How can I filter a map / access the entries

Question

The Map interface doesn\'t seem to provide access to the entries as an iterable, nor does it expose a where method to filter entries. Am I missing something? Is there a simple w

Answer 1

Since Dart 2.0 Maps have an entries getter that returns an Iterable<MapEntry<K, V>> so you can do:

MapEntry theOne = map.entries.firstWhere((entry) {
        return entry.key.startsWith('foo');
      }, orElse: () => MapEntry(null, null));

Answer 2

Dart 2.0.0 added removeWhere which can be used to filter Map entities. Given your example, you could apply this as:

Map map;
final filteredMap = Map.from(map)..removeWhere((k, v) => !k.startsWith("foo"));

It's not the where method you asked for, but filtering Map entities is certainly doable this way.

Answer 3

You can use

library x;

void main(List<String> args) {
  Map map = {'key1': 'aölsjfd', 'key2': 'oiweuwrow', 'key11': 'oipoip', 'key13': 'werwr'};

  final filteredMap = new Map.fromIterable(
      map.keys.where((k) => k.startsWith('key1')), key: (k) => k, value: (k) => map[k]);

  filteredMap.forEach((k, v) => print('key: $k, value: $v'));
}