我无法创建其中包含另一张地图的地图

Question

我正在尝试创建一个注册模型并将其发送到我的 API，但“位置”密钥有另一个 map/jsonobject，其中包含“类型”：“点”和“坐标": [double, double].

最终的 json 对象应该看起来像这样

{
    "name": "Arsh Bansal",
    "email": "ab@yahoo.com",
    "password": "123456789",
    "birthday": "06-21-2000",
    "gender": "Male",
    "location": {
        "type": "Point", 
        "coordinates": [13.0987, 88.403]
    },
    "phone_number": "123456789"
}

网络助手代码如下：

import 'package:http/http.dart' as http;
import 'dart:convert';

class NetworkHelper {

  NetworkHelper(this.url);
  NetworkHelper.withHeader(this.url, this.headers);

  final String url;
  Map<String, String> headers;

  Future getData() async {

    http.Response response = await http.get(url);

    if(response.statusCode == 200) {
      String data = response.body;

      return jsonDecode(data);
    } else {
      String error = response.body;

    }
  }

  Future<http.Response> postData(Map body) async {

    http.Response response = await http.post(url, headers: headers, body: body);
    return response;

  }

}

但是我得到以下错误

我得到的错误是： 未处理的异常：类型“_InternalLinkedHashMap”不是类型 cast

中类型 'String' 的子类型

#0      CastMap.forEach.<anonymous closure> (dart:_internal/cast.dart:288:25)
#1      _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:379:8)
#2      CastMap.forEach (dart:_internal/cast.dart:287:13)
#3      mapToQuery (package:http/src/utils.dart:17:7)
#4      Request.bodyFields= (package:http/src/request.dart:137:12)
#5      BaseClient._sendUnstreamed (package:http/src/base_client.dart:170:17)
#6      BaseClient.post (package:http/src/base_client.dart:58:7)
#7      post.<anonymous closure> (package:http/http.dart:70:16)
#8      _withClient (package:http/http.dart:166:20)
#9      post (package:http/http.dart:69:5)
#10     NetworkHelper.postData (package:clubinn/services/network_helper.dart:28:36)
#11     Models.createUser (package:clubinn/models/models.dart:72:50)
#12     _SignUpPageState.build.<anonymous closure> (package:clubinn/sc<…>

Answer 1

您的问题是 http.post 和 body 参数的使用。如果您阅读文档，您会看到它被描述为：

body sets the body of the request. It can be a String, a List or a Map. If it's a String, it's encoded using encoding and used as the body of the request. The content-type of the request will default to "text/plain".

...

If body is a Map, it's encoded as form fields using encoding. The content-type of the request will be set to "application/x-www-form-urlencoded"; this cannot be overridden.

https://pub.dev/documentation/http/latest/http/post.html

您的输入 body 来自以下代码：

    Map<String, dynamic> body = {
      "name": name,
      "email": email,
      "password": password,
      "birthday": DOB,
      "gender": gender,
      "location": location.toJson(),
      "phone_number": mobile
    };

类型甚至不接近 Map<String, String> 因为例如位置被赋予 Map<String, dynamic> 作为值：

  Map<String,dynamic> toJson() => {
    "type": type,
    "coordinates": List<double>.from(coordinates.map((x) => x)),
  };

此外，我认为您一开始就不想给 body 地图。正如您在前面提到的文档中看到的那样，地图是 "encoded as form fields using encoding"。您真正想要的是将地图解析为 JSON 字符串并将该字符串作为正文提供给 http.post.

所以它应该是这样的：

http.Response response = await http.post(url, headers: headers, body: json.encode(body));

我无法创建其中包含另一张地图的地图

I am unable to create a map that has another map inside it

maps

json

http

dart

flutter