在 BLoC 模式中传递参数 Flutter(Stream Controller)

Posted 2023-02-23

【中文标题】在 BLoC 模式中传递参数 Flutter(Stream Controller)

【英文标题】：Pass parameter in BLoC pattern Flutter(Stream Controller)

【发布时间】：2022-01-15 20:21:44

【问题描述】：

我是 Flutter 的新手，不确定这是否是正确的方法。我正在按照 YouTube 教程使用 TMDB API 创建电影应用程序，并尝试将 category.dart（下面的评论）中的“genreId”传递给 MovieBloc.dart。是否可以发送“genreId”？如果是，我该如何通过？如果没有，最好的方法是什么？ 谢谢

category.dart

final movieBloc = MovieBloc();

setState(() 
          selectedGenre = genre.id;
          movieBloc.eventSink.add(MovieControlAction.byGenre); // send genreId through here??
);

movie_bloc.dart

import 'dart:async';

import 'package:flutter_api/Model/movie.dart';
import 'package:flutter_api/Service/api_service.dart';

enum MovieControlAction  fetch, delete, byGenre, 

class MovieBloc 
  final service = ApiService();
  final _stateStreamController = StreamController<List<Movie>>();

  StreamSink<List<Movie>> get _movieSink => _stateStreamController.sink;
  Stream<List<Movie>> get movieStream => _stateStreamController.stream;

  final _eventStreamController = StreamController<MovieControlAction>();
  StreamSink<MovieControlAction> get eventSink =>
      _eventStreamController.sink; //input
  Stream<MovieControlAction> get _eventStream =>
      _eventStreamController.stream; //output

  MovieBloc() 
    _eventStream.listen((event) async 
      if (event == MovieControlAction.fetch) 
        try 
          var movies = await service.getNowPlayingMovie();
          if (movies != null) 
            _movieSink.add(movies);
           else 
            _movieSink.addError('Null');
          
         on Exception catch (e) 
          print(e);
          _movieSink.addError('Something went wrong');
        
       else if (event == MovieControlAction.byGenre) 
        var moviesByGenre = await service.getMovieByGenre(genreId);
        if (moviesByGenre != null) 
          _movieSink.add(moviesByGenre);
         else 
          _movieSink.addError('Null');
        
      
    );
  
  void dispose() 
    _stateStreamController.close();
    _eventStreamController.close();
  

【参考方案1】：

您可以将其传递给 MovieBloc，如下所示：

final movieBloc = MovieBloc(genreId: genre.id);

然后在 MovieBloc 类中创建一个构造函数：

class MovieBloc 
   final String genreId; // String, int, whatever type it is

   MovieBloc(
    required this.genreId,
   );

如果你想使用真正的 Bloc，你应该像这样扩展 MovieBloc：

class MovieBloc extends Bloc<MovieEvent, MovieState> 

目前看起来您并没有使用实际的 Bloc 模式。请查看official Bloc documentation。我保证 - 它非常有用。