topic Re: What is FeatureLayer selection for? in ArcGIS API for Flex Questions

What is FeatureLayer selection for?

DavidElies — Tue, 09 Nov 2010 22:44:38 GMT

I'm trying to use the FeatureLayer.selectedFeatures to run a query, but I don't know how to get the geometry. So, my questions are multiple:

What are the selectedFeatures supposed to be used for anyway?

Can I get the geometry from selected features?

Is there a way to get the geometry from multiple polygons?

Thanks so much!

Re: What is FeatureLayer selection for?

DasaPaddock — Tue, 09 Nov 2010 23:03:16 GMT

It's usually used in editing scenarios. You first have to select the features using:
http://help.arcgis.com/en/webapi/flex/apiref/com/esri/ags/layers/FeatureLayer.html#selectFeatures()

Re: What is FeatureLayer selection for?

DavidElies — Wed, 10 Nov 2010 16:57:14 GMT

Thanks for the reply, dpaddock!

Because of the simplicity of selecting, I thought it would be the answer to my dillema, but perhaps it isn't. Is it possible to get the union of Polygons? It looks like there is a union function for Extents, but since it returns an Extent, I assume it just returns the bounding box that contains both Extents, (which would include a lot more area than I want). I was really hoping to use the geometry of disconnected polys in a query. Is this even possible?

Re: What is FeatureLayer selection for?

DasaPaddock — Wed, 10 Nov 2010 17:12:40 GMT

You can query with a multi-ring polygon by setting Query.geometry.
http://help.arcgis.com/en/webapi/flex/apiref/com/esri/ags/geometry/Polygon.html
http://help.arcgis.com/en/webapi/flex/apiref/com/esri/ags/tasks/supportClasses/Query.html#geometry

Also, the GeometryService does have a union() method:
http://help.arcgis.com/en/webapi/flex/apiref/com/esri/ags/tasks/GeometryService.html#union()

Re: What is FeatureLayer selection for?

DavidElies — Wed, 10 Nov 2010 18:44:06 GMT

Thanks dpaddock!

I didn't realize that polygons naturally supported multiple disjoint shapes. I didn't understand what the rings were. I added each ring from my selected polygons to a "master" polygon and used that as the geometry for the query! This is exactly what I was looking for. Thanks so much!