separatedBy method

Iterable<E> separatedBy(
  1. Builder<E> separator, {
  2. Builder<E>? before,
  3. Builder<E>? after,
})

Returns an Iterable where every element is separated by an element built by a separator builder. Optionally specified before and after builders can provide an element at the beginning or the end of the non-empty iterable.

For example:

final input = [1, 2, 3];
print(input.separatedBy(() => 0));  // [1, 0, 2, 0, 3]
print(input.separateBy(() => 0, before: () => -1));  // [-1, 1, 0, 2, 0, 3]
print(input.separateBy(() => 0, after: () => -1));  // [1, 0, 2, 0, 3, -1]

Implementation

Iterable<E> separatedBy(Builder<E> separator,
    {Builder<E>? before, Builder<E>? after}) sync* {
  var index = 0;
  for (final iterator = this.iterator; iterator.moveNext(); index++) {
    if (index == 0 && before != null) yield before();
    if (index > 0) yield separator();
    yield iterator.current;
  }
  if (index > 0 && after != null) yield after();
}