Selecting multiple features with rectangle using ArcGIS API for JavaScript?

Question

I am using ArcGIS API for JavaScript 3.7.

I am trying to see if I can select features in the same fashion that shift+click and dragging lets you zoom into the map by drawing a rectangle. The trouble that I am encountering is that I want this functionality on a certain layer of the map, but I do not know if this layer is ready yet. I've tried using the following:

map.on('load', function initSelectToolbar(event) {
    selectionToolbar = new Draw(event.map);
    var selectQuery = new Query();

    on(selectionToolbar, "DrawEnd", function (geometry) {
        selectionToolbar.deactivate();
        selectQuery.geometry = geometry;
        featureLayer.selectFeatures(selectQuery, FeatureLayer.SELECTION_NEW);
    });
});

I would like to see if it is possible to run this code when I know for sure that the layer is ready. As far as I am aware, I can't change the feature layer the code references once it is loaded in.

EDIT: It looks like I got it to work. I found a way to grab the layers URL using map.getLayer(layerId).url (how I missed that is beyond me), created a new feature layer for selection, and removed it when the user was done. I still think this could be done better though.

Answer 1

You can check if a specific layer is loaded (using map.addLayer) with the map's layer-add-result event. Since this event fires when any layer is loaded (including the basemaps), you have to check for the specific layer

map.addLayer(featureLayer);
map.on('layer-add-result', function(addLayer){
  if (addLayer.layer === featureLayer){
    console.log(featureLayer);
  }
});

If you're using map.addLayers to add multiple layers, you can use the layers-add-result event

map.addLayers([featureLayer]);
map.on('layers-add-result', function (){
  console.log(featureLayer);
});