Flutter JSON Array Parsing getting error : Exception: type '(dynamic) => xxx is not a subtype of type '(Map<String, dynamic>) => List<xxx>' of 'f'

Question

Sorry if It's repeated the question but I didn't found a solution.

Error:

Exception: type '(dynamic) => PostalModel' is not a subtype of type '(Map<String, dynamic>) => List' of 'f'

What I have done:

Calling API:

Future<PostalModel> fetchPhotos(http.Client client) async {
   final response =
    await client.get('https://api.postalpincode.in/pincode/364710');

   // Use the compute function to run parsePhotos in a separate isolate.
   return compute(parsePostalPincode, response.body);
}

parsing JSON:

 // A function that converts a response body into a List.
 PostalModel parsePostalPincode(String responseBody) {
   print(responseBody);
   final parsed = jsonDecode(responseBody).cast<Map<String, dynamic>>();
   print('Parsed : $parsed'); //Getting Log OUTPUT
   PostalModel postalModel = parsed.map<List<PostalModel>>((json) => PostalModel.fromJson(json));
   print('Postal Model : $postalModel'); //Getting Log OUTPUT
   return postalModel;
 }

Binding Data in body:

body: FutureBuilder<PostalModel>(
  future: fetchPhotos(http.Client()),
  builder: (context, snapshot) {
    print('snapshot $snapshot'); // Getting Error Here
    // "AsyncSnapshot<PostalModel>(ConnectionState.done, null, Exception: type '(dynamic) => PostalModel' is not a subtype of type '(Map<String, dynamic>) => List<PostalModel>' of 'f')"
    if (snapshot.hasError) print(snapshot.error);

    return snapshot.hasData
       ? PostOfficeList(postOfficeList: snapshot.data.postOffice)
       : Center(child: CircularProgressIndicator());
  },
),

You can check JSON from API Link and I have created a Model class from here.

Pratik Butani · Accepted Answer · 2020-11-05 06:27:18Z

0

And finally, I got succeed with the following solution:

// A function that converts a response body into a List.
PostalModel parsePostalPincode(String responseBody) {
  final parsed = jsonDecode(responseBody).cast<Map<String, dynamic>>();
  print('Parsed : $parsed[0]'); 
  PostalModel postalModel = PostalModel.fromJson(parsed[0]);
  print('Postal Model : $postalModel');
  return postalModel;
}

Flutter is so crazy for a newbie. :P

answered Nov 5, 2020 at 6:27

Pratik Butani

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