mapOrNull<TResult extends Object?> method

  1. @optionalTypeArgs
TResult? mapOrNull<TResult extends Object?>({
  1. TResult? user(
    1. MessageOriginUser value
    )?,
  2. TResult? hiddenUser(
    1. MessageOriginHiddenUser value
    )?,
  3. TResult? chat(
    1. MessageOriginChat value
    )?,
  4. TResult? channel(
    1. MessageOriginChannel value
    )?,
})

A variant of map that fallback to returning null.

It is equivalent to doing:

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

Implementation

@optionalTypeArgs
TResult? mapOrNull<TResult extends Object?>({
  TResult? Function(MessageOriginUser value)? user,
  TResult? Function(MessageOriginHiddenUser value)? hiddenUser,
  TResult? Function(MessageOriginChat value)? chat,
  TResult? Function(MessageOriginChannel value)? channel,
}) {
  final _that = this;
  switch (_that) {
    case MessageOriginUser() when user != null:
      return user(_that);
    case MessageOriginHiddenUser() when hiddenUser != null:
      return hiddenUser(_that);
    case MessageOriginChat() when chat != null:
      return chat(_that);
    case MessageOriginChannel() when channel != null:
      return channel(_that);
    case _:
      return null;
  }
}