Flutter multipart/form-data send list of items - arrays

Question

My using package http
I have this method in my app to send post request with files. In my case I send files and also fields with dynamic values. I tried send List<String> but server (backend) return me error with message:
The seedlings field must be an array.
Example seedlings list value:
List<String> seedlings = ['Apple', 'Banana'];
Code:
Future post(String path, data) async {
await _getToken();
var url = '${ApiConstants.BASE_URL}$path';
var uri = Uri.parse(url);
var request = MultipartRequest('POST', uri);
data.forEach((key, item) async {
if (item == null) return null;
if (item is File) {
request.files.add(await MultipartFile.fromPath(
'file',
item.path,
));
} else {
request.fields[key] = item is num
? item.toString()
: item is List
? item.toString()
: item;
}
});
request.headers['Content-type'] = 'application/json';
request.headers['Accept'] = 'application/json';
var response = await request.send();
}
In my case all fields sent to server except fields with list of values like array

Answer 1

This might be old, but you can easily do this by adding the array items into a form data array
final FormData formData = FormData({});
// Add all normal string request body data
formData.fields.add(MapEntry("name", "Olayemii"));
formData.fields.add(MapEntry("age", 99));
// Add all files request body data
formData.files.add(MapEntry("profile_photo", file));
// Add the array item
List<String> seedlings = ['Apple', 'Banana'];
seedlings.forEach((element) {
formData.fields.add(MapEntry("seedlings[]", element.toString()));
});

Answer 2

I have found an answer for this which I have posted in another similar question. I'll just put the code snippet here.
final request = http.MultipartRequest('Post', uri);
List<String> ManageTagModel = ['xx', 'yy', 'zz'];
for (String item in ManageTagModel) {
request.files.add(http.MultipartFile.fromString('manage_tag_model', item));
}
Basically you have to add the list as files with fromString() method.
Find the original answer here-
https://stackoverflow.com/a/66318541/7337717