when<TResult extends Object?> method

@optionalTypeArgs TResult when<TResult extends Object?>(TResult $default(num total, @JsonKey.new(name: 'discount_total') num discountTotal, num discount))

A switch-like method, using callbacks.

As opposed to map, this offers destructuring. It is equivalent to doing:

switch (sealedClass) {
  case Subclass(:final field):
    return ...;
  case Subclass2(:final field2):
    return ...;
}

Implementation

@optionalTypeArgs
TResult when<TResult extends Object?>(
  TResult Function(num total,
          @JsonKey(name: 'discount_total') num discountTotal, num discount)
      $default,
) {
  final _that = this;
  switch (_that) {
    case _IsibookReserveTotal():
      return $default(_that.total, _that.discountTotal, _that.discount);
  }
}