parseOn method

@override Result<R> parseOn(Context context)

Primitive method doing the actual parsing.

The method is overridden in concrete subclasses to implement the parser specific logic. The methods takes a parse context and returns the resulting context, which is either a Success or Failure context.

Implementation

@override
Result<R> parseOn(Context context) {
  final result = delegate.parseOn(context);
  if (result.isSuccess) {
    final value = result.value;
    final picked = value[index < 0 ? value.length + index : index];
    return result.success(picked);
  } else {
    return result.failure(result.message);
  }
}