read_screen.dart

class ReadScreen extends StatefulWidget {
  final String bookId;

  final LibraryService libraryService;

  const ReadScreen({
    Key? key,
    required this.bookId,
    this.libraryService = const LibraryService(),
  }) : super(key: key);

  @override
  State<StatefulWidget> createState() => _ReadScreenState();
}

class _ReadScreenState extends State<ReadScreen> {
  @override
  void initState() {
    super.initState();

    _bookResult = _fetchBook();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: _buildFutureBuilder(context),
    );
  }

  FutureBuilder _buildFutureBuilder(BuildContext context) {
    return FutureBuilder(
      future: _bookResult,
      builder: (context, snapshot) => _buildContent(
        context,
        snapshot.data,
      ),
    );
  }

  Widget _buildContent(BuildContext, data) {
    return Text(data.value)
  }

  Future<String> _fetchBook() async {
    String bookContent =
        await widget.libraryService.getBook(bookId);
    return Result(value: bookContent);
  }
}