aggregate method

T aggregate(T aggregator(T aggregate, T select))

Aggregates the iterable into a single value.

Aggregates the source iterable by applying the aggregator function to each value in the collection in the order they appear. The result is a single value that is the result of the aggregation.

The aggregator function offers two parameters - the accumulator and the value. In each iteration, the accumulator represents the running result of the aggregation and the value represents the current element to process. The function should return what the next value of the aggregation should be, and that value will become the accumulator on the next iteration. Once the aggregation is complete, the last value to be returned is considered the result of the aggregation process.

If this method is called on an empty iterable, a StateError is thrown.

Example:

void main() {
  final list = [0, 1, 2, 3, 4];
  final result = list.aggregate(0, (a, b) => a + b);

  // Result: 10
}

Implementation

T aggregate(
  T Function(T aggregate, T select) aggregator,
) {
  final iterator = this.iterator;
  if (!iterator.moveNext()) {
    throw StateError('Cannot call "aggregate" on an empty iterable.');
  }

  var result = iterator.current;

  while (iterator.moveNext()) {
    result = aggregator(result, iterator.current);
  }

  return result;
}