Invalid argument(s): Illegal argument in isolate message : (object is a closure - Function 'createDataList':.)

Question

I tried to fetch data from the internet with moviedb API, I followed the tutorial at https://flutter.io/cookbook/networking/fetch-data/

but I'm getting the below error.

Invalid argument(s): Illegal argument in isolate message : (object is a closure - Function 'createDataList':.)

This my code

Future<List<DataModel>> fetchData() async{      final response = await http.get("https://api.themoviedb.org/3/movie/now_playing?api_key=d81172160acd9daaf6e477f2b306e423&language=en-US");        if(response.statusCode == 200){          return compute(createDataList,response.body.toString());      }    }      List<DataModel> createDataList(String responFroJson) {      final parse  = json.decode(responFroJson).cast<Map<String, dynamic>>();        return parse.map<DataModel> ((json) => DataModel.fromtJson(json)).toList();    }

Screenshot of the error message

Answer 1

compute can only take a top-level function, but not instance or static methods.

Top-level functions are functions declared not inside a class and not inside another function

List<DataModel> createDataList(String responFroJson) { ... }  class SomeClass { ... } 

should fix it.

https://docs.flutter.io/flutter/foundation/compute.html

R is the type of the value returned. The callback argument must be a top-level function, not a closure or an instance or static method of a class.

Answer 2

As per today (2020. Aug) the compute is working fine with static methods. For me, the issue was that I was trying to return a http.Response object from the compute() methods.

What I did is I've created a simplified version of this class, containing what I need:

class SimpleHttpResponse {   String body;   int statusCode;   Map<String, String> headers; } 

Then I've updated the original method from this:

static Future<http.Response> _executePostRequest(EsBridge bridge) async {     return await http.post(Settings.bridgeUrl, body: bridge.toEncryptedMessage()); }   

to this:

static Future<SimpleHttpResponse> _executePostRequest(EsBridge bridge) async {     http.Response result = await http.post(Settings.bridgeUrl, body: bridge.toEncryptedMessage());     if (result == null) {       return null;     }      SimpleHttpResponse shr = new SimpleHttpResponse();     shr.body = result.body;     shr.headers = result.headers;     shr.statusCode = result.statusCode;      return shr; } 

Worked like charm after this change. Hope this helps somebody ranning into similar problem.