如何从Dart http调用返回json /如何完全消耗流？ [英] How to return a json from a Dart http call / How to consume a stream entirely?

问题描述

这是我的代码，应该返回一个json。我从这里 https://github.com/flutter/flutter/issues/15110

Here's my code that should return a json. I adapted this code from here https://github.com/flutter/flutter/issues/15110

  Stream _defaultReturn(HttpClientResponse httpClientResponse) {
    Stream response = httpClientResponse.
                      transform(utf8.decoder).
                      transform(json.decoder).
                      asyncMap((json) => jsonDecode(json));
    return response;
  }

  Future<dynamic> get(String endpoint) async {
    HttpClientRequest httpClientRequest =
        await httpClient.getUrl(Uri.parse(_url + endpoint));
    _addCookies(httpClientRequest);
    final HttpClientResponse httpClientResponse =
        await httpClientRequest.close();
    return _defaultReturn(httpClientResponse);
  }

我将返回类型为 Stream 放入 _defaultReturn ，因为intellisense告诉我，巨大的东西使我返回了 Stream 。我实际上想接收一个json（应该是地图）。我想我会消耗或订阅此流以获得有用的东西。但是，我认为parsin json作为流不是有用的。解析之前，我不需要整个json吗？

I've put a return type of Stream into _defaultReturn because intellisense told me that giant thing returned me a Stream. I would actually want to receive a json (which should be a map). I think I migth consume or subscribe to this stream to get something useful. However, I don't see parsin json as stream as being useful. Don't I need the entire json before parsing? Shouldn't I simply accumulate everything into a String and then simply call jsonDecode?

哪个是从http调用返回json的最有效方法？以及如何做？

Which is the most efficient way of returning a json from an http call? And how to do it?

推荐答案

json.decoder 将侦听源代码流，并且始终将其内容转换为一个 对象，因此您只需将其与流的<$ c $一起返回即可c> .first ：

json.decoder will listen source stream and always transform its content to just one Object, so you can just return it with stream's .first:

Future<Object> get(String endpoint) async {
  var httpClientRequest = await httpClient.getUrl(Uri.parse(_url + endpoint));
  _addCookies(httpClientRequest);
  final httpClientResponse = await httpClientRequest.close();
  return httpClientResponse
           .transform(utf8.decoder)
           .transform(json.decoder)
           .first;
}

然后您可以像这样使用它：

Then you can use it like this:

var jsonObject = await myHttpClient.get(myEndpoint);

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