Need help with polygon union operation using JavaScript 3.6 API with undo, redo

[ThomasRoussell]

I am trying to implement a polygon union operation using ArcGIS 10.2 JavaScript 3.6 API with undo, redo capabilities. I am able to perform the union operation, but when I try to undo the operation I get the following error:

Unhandled exception at line 19, column 1879 in http://js.arcgis.com/3.6/js/esri/dijit/editing/Cut.js

0x800a138f - JavaScript runtime error: Unable to get property 'length' of undefined or null reference

Code Snippet:

dojo.connect(dijit.byId("Merge_Button"), "onClick", function () {     editing_function = "Merge_From";     document.getElementById("Status_Message").innerHTML = "Select Polygon to Merge From"     esri.bundle.toolbars.draw.addPoint = "Select Polygon to Merge From";     drawToolbar.activate(esri.toolbars.Draw.POINT); });  dojo.connect(drawToolbar, "onDrawEnd", function (geometry) {  if (editing_function == "Merge_From") {     var point_selectQuery = new esri.tasks.Query();     point_selectQuery.geometry = geometry;      edit_featurelayer.selectFeatures(point_selectQuery, esri.layers.FeatureLayer.SELECTION_NEW, function (features) {         if (features.length == 0) {             r = confirm("Nothing Selected. Try again?");             if (r == true) {                 return;             }             drawToolbar.deactivate();             document.getElementById("Status_Message").innerHTML = "Nothing exciting going on around here";             return         }         merge_from_features = features;         editing_function = "Merge_To";         document.getElementById("Status_Message").innerHTML = "Select Polygon to Merge To";         esri.bundle.toolbars.draw.addPoint = "Select Polygon to Merge To";     });     return; }  if (editing_function == "Merge_To") {     var point_selectQuery = new esri.tasks.Query();     point_selectQuery.geometry = geometry;     edit_featurelayer.selectFeatures(point_selectQuery, esri.layers.FeatureLayer.SELECTION_ADD, function (features) {         if (features.length == 0) {             r = confirm("Nothing Selected. Try again?");             if (r == true) {                 return;             }             drawToolbar.deactivate();             document.getElementById("Status_Message").innerHTML = "Nothing exciting going on around here";             return         }         merge_to_features = features;         editing_function = "";         document.getElementById("Status_Message").innerHTML = "Nothing exciting going on around here";         drawToolbar.deactivate();          var input_geometries;         try {              var from_g = merge_from_features[0].geometry;             var to_g = merge_to_features[0].geometry;             var input_geometries = [from_g, to_g];              geometryService.union(input_geometries, function (unioned_geometry) {                 var merge_from_feature = merge_from_features[0];                 var merge_to_feature = merge_to_features[0];                  var original_feature = merge_to_feature.toJson();                 merge_to_feature.geometry = unioned_geometry;                  edit_featurelayer.applyEdits(null, [merge_to_feature], [merge_from_feature], function () {                     try {                          var operation = new esri.dijit.editing.Union({                             deleted_graphics: [merge_from_feature],                             featureLayer: edit_featurelayer,                             preUpdatedGraphics: new esri.Graphic(original_feature),                             postUpdatedGraphics: [merge_to_feature]                         });                      }                     catch (err) {                         alert(err.message);                     };                     undoManager.add(operation);                     checkUI();                 });             });         }         catch (err) {             alert(err.message);         };     });       return; };  drawToolbar.deactivate();

[JasonZou · Accepted solution]

Change:

var operation = new esri.dijit.editing.Union({     deleted_graphics: [merge_from_feature],     featureLayer: edit_featurelayer,     preUpdatedGraphics: new esri.Graphic(original_feature),     postUpdatedGraphics: [merge_to_feature] });

To:

var operation = new esri.dijit.editing.Union({     deletedGraphics: [merge_from_feature],     featureLayer: edit_featurelayer,     preUpdatedGraphics: [new esri.Graphic(original_feature)],     postUpdatedGraphics: [merge_to_feature] });

[ThomasRoussell]

Thank you Jason. That fixed the problem.

Tom

[ThomasRoussell]

In case anyone is interersted, there was one more problem with the code. I needed to reverse the preUpdatedGraphics and the postUpdatedGraphics.

                                        
var operation = new esri.dijit.editing.Union({
    deletedGraphics: [merge_from_feature],
    featureLayer: edit_featurelayer,
    postUpdatedGraphics: [new esri.Graphic(original_feature)],
    preUpdatedGraphics: [merge_to_feature]
});