How can i send the Map Object in multipart request in flutter - flutter

Question

Here I am trying to send the Object Map in the multipart request but my request is going as a string, not in JSON format please suggest me to do correct request. Thanks in advance.
I have tried the multipart request but my request should be in correct form..
var getApiUrl = 'http://malik-env-test.ap-south-1.elasticbeanstalk.com/webapi/post/create';
Map userData = {
"creator": {
"creatorId": "298",
"createDate": "2018-12-21 20:44:45.8"
},
"info": "$campusInfo",
"title": "$eventName",
"postCampusId": "5642"
};
Uri uri = Uri.parse(getApiUrl);
http.MultipartRequest request = new http.MultipartRequest('POST', uri);
request.fields['creator'] = userData['creator'];
request.fields['info'] = '$campusInfo';
request.fields['title'] = '$eventName';
request.fields['postCampusId'] = '5642';
request.files.add(await http.MultipartFile.fromPath('image_file1', imagePath, contentType: new MediaType('application', 'x-tar')));
// var body = json.encode(request);
print(request);
http.StreamedResponse response = await request.send();
String jsonData = response.toString();
print(jsonData);ddd

Answer 1

Try:
request.fields['userData'] = json.encode(userData);
You need to find out from the API spec or server owner what field name to use for the json. I've assumed userData.
If you want control over the media type, encoding, etc, add it as a file like this:
request.files.add(
http.MultipartFile.fromBytes(
'the_form_field name',
utf8.encode(json.encode(userData)),
contentType: MediaType(
'application',
'json',
{'charset': 'utf-8'},
),
),
);

Answer 2

I think, the easiest way to add object fields is using brackets like this ;
request.fields['creator[creatorId]'] = '$creatorId';
request.fields['creator[createDate]'] = '$createDate';
request.fields['title'] = '$eventName';
request.fields['postCampusId'] = '5642';
So, for the fields inside another you need to put the object name first then add to fields name inside brackets.
this should work just fine.

Answer 3

var userData = json.encode({
"creator": {
"creatorId": "298",
"createDate": "2018-12-21 20:44:45.8"
},
"info": "$campusInfo",
"title": "$eventName",
"postCampusId": "5642"
});
var client = http.Client();
client
.post('https://'+ url ,
headers: {
'content-type': 'application/json',
},
body: userData )