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Populate featureTable with centroid only geometry from feature service

ForrestKaye

Hello,

I was wondering if it is possible to populate a FeatureTable from a Feature Service with the centroid only geometry. Looking through the documentation and attempting this does not make it seem possible with the maps SDK. I could do it by pinging the FeatureService directly and using the returnCentroid parameter but that does not seem to be exposed in the SDK.

If this is not possible can I put an enhancement request in for it? Use case is this: Querying polygon features hosted in a service. I do not want to return the entire geometry for performance reasons. I want to sort the features by nearest location to the user. Having access to the centroid would satisfy my sorting and performance needs.

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ForrestKaye

Hi Ting,

So for my intended workflow those will not work for me as I am populating my feature table with null geometries (queryParameters.returnGeometry = false) So will not have any geometry to get either the label point or the envelop center.

At first I had thought that some bare bones spatial data (label point or envelop center) did come through on the query even if the returnGeometry = null. But that does not seem to be the case.

My Hope was that I could get a minimal about of spatial data on my polygon so I can then sort them via distance to my users. This would keep my queries performant as the geometries are quite complex and also avoid errors I had seen on the service alerting me too many queries had been performed querying complex geometries and would need to wait 60 seconds before performing more queries.

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Ting

Hi Forrest, thanks for posting. You are right, currently our SDK doesn't support the returnCentroid parameter.

Some (SDK-client-side) alternatives that may be worth a try: GeometryEngine.labelPoint(for:), or Envelope.center, for a rough estimate if the polygon is simple.

As they may not be suitable for your use case, please feel free to post in Native SDKs Ideas with your use case.

ForrestKaye

Hi Ting,

At first I had thought that some bare bones spatial data (label point or envelop center) did come through on the query even if the returnGeometry = null. But that does not seem to be the case.

Ting

Thanks for explaining your use case. I agree that not to fetch the complex geometry is a big time saver. Unfortunately, we haven't quite matched up with all the parameters that the REST API provides yet.

So if you want this feature, a few options to consider:

Create a feature request in Native SDKs Ideas board with your use case. Thus, this feature request can be triaged by our PMs.
Maybe include a pre-computed field in the feature table for the centroid, if you have control over that feature table.
Make a raw URLRequest to the REST API endpoint, and parse the response as you need. The URL structure for the GET request is relatively straightforward: https://YOUR_FEATURE_SERVER/FeatureServer/0/query?f=json&outFields=OBJECTID,STATE_NAME&where=1%3D1&outSR=4326&returnDistinctValues=false&returnGeometry=false&returnM=false&returnZ=false&returnCentroid=true&token=YOUR_API_KEY
- simply swap the feature server and API key from the URL
- or create the request in Swift such as

let baseURL = URL(string: "https://…/FeatureServer/0/query")!
var components = URLComponents(url: baseURL, resolvingAgainstBaseURL: false)!
components.queryItems = [
    URLQueryItem(name: "f", value: "json"),
    URLQueryItem(name: "outFields", value: "OBJECTID,STATE_NAME"),
    URLQueryItem(name: "where", value: "1=1"),
    URLQueryItem(name: "outSR", value: "4326"),
    URLQueryItem(name: "returnDistinctValues", value: "false"),
    URLQueryItem(name: "returnGeometry", value: "false"),
    URLQueryItem(name: "returnM", value: "false"),
    URLQueryItem(name: "returnZ", value: "false"),
    URLQueryItem(name: "returnCentroid", value: "true"),
    URLQueryItem(name: "token", value: "YOUR_API_KEY")
]
guard let finalURL = components.url else {
    fatalError("Invalid URL components")
}
var request = URLRequest(url: finalURL)
request.httpMethod = "GET"

It is possible to use DataTaskInterceptor to intercept the query response and get the centroids from there, but I don't recommend doing that to introduce some fragile code logics. Nonetheless, I sent you a DM with a code snippet in case you want to give it a try.

ForrestKaye

Thank you for the detailed and thorough response. I'm not quite sure the route we'll go but I think you pretty much covered all options there. Thank you. I will be putting in a request for that via in the native SDK's Ideas.

Cheers!

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