在 http 调用中将对象转换为可编码对象失败

Question

我收到了来自 API 的响应，但出现了错误。 我在调用 topicpurchased() 时没有得到任何响应

Future<bool> topicpurchased(int topicid, String title) async {
  var map = new Map<String, dynamic>();
  map['topicid'] = topicid;
  map['title'] = title;
  var data = json.encode(map);
  print(data);
  var response = await http.post(Constants.ApiBaseUrl + '/topicpuchased',
      headers: headers, body: data);
  if (response.statusCode == 200) {
    print("topicpurchasede" + response.body);
    TrueOrFalse trueOrFalse = TrueOrFalse.fromJson(json.decode(response.body));
    if (trueOrFalse.status == "sucess") {
      print(" ????????????????????????????????");
      return true;
    } else {
      print("something went wrong" + trueOrFalse.status);
      return false;
    }
  } else {
    throw Exception('Failed');
  }
}

控制台报错如下

I/flutter (22130): topicpurchasede{"status":"sucess"}
I/flutter (22130): datamodel sucess
I/flutter (22130):  ????????????????????????????????
E/flutter (22130): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: Converting object to an encodable object failed: Instance of 'Future<String>'
E/flutter (22130): #0      _JsonStringifier.writeObject (dart:convert/json.dart:688:7)
E/flutter (22130): #1      _JsonStringifier.writeMap (dart:convert/json.dart:769:7)
E/flutter (22130): #2      _JsonStringifier.writeJsonValue (dart:convert/json.dart:724:21)
E/flutter (22130): #3      _JsonStringifier.writeObject (dart:convert/json.dart:679:9)
E/flutter (22130): #4      _JsonStringStringifier.printOn (dart:convert/json.dart:877:17)
E/flutter (22130): #5      _JsonStringStringifier.stringify (dart:convert/json.dart:862:5)
E/flutter (22130): #6      JsonEncoder.convert (dart:convert/json.dart:262:30)
E/flutter (22130): #7      JsonCodec.encode (dart:convert/json.dart:172:45)

提前致谢。

Answer 1

首先，您必须使用 await 调用函数，因为它是 Future：

例子：

bool response = await topicpurchased(topicid,title);

Future<bool> topicpurchased(int topicid, String title) async {
  var map = new Map<String, dynamic>();
  map['topicid'] = topicid;
  map['title'] = title;
  var data = json.encode(map);
  print(data);
  var response = await http.post(Constants.ApiBaseUrl + '/topicpuchased',
      headers: headers, body: data);
  if (response.statusCode == 200) {
    print("topicpurchasede" + response.body);
    //here could be the bug
    TrueOrFalse trueOrFalse = TrueOrFalse.fromJson(json.decode(response.body));
    if (trueOrFalse.status == "sucess") {
      print(" ????????");
      return true;
    } else {
      print("something went wrong" + trueOrFalse.status);
      return false;
    }
  } else {
    //second: here too you can send a bool return because you function has declare a 
    //bool response
    throw Exception('Failed');
  }
}

第三：错误似乎来自您的模型，您可以在此行注释并运行应用程序以查看错误是否来自那里