LateError (LateInitializationError: Field 'customTypeSchemas' has not been initialized.) Amplify Plugins Error

Question

I am trying to connect Amplify Api to my project and keep getting an error that reads LateError (LateInitializationError: Field 'customTypeSchemas' has not been initialized.) (Screenshot of the error is provided after the code snippet) which I take to mean that in the code that Amplify provided me there is a line somewhere that has late prefix for customTypeSchemas Field, which I can't find.

This is where I am initializing Amplify.

@override
void initState() {
  super.initState();
  _configureAmplify();
}

void _configureAmplify() async {
  if (!Amplify.isConfigured) {
    await Amplify.addPlugins([
      AmplifyDataStore(modelProvider: ModelProvider.instance),
      AmplifyAPI(),
    ]);

    try {
      await Amplify.configure(amplifyconfig);
    } catch (e) {
      print(e.toString());
    }
  }
}

Screenshot of the error

Here is my pubspec.yaml dependencies

dependencies:
  amplify_api: ^0.3.2
  amplify_datastore: ^0.3.2
  amplify_flutter: ^0.3.2
  bloc: ^8.0.2
  cupertino_icons: ^1.0.2
  flutter:
    sdk: flutter
  flutter_bloc: ^8.0.1

This is what's in the ModelProvider.dart that Amplify downloaded.

/*
* Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
*  http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file is distributed
* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
* express or implied. See the License for the specific language governing
* permissions and limitations under the License.
*/

// ignore_for_file: public_member_api_docs

import 'package:amplify_datastore_plugin_interface/amplify_datastore_plugin_interface.dart';

import 'Todo.dart';

export 'Todo.dart';

class ModelProvider extends ModelProviderInterface {
  @override
  String version = "d960b875068d46ff04d68879d96cc042";
  @override
  List<ModelSchema> modelSchemas = [Todo.schema];
  static final ModelProvider _instance = ModelProvider();

  static ModelProvider get instance => _instance;

  @override
  ModelType getModelTypeByModelName(String modelName) {
    switch (modelName) {
      case "Todo":
        {
          return Todo.classType;
        }
      default:
        {
          throw Exception("Failed to find model in model provider for model name: " + modelName);
        }
    }
  }
}

I did accidentally installed amplify_core: ^0.3.2, which I remove and ran flutter clean and, in ios folder, pod cache clean --all.

Steps to reproduce the problem:

1. Create flutter project
2. Add Amplify to your project
3. Add Database plugin
4. Add Api to your project
5. Try adding api plugin and run the app in iOS Simulator.

I am relatively new to programming and StackOverflow, so please excuse any mistakes I may have made in this post. Let me know if you need more info or you want to try something out.

Thanks in advance.

Answer 1

_configureAmplify is a future method, use FutureBuilder. You can also make it nullable and do a null check while using the model.

You can check When should I use a FutureBuilder?

Example code: check above link.

FutureBuilder(
    future: _configureAmplify(), // async work
    builder: (BuildContext context, snapshot) {
       switch (snapshot.connectionState) {
         case ConnectionState.waiting: return Text('Loading....');
         default:
           if (snapshot.hasError)
              return Text('Error: ${snapshot.error}');
           else
          return Text('Result:}');
        }
      },
    )

Answer 2

I recently observed that error after upgrading to flutter 2.10

I was able to fix it by adding the below override method to my model provider class

  @override
    List<ModelSchema> customTypeSchemas = [];

After adding that, your model should look like the one below

   /*
* Copyright 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
*  http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file is distributed
* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
* express or implied. See the License for the specific language governing
* permissions and limitations under the License.
*/

// NOTE: This file is generated and may not follow lint rules defined in your app
// Generated files can be excluded from analysis in analysis_options.yaml
// For more info, see: https://dart.dev/guides/language/analysis-options#excluding-code-from-analysis

// ignore_for_file: public_member_api_docs, file_names, unnecessary_new, prefer_if_null_operators, prefer_const_constructors, slash_for_doc_comments, annotate_overrides, non_constant_identifier_names, unnecessary_string_interpolations, prefer_adjacent_string_concatenation, unnecessary_const, dead_code

import 'package:amplify_datastore_plugin_interface/amplify_datastore_plugin_interface.dart';
import 'Todo.dart';

export 'Todo.dart';

class ModelProvider implements ModelProviderInterface {
  @override
  String version = "d960b875068d46ff04d68879d96cc042";
  @override
  List<ModelSchema> modelSchemas = [Todo.schema];
  static final ModelProvider _instance = ModelProvider();

  static ModelProvider get instance => _instance;

  ModelType getModelTypeByModelName(String modelName) {
    switch (modelName) {
      case "Todo":
        {
          return Todo.classType;
        }
        break;
      default:
        {
          throw Exception(
              "Failed to find model in model provider for model name: " +
                  modelName);
        }
    }
  }

  @override
  List<ModelSchema> customTypeSchemas = [];
}

Answer 3

You could try his

@override
List<ModelSchema> customTypeSchemas = [];

Make sure you initialize an empty list in your ModelProviderClass