Flutter HTTP POST request error in type cast

Question

My code is :

var header = {"cookie": db.getString("cookie")};
var body={"nonce":_nonce.nonce,"action":"GetTrafficList" ,"params":{"filters":{"credit":{"mode":"none"}}}};
var response = await post(Urls.traffics, headers: header,body:body);

The following error occurs when executing :

Restarted application in 4,619ms.
E/flutter (22004): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: type '_InternalLinkedHashMap<String, Map<String, Map<String, String>>>' is not a subtype of type 'String' in type cast
E/flutter (22004): #0      CastMap.forEach.<anonymous closure> (dart:_internal/cast.dart:288:25)
E/flutter (22004): #1      _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:379:8)
E/flutter (22004): #2      CastMap.forEach (dart:_internal/cast.dart:287:13)
E/flutter (22004): #3      mapToQuery (package:http/src/utils.dart:17:7)
E/flutter (22004): #4      Request.bodyFields= (package:http/src/request.dart:137:12)
E/flutter (22004): #5      BaseClient._sendUnstreamed (package:http/src/base_client.dart:170:17)
E/flutter (22004): #6      BaseClient.post (package:http/src/base_client.dart:58:7)
E/flutter (22004): #7      post.<anonymous closure> (package:http/http.dart:70:16)
E/flutter (22004): #8      _withClient (package:http/http.dart:166:20)
E/flutter (22004): #9      post (package:http/http.dart:69:5)
E/flutter (22004): #10     Traffic.GetTraffic (package:adsl_tci/Traffic.dart:23:26)
E/flutter (22004): <asynchronous suspension>

I think the problem is with the body content :

mohammad mobasher · Accepted Answer · 2021-09-01 18:52:42Z

you have to mention about you'r request provider http or dio. hopefully i have some example in both

HTTP

Future<NetworkResponse> post(String url, {Map<String, dynamic> body}) async {
    var token = "AccessToken";
    return await http.post(_baseUrl + url,
        headers: {
          "Authorization": 'Bearer ' + token,
          "Accept": "application/json"
        },
        body: body);

}

as you can see we have to send endpoint url and body to this function. for creating a map of data you can create a function like this

Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['text'] = text;
    return data;
}

DIO

Dio getBaseDio() {
var token = "AccessToken";
Dio dio = Dio(BaseOptions(baseUrl: MPref.getString("ApiAddress"),

    headers: {
      "Authorization": "Bearer $token",
      "Accept": "application/json",
    }));


return dio;

}

Future<Response> post(String url, {Map<String, dynamic> body}) async {
    return await getBaseDio().post(url, data: FormData.fromMap(body));
});

}

I hope I was able to help.

Sebastian · Accepted Answer · 2020-02-25 15:13:11Z

0

You need to convert your body to json. Try encoding your body

var response = await post(Urls.traffics, headers: header, body: json.encode(body));

You will need to import 'dart:convert'; at the top of your file

answered Feb 25, 2020 at 15:13

Sebastian

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2 Comments

Sebastian Over a year ago

What you mean by that? The body parameter of http.post() needs a String value, you are not providing a String value in your code

Alireza 271 Over a year ago

when var body={"nonce":_nonce.nonce,"action":"GetTrafficList" } not problem but when change to var body={"nonce":_nonce.nonce,"action":"GetTrafficList" ,"params":{"filters":{"credit":{"mode":"none"}}}} An error occurs

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