Polymorphism?

[SebastianStehle]

Have you not handled polymorphism? I do not see converters for GeoJSONObject ot the interfaces.

[matt-lethargic]

Can you give me an example of what can't be done without this converter so I can understand the issue a little better?

[SebastianStehle]

Lets say, I have the following request definition:

class CreateGeometry
{
 [Required]
 public GeoJsonObject Geometry {get; set; }
}

So the user can either give in a point or circle or polygon or whatever.

I don't see how this is possible at the moment and I also tested it and got an error.

[MartinCarpentier]

What you want works by using the geometry interface.

IGeometryObject

[SebastianStehle]

Oh, sorry ... have not seen that. Why is there both a interface and a abstract class?

[MartinCarpentier]

I sadly do not know, since i have not been a part of the initial implementation of the library, i just converted it to system.text.json, but i guess the abstract class exists to share common properties to all of the geometry object types.
Maybe it should be internal, since it makes no sense to use it externally.

[andreas-foreflight]

Is there a way to get this to work with any GeoJson object, not only geometry types (i.e. also Feature and Feature Collection). Using IGeoJsonObject does not seem to work?

I would like to serialize any type of geoJson object, but this does not work:

>>> System.Text.Json.JsonSerializer.Serialize((GeoJSON.Text.IGeoJSONObject)source.Data)
"{\"type\":8,\"crs\":null,\"bbox\":null}"

I can properly serialize it as a feature collection, but this is not polymorphic:

>>> System.Text.Json.JsonSerializer.Serialize((FeatureCollection)source.Data)
"{\"type\":\"FeatureCollection\",\"features\":[{\"type\":\"Feature\",\"geometry\":{\"type\":\"LineString\",\"coordinates\":[[90,50],[25,0]]},\"properties\":{}}]}"

Using IGeometryObject is not an option, because not all GeoJson objects are geometry objects:

>>> System.Text.Json.JsonSerializer.Serialize((IGeometryObject)source.Data)
'System.Text.Json.JsonSerializer.Serialize((IGeometryObject)source.Data)' threw an exception of type 'System.InvalidCastException'
    Data: {System.Collections.ListDictionaryInternal}
    HResult: -2147467262
    HelpLink: null
    InnerException: null
    Message: "Specified cast is not valid."
    Source: "006cbf0666ad4386b97cab13a906b566"
    StackTrace: "   at <>x.<>m0(<OnLoad>d__4 <>4__this)"
    TargetSite: {System.String <>m0(<OnLoad>d__4)}

[hu-xd]

ditto. need to parse GeoJson data without knowing beforehand whether it is a geometry or feature or feature collection etc. how ?

[crozone]

It looks like this is within reach, it just requires another converter for the top level IGeoJSONObject which can switch internally on GeoJSONObjectType, similar to how the polymorphic IGeometryObject converter works:

GeoJSON.Text/src/GeoJSON.Text/Converters/GeometryConverter.cs

Lines 86 to 107 in 31ec322

	switch (geoJsonType)
	{
	case GeoJSONObjectType.Point:
	return value.Deserialize<Point>(options);
	case GeoJSONObjectType.MultiPoint:
	return value.Deserialize<MultiPoint>(options);
	case GeoJSONObjectType.LineString:
	return value.Deserialize<LineString>(options);
	case GeoJSONObjectType.MultiLineString:
	return value.Deserialize<MultiLineString>(options);
	case GeoJSONObjectType.Polygon:
	return value.Deserialize<Polygon>(options);
	case GeoJSONObjectType.MultiPolygon:
	return value.Deserialize<MultiPolygon>(options);
	case GeoJSONObjectType.GeometryCollection:
	return value.Deserialize<GeometryCollection>(options);
	case GeoJSONObjectType.Feature:
	case GeoJSONObjectType.FeatureCollection:
	default:
	throw new NotSupportedException("Feature and FeatureCollection types are Feature objects and not Geometry objects");
	}