whenOrNull<TResult extends Object?> method

  1. @optionalTypeArgs
TResult? whenOrNull<TResult extends Object?>(
  1. TResult? $default(
    1. bool isRequired,
    2. bool isNamed,
    3. String name,
    4. bool isDeprecated,
    5. bool isExperimental,
    6. String typeName,
    7. String? typeFullLibraryName,
    8. String relativePath,
    )?
)

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(
          bool isRequired,
          bool isNamed,
          String name,
          bool isDeprecated,
          bool isExperimental,
          String typeName,
          String? typeFullLibraryName,
          String relativePath)?
      $default,
) {
  final _that = this;
  switch (_that) {
    case _ExecutableParameterDeclaration() when $default != null:
      return $default(
          _that.isRequired,
          _that.isNamed,
          _that.name,
          _that.isDeprecated,
          _that.isExperimental,
          _that.typeName,
          _that.typeFullLibraryName,
          _that.relativePath);
    case _:
      return null;
  }
}