Flutter Firebase Cloud function can not be called

Question

I am getting an error whilst using Firebase Cloud Functions when I try to call a callable function from Flutter.

flutter: caught generic exception
flutter: PlatformException(functionsError, Firebase function failed with exception., {message: NOT FOUND, code: NOT_FOUND})

Here is how I try to call the cloud function with using cloud_functions: ^0.4.2+3

import 'package:cloud_functions/cloud_functions.dart';
      _check(String id) async {
        HttpsCallable callable = CloudFunctions.instance
            .getHttpsCallable(functionName: 'checkUserFavorites');
        try {
          final HttpsCallableResult result = await callable.call(
            <String, dynamic>{
              'id': id,
            },
          );
          print(result.data);
        } on CloudFunctionsException catch (e) {
          print('caught firebase functions exception');
          print(e.code);
          print(e.message);
          print(e.details);
        } catch (e) {
          print('caught generic exception');
          print(e);
        }
      }

Answer 1

I have experienced similar issues, and with few days of debugging and experimenting I found the solution only after studying the source code of Cloud Functions Plugin for Flutter.

When you deploy Firebase Cloud function, you can choose any region of preference (closer to your application the better). For example

// using DigitalOcean spaces
exports.generateCloudImageUrl = functions
    .region('europe-west3')
    .https.onCall((reqData, context) => {
...
}

When you want to call this function from Flutter app, you must specify the region, otherwise all goes to us-central1 which is default. See example code on how to use a function deployed in a specific region

final HttpsCallable generateCloudImageUrl = new CloudFunctions(region: "europe-west3")
      .getHttpsCallable(functionName: 'generateCloudImageUrl');

// NB! if you initialize with 'CloudFunctions.instance' then this uses 'us-central1' as default region! 

see cloud_function source for init.

Update, as of recent release, you can initialize as below;

FirebaseFunctions.instanceFor(region: "europe-west3").httpsCallable(
            "generateCloudImageUrl",
            options:
                HttpsCallableOptions(timeout: const Duration(seconds: 30)));