aggregate<R> method

Map<K, R> aggregate<R>(AggregateOperation<T, K, R> operation)

For each group the operation is applied to the elements of that group sequentially.

The previous accumulated value is passed and the current element. The result per group is stored in a new map.

The key for each element is provided by the [](T element) operator.

final numbers = [3, 4, 5, 6, 7, 8, 9];

final aggregated = numbers
    .groupingBy((value) => value % 3)
    .aggregate((key, accumulator, element, first) {
  return first ? '$key:$element' : '$accumulator-$element';
});

print(aggregated.values); // (0:3-6-9, 1:4-7, 2:5-8)

Implementation

Map<K, R> aggregate<R>(AggregateOperation<T, K, R> operation) {
  return aggregateTo({}, operation);
}