decode static method Null safety

Implementation

static FillLayer decode(String properties) {
  var map = json.decode(properties);
  if (map["layout"] == null) {
    map["layout"] = {};
  }
  if (map["paint"] == null) {
    map["paint"] = {};
  }
  return FillLayer(
    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"])),
    fillSortKey: map["layout"]["fill-sort-key"]?.toDouble(),
    fillAntialias: map["paint"]["fill-antialias"],
    fillColor: (map["paint"]["fill-color"] as List?)?.toRGBAInt(),
    fillOpacity: map["paint"]["fill-opacity"]?.toDouble(),
    fillOutlineColor:
        (map["paint"]["fill-outline-color"] as List?)?.toRGBAInt(),
    fillPattern: map["paint"]["fill-pattern"],
    fillTranslate: (map["paint"]["fill-translate"] as List?)
        ?.map<double?>((e) => e.toDouble())
        .toList(),
    fillTranslateAnchor: map["paint"]["fill-translate-anchor"] == null
        ? null
        : FillTranslateAnchor.values.firstWhere((e) => e
            .toString()
            .split('.')
            .last
            .toLowerCase()
            .contains(map["paint"]["fill-translate-anchor"])),
  );
}