Query points with in multiple Polygon Geometries

ChristianDebono

I have a layer containing a set of points and another layer with polygons. I have queried the points in a single polygon with no problems. Now I want to query these points  with multiple polygon selection; i.e. the user clicks on the polygons which he wants to query and then selects the functionality to query these polygons. Currently, I am doing this procedure as the user clicks the polygons and array is populated with the geometries of the polygons and I looping through this array and query with the geometries.

for (var ai = 0; ai < multiplePolygons.length; ai++) {
    var query = new Query();
    var queryTask = new QueryTask(pointUrl);
    query.geometry = multiplePolygons[ai].areaGeometry;
    query.returnGeometry = true;
    query.outFields = ["*"];
                    
    queryTask.execute(query, function (results) {     
         for (var i = 0; i < results.features.length; i++) {
               var qResult = results.features.attributes["Attribute"];
         }
    });
}

Is there a more conventional way in order to query multiple polygons?

OwenEarley

The ideal solution would be if the query.geometry property took an array as input. However the documentation seems to indicate that it is only a single geometry.

You could look into promises - check out the last example on this page: dojo/promise/all — The Dojo Toolkit - Reference Guide‌

The trick would be creating the Object that you provide as a parameter dynamically using your multiple polygons. Possibly something like this untested code:

// 1. make sure to add required modules ("dojo/promise/all", "dojo/Deferred", etc )

// 2. dynamically build object for dojo/promise/all parameter
queries = {};
for (var ai = 0; ai < multiplePolygons.length; ai++) { 
    var qryName = "qry" + ai;
    queries[qryName] = queryPolygon(multiplePolygons[ai].areaGeometry);
}

// 3. return a deferred object from each query
function queryPolygon(geom) {
    var deferred = new Deferred();
    var query = new Query();  
    var queryTask = new QueryTask(pointUrl);  
    query.geometry = geom;  
    query.returnGeometry = true;  
    query.outFields = ["*"];                        
    queryTask.execute(query, function (results) {  
        deferred.resolve(results);
    });
    return deferred.promise;
};

// 4. use all to process each polygon then respond to final results
all({queries}).then(function(results){
    // process your final results here
    console.log("All Results: ", results);
});

Please note that I haven't used promises/deferred in dojo, but I have had great success in AngularJS using them.

Owen

Spatial XP