GeoJSONMultiPolygon.fromMap constructor

GeoJSONMultiPolygon.fromMap(Map<String, dynamic> map)

Constructs a GeoJSONMultiPolygon from a map.

The map must contain a 'type' key with the value 'MultiPolygon', and a 'coordinates' key with the value being a list of Polygon coordinate arrays.

Implementation

factory GeoJSONMultiPolygon.fromMap(Map<String, dynamic> map) {
  assert(map.containsKey('type'), 'There MUST be contains key `type`');
  assert(['MultiPolygon'].contains(map['type']), 'Invalid type');
  assert(map.containsKey('coordinates'),
      'There MUST be contains key `coordinates`');
  assert(map['coordinates'] is List,
      'There MUST be array of Polygon coordinate arrays.');
  final lllll = map['coordinates'];
  final coords = <List<List<List<double>>>>[];
  lllll.forEach((llll) {
    final polygon = <List<List<double>>>[];
    assert(llll is List, 'There MUST be List');
    llll.forEach((lll) {
      assert(lll is List, 'There MUST be List');
      final rings = <List<double>>[];
      lll.forEach((ll) {
        assert(ll is List, 'There MUST be List');
        assert((ll as List).length > 1, 'There MUST be two or more element');
        final pos = ll.map((e) => e.toDouble()).cast<double>().toList();
        rings.add(pos);
      });
      polygon.add(rings);
    });
    coords.add(polygon);
  });
  return GeoJSONMultiPolygon(coords);
}