feature function

Map<String?, dynamic> feature(Map<String?, dynamic> topology, Map<String?, dynamic> object)

Returns the GeoJSON Feature or FeatureCollection for the specified object in the given topology.

If the object is a GeometryCollection, a FeatureCollection is returned, and each geometry in the collection is mapped to a Feature. Otherwise, a Feature is returned. The returned feature is a shallow copy of the source object: they may share identifiers, bounding boxes, properties and coordinates.

Some examples:

• A point is mapped to a feature with a geometry object of type “Point”.
• Likewise for line strings, polygons, and other simple geometries.
• A null geometry object (of type null in TopoJSON) is mapped to a feature with a null geometry object.
• A geometry collection of points is mapped to a feature collection of features, each with a point geometry.
• A geometry collection of geometry collections is mapped to a feature collection of features, each with a geometry collection.

Implementation

Map<String?, dynamic> feature(
        Map<String?, dynamic> topology, Map<String?, dynamic> object) =>
    (object["type"] as String?) == "GeometryCollection"
        ? {
            "type": "FeatureCollection",
            "features": (object["geometries"] as List<Map<String?, dynamic>>)
                .map((o) => _feature(topology, o))
                .toList()
          }
        : _feature(topology, object);