whenOrNull<TResult extends Object?> method

@optionalTypeArgs TResult? whenOrNull<TResult extends Object?>(TResult? $default(String? currencyFormat, String? currencyFormatSymbolISOCurrency, String? currencyCode, String? currencySymbol, String? currencyValue,)?)

A variant of when that fallback to returning null

It is equivalent to doing:

switch (sealedClass) {
  case Subclass(:final field):
    return ...;
  case _:
    return null;
}

Implementation

@optionalTypeArgs
TResult? whenOrNull<TResult extends Object?>(
  TResult? Function(
          String? currencyFormat,
          String? currencyFormatSymbolISOCurrency,
          String? currencyCode,
          String? currencySymbol,
          String? currencyValue)?
      $default,
) {
  final _that = this;
  switch (_that) {
    case _Amount() when $default != null:
      return $default(
          _that.currencyFormat,
          _that.currencyFormatSymbolISOCurrency,
          _that.currencyCode,
          _that.currencySymbol,
          _that.currencyValue);
    case _:
      return null;
  }
}