decode static method Null safety

Implementation

static FillExtrusionLayer decode(String properties) {
  var map = json.decode(properties);
  if (map["layout"] == null) {
    map["layout"] = {};
  }
  if (map["paint"] == null) {
    map["paint"] = {};
  }
  return FillExtrusionLayer(
    id: map["id"],
    sourceId: map["source"],
    sourceLayer: map["source-layer"],
    minZoom: map["minzoom"]?.toDouble(),
    maxZoom: map["maxzoom"]?.toDouble(),
    visibility: map["layout"]["visibility"] == null
        ? Visibility.VISIBLE
        : Visibility.values.firstWhere((e) => e
            .toString()
            .split('.')
            .last
            .toLowerCase()
            .contains(map["layout"]["visibility"])),
    fillExtrusionBase: map["paint"]["fill-extrusion-base"] is num?
        ? (map["paint"]["fill-extrusion-base"] as num?)?.toDouble()
        : null,
    fillExtrusionColor:
        (map["paint"]["fill-extrusion-color"] as List?)?.toRGBAInt(),
    fillExtrusionHeight: map["paint"]["fill-extrusion-height"] is num?
        ? (map["paint"]["fill-extrusion-height"] as num?)?.toDouble()
        : null,
    fillExtrusionOpacity: map["paint"]["fill-extrusion-opacity"] is num?
        ? (map["paint"]["fill-extrusion-opacity"] as num?)?.toDouble()
        : null,
    fillExtrusionPattern: map["paint"]["fill-extrusion-pattern"] is String?
        ? map["paint"]["fill-extrusion-pattern"] as String?
        : null,
    fillExtrusionTranslate:
        (map["paint"]["fill-extrusion-translate"] as List?)
            ?.map<double?>((e) => e.toDouble())
            .toList(),
    fillExtrusionTranslateAnchor:
        map["paint"]["fill-extrusion-translate-anchor"] == null
            ? null
            : FillExtrusionTranslateAnchor.values.firstWhere((e) => e
                .toString()
                .split('.')
                .last
                .toLowerCase()
                .contains(map["paint"]["fill-extrusion-translate-anchor"])),
    fillExtrusionVerticalGradient:
        map["paint"]["fill-extrusion-vertical-gradient"] is bool?
            ? map["paint"]["fill-extrusion-vertical-gradient"] as bool?
            : null,
  );
}