumes that in the scope where xhrArgs is defined, this.map can be accessible.

Add a local variable 'self' to host the context where xhrArgs is defined, then use self.map inside the callback function based on closure.

var self = this; var xhrArgs = {     url: "/Map/getalerts",     handleAs: "json",     load: function (track) {         var point = new Point(track.Latitude, track.Longitude, new SpatialReference({             wkid: 4326         }));         var simpleMarkerSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 10, new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,                 new Color([255, 0, 0]), 1),             new Color([0, 255, 0, 0.25]));         var graphic = new Graphic(webMercatorUtils.geographicToWebMercator(point), simpleMarkerSymbol, {                 'title': track.FullName,                 'content': 'ID: 2<br/>TimeStamp: Some Time<br/>Message Type: Alert'             },             new InfoTemplate('${title}', '${content}'));         self.map.graphics.add(graphic);      },     error: function (error) {         console.log("An unexpected error occurred: " + error);     } }