scoping_functions.dart

extension ScopingFunctions<T> on T {
  /// Calls the specified function [block] with `this` value
  /// as its argument and returns its result.
  R let<R>(R Function(T) block) => block(this as T);

  /// Calls the specified function [block] with `this` value
  /// as its argument and returns `this` value.
  T also(void Function(T) block) {
    block(this as T);
    return this as T;
  }
}

// Example usage
main() {
  Map<String, String> maybeNull;
  maybeNull = {'hello': 'world'};

  final bar = maybeNull?.also((absolutelyNotNull) {
        absolutelyNotNull.addAll({'mickey': 'mouse'});
      });

  print(bar); // {hello: world, mickey: mouse}

  final int nrOfKeys = bar?.let((mapNotNull) => mapNotNull.keys.length);
  
  print(nrOfKeys); // 2
}