Flutter multipart/form-data send list of items

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

You have to use a for loop and assign indexes for list

Ravindra
– Ravindra

2021-01-10 13:28:15 +00:00
Commented Jan 10, 2021 at 13:28 — Ravindra
– Ravindra, Commented Jan 10, 2021 at 13:28

Dharman · Accepted Answer · 2021-02-22 15:36:20Z

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

edited Feb 22, 2021 at 15:36

Dharman♦

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answered Feb 22, 2021 at 15:30

AshishB

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1 Comment

rminaj Over a year ago

This looks weird, but it works

olayemii · Accepted Answer · 2021-09-15 07:37:39Z

2

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()));
});

answered Sep 15, 2021 at 7:37

olayemii

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