Help with scope issue using function

JamesCrandall — Mon, 13 Jun 2022 20:47:38 GMT

Having some difficulty with a seemingly simple scope issue that I am struggling to understand. Someone will probably be able to quickly identify what I'm missing here!

I have a function that calculates planar area and calculates an acreage value with the geometry of a graphic as the input parameter. In that process I intended to set "this.acrevalue" and have it set and available later on in other functions of a button click event. However, it's always null BUT I can see that the correct acreage value is being calculated.

saveDataBtnClick() function is a button in the html of the widget that I hoped to somehow use the getAcreageValueFromPolygon() function to get the acreage value before submitting a applyEdit() on the feature service.

getAcreageValueFromPolygon: function (geom) { projection.load().then(function (evt) { const inSpatialReference = new SpatialReference({ wkid: 102100 }); const spSpatialReference = new SpatialReference({ wkid: 2881 }); const poly = new Polygon(geom, inSpatialReference); var geoT = projection.getTransformation(inSpatialReference, spSpatialReference) const projectedPoly = projection.project(poly, spSpatialReference); var areasAndLengthParams = new AreasAndLengthsParameters(); areasAndLengthParams.areaUnit = esri.tasks.GeometryService.UNIT_ACRES; areasAndLengthParams.lengthUnit = GeometryService.UNIT_FOOT; areasAndLengthParams.polygons = projectedPoly; var geometryService = new GeometryService("https://utility.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer"); geometryService.on("areas-and-lengths-complete", outputAreaAndLength); geometryService.simplify([projectedPoly], function (simplifiedGeometries) { areasAndLengthParams.polygons = simplifiedGeometries; geometryService.areasAndLengths(areasAndLengthParams); }); }.bind(this)) function outputAreaAndLength(evtObj) { var result = evtObj.result; this.acrevalue = result.areas[0].toFixed(3) } }, saveDataBtnClick: function () { var e = document.getElementById("layerTypeSelections"); //use config to reference services and specific service layers this.serverSideScratchLayer = new FeatureLayer(this.config.applicationFeatureLayer + "/" + lyrNum, { outFields: ["*"] }); var features = this.unionedGraphic2.geometry if (features) { this.getAcreageValueFromPolygon(this.unionedGraphic2.geometry); //set the acreagae value and have it available for saving in applyEdits var spAcres = this.acrevalue; attr["TRMT_ACRES"] = spAcres; var fYear = '1901' attr['FISCAL_YEAR'] = fYear this.unionedGraphic2["attributes"] = this.attr this.serverSideScratchLayer.applyEdits([this.unionedGraphic2], [], this.attr, lang.hitch(this, function (add) { if (add.length > 0) { if (add[0].objectId) { console.log('Add successful with objectid: ' + add[0].objectId); this.uploadOID = add[0].objectId } } }).bind(this)); } },

Re: Help with scope issue using function

KenBuja — Tue, 14 Jun 2022 12:43:50 GMT

When using "this" in a function, you have to use "lang.hitch" to make sure "this" is retaining the proper scope.

geometryService.on("areas-and-lengths-complete", lang.hitch(this, outputAreaAndLength));

Re: Help with scope issue using function

JamesCrandall — Tue, 14 Jun 2022 13:19:21 GMT

I must have put that in just about every place except where you suggest. LOL --- thank you, this resolves the issue (although not sure if it resolves the issue that I consistently struggle with scope).

Much appreciated!

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Help with scope issue using function

Re: Help with scope issue using function

Re: Help with scope issue using function