topic Re: creating a filter (query?) in Open Source Mapping Libraries Ques.

creating a filter (query?)

joepublic — Mon, 28 Aug 2023 13:10:01 GMT

I am using esri's feature service and ersi-leaflet library to display my map. The following code snippet is used to display

the countries

featureURL = "http://dev.xxxxx.org/arcgis/rest/services/MEP/noRelate_tester/FeatureServer/0"

var countries = L.esri.featureLayer(featureURL,

{

style: getStyle,

onEachFeature: onEachFeature

}).addTo(map);

At this time, it is displaying all the countries.

I'd like to display (or highlight) only the countries that satisfies a certain filter or query.

For example, I want to display only the countries that satisfy the filter/query type = SDG.

I reviewed the docs and examples for esri-leaflet library but am totally lost as to how use the query method.

Can someone point me to an example that show how to use the filter/query to do the above

Thanks

Chris

Re: creating a filter (query?)

WinstonHoyle — Sun, 12 Dec 2021 08:49:01 GMT

The query method has examples on Esri Leaflet.

Example 1: https://esri.github.io/esri-leaflet/examples/querying-feature-layers-1.html

Example 2: https://esri.github.io/esri-leaflet/examples/querying-feature-layers-2.html

From Esri Leaflet Issues, I found a problem similar to yours.

Since you pass a GeoJSON feature you have access to attributes, like the "filter" attribute.

function filter(feature) {
   return feature.properties.type === "SDG";
}

var countries = L.esri.featureLayer(featureURL,{
  filter: filter,
  style: getStyle,
  onEachFeature: onEachFeature
}).addTo(map);‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Issue #214: https://github.com/Esri/esri-leaflet/issues/214

Re: creating a filter (query?)

JohnGravois — Tue, 17 Jul 2018 17:02:50 GMT

instead of fetching all the features from the service and filtering on the client, it's a better to only ask ArcGIS Online/Server for the features you want (using the where constructor option).

L.esri.featureLayer({

url: "http://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/3",

where: "STATE_NAME = 'Kansas'",

}).addTo(map);

Querying features | Esri Leaflet