Control flow collections example https://dartpad.dev/55b1be6c3cda8e689ef0b6126032da64

control_flow_collections.dart

/// An example of operations you can do with control flow collections.
///
/// They make it very easy to do map, filter, and spread operations, all
/// while retaining the base class of [List<T>], [Set<T>], and [Map<K,V>]
void main() {
  final source = [1, 2, 3, null, 4, 5, null];

  /// List control flow, map & filter
  final myList = [
    for (var number in source)
      if (number != null)
        if (number.isEven)
          '$number is even'
        else if (number == 5)
          '$number is five'
        else
          '$number is odd',

    /// You can also spread the collection
    if (source.length.isOdd) ...['spread foo', 'spread bar']
  ];

  print(myList);

  /// Set control flow, map & filter
  final mySet = {
    for (var number in source)
      if (number != null)
        if (number.isEven)
          '$number is even'
        else if (number == 5)
          '$number is five'
        else
          '$number is odd',

    /// You can also spread the collection
    if (source.length.isOdd) ...{'spread foo', 'spread bar'}
  };

  print(mySet);

  /// Map control flow, map & filter
  final myMap = {
    for (var number in source)
      if (number != null)
        if (number.isEven)
          number: 'even'
        else if (number == 5)
          number: 'five'
        else
          number: 'odd',

    /// You can also spread the collection
    if (source.length.isOdd) ...{-1: 'spread foo', -2: 'spread bar'}
  };

  print(myMap);
}