Here I am trying to send the Object Map in the multipart request but my request is going as a string, i need send the Object Map not String . but request .fields wants a String from me.

    "barberAddress":{
              "State":"test",
        "City":"test",
        "Street": "test",
        "location":{
            "lat":1.2,
            "lang":2.1
        }
     },

This is my post method

postFormDataBarber({
@required String endPoint,
File picB,barberName,BarberAddress barberAddress, }) async {
var url = Uri.parse('${BaseUrl.baseUrl}$endPoint');
var request = http.MultipartRequest("POST", url); 
request.fields["barberAddress"] = json.encode(barberAddress);// {"State":"aaa","City":"vvv","Street":"eeee","location":{"lat":null,"lang":null}}

request.files.add(picB);   
final data = await request.send();
return data;

}

This is my model and I want to add this model map object to the Mango database

    class BarberAddress {
    BarberAddress({
    @required this.state,
    @required this.city,
    @required this.street,
    this.location,
    });
   String state;
   String city;
   String street;
   BarberLocation location;
   factory BarberAddress.fromJson(Map<String, dynamic> json) => 
   BarberAddress(
   state: json["State"],
   city: json["City"],
   street: json["Street"],
   location: BarberLocation.fromJson(json["location"]),
    );
    class BarberLocation {
    BarberLocation({
    @required this.lat,
    @required this.lang,
    });
    double lat;
    double lang;
    factory BarberLocation.fromJson(Map<String, dynamic> json) => 
    BarberLocation(
    lat: json["lat"].toDouble(),
    lang: json["lang"].toDouble(),
    );
    Map<String, dynamic> toJson() => {
    "lat": lat,
    "lang": lang,
    };
    }


Solution 1: Ismail Omar

Flutter multipart request fields take only Map<String, String>. If you pass Map<String, dynamic> will arise error.

You need to encode your Map<String,dynamic> then covert to string.

if your server can decode this string you can apply my solution

THE SOLUTION FOR ME:

var data = {
      "State":"test",
      "City":"test",
      "Street": "test",
      "location":{
                "lat":1.2,
                "lang":2.1
      }
};

var header = {
  "Content-Type": 'multipart/form-data',
  "Accept": 'application/json'
};

Map<String, String> obj = {"barberAddress": json.encode(data).toString()};
var request = http.MultipartRequest("POST", Uri.parse("url here"))
  ..fields.addAll(obj)
  ..headers.addAll(header)
  ..files.addAll(files);

var streamResponse = await request.send();
var response = await http.Response.fromStream(streamResponse);
// Your result here

IN SEVER SIDE

LARAVEL:

$obj = json_decode($request["barberAddress"], true);
// Your code here

OR

$obj = json_decode($request->barberAddress, true);
// Your code here

IF IT IS HARD TO DECODE YOUR OBJECT ON SEVER USE

flutter dio package through this link : dio flutter package

I THINK MAY HELP SOMEONE