whenOrNull<TResult extends Object?> method

  1. @optionalTypeArgs
TResult? whenOrNull<TResult extends Object?>({
  1. TResult? initial()?,
  2. TResult? loading()?,
  3. TResult? success(
    1. Todo todo
    )?,
  4. TResult? error(
    1. String? message
    )?,
})

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()?  initial,TResult? Function()?  loading,TResult? Function( Todo todo)?  success,TResult? Function( String? message)?  error,}) {final _that = this;
switch (_that) {
case _Initial() when initial != null:
return initial();case _Loading() when loading != null:
return loading();case _Success() when success != null:
return success(_that.todo);case _Error() when error != null:
return error(_that.message);case _:
  return null;

}
}