feat: remove error generic type

BREAKING CHANGE: user must remove E type from their code

README.md

@@ -7,19 +7,19 @@ background. Inspired by [Revolut's RxData library](https://github.com/revolut-mo
 
 ```shell
 flutter pub add rxdata
-flutter pub add flutter_bloc
 ```
 
 ## Usage
 
-First, define `DataDelagete` object and specify `Data` type and `Exception` type.
+First, define `DataDelagete` object and specify `Data` type.
 
 ```dart
 
 final dataDelegate = DataDelegate<ApiResponse, Exception>(
   fromNetwork: () async* {
+    // [fromNetwork] can yield multiple values before closing. You can sequentially fetch data and 
+    // and yield them step by step.
     final response = await getRequest();
-
     yield response;
   },
   fromStorage: () async {
@@ -38,19 +38,21 @@ You can also use `DataListener` and `DataConsumer`.
 class ExampleWidget extends StatelessWidget {
   const ExampleWidget({Key? key, required this.dataDelegate}) : super(key: key);
 
-  final DataDelegate<ApiResponse, Exception> dataDelegate;
+  final DataDelegate<ApiResponse> dataDelegate;
 
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-      body: DataBuilder<ApiResponse, Exception>(
+      body: DataBuilder<ApiResponse>(
         bloc: dataDelegate,
         builder: (context, state) {
-          if (state.hasValue) {
-            return Text(state.value!.toString());
-          } else {
-            return Text('No data');
-          }
+          return Column(
+            children: [
+              if (state.isLoading) const CircularProgressIndicator(),
+              if (state.hasError) Text(state.error!.toString()),
+              if (state.hasValue) Text(state.value!.toString()),
+            ],
+          );
         },
       ),
     );
@@ -68,4 +70,5 @@ class ExampleWidget extends StatelessWidget {
 You can then call `dataDelegate.reload()` to fetch data again. Delegate will handle caching by
 itself, provided that you specified your callbacks.
 
-See `example` project for full usage.
+See [example project](https://github.com/vaetas/rxdata/blob/main/example/lib/main.dart) for full
+usage.

example/lib/main.dart

@@ -36,7 +36,7 @@ class HomeScreen extends StatefulWidget {
 }
 
 class _HomeScreenState extends State<HomeScreen> {
-  late final DataDelegate<ApiResponse, Object> dataDelegate;
+  late final DataDelegate<ApiResponse> dataDelegate;
 
   bool wasErrorThrown = false;
 
@@ -79,6 +79,9 @@ class _HomeScreenState extends State<HomeScreen> {
         );
       },
       fromStorage: () async {
+        // Uncomment line below to simulate storage IO failure.
+        // throw Exception('Failed to load from storage');
+
         print('[_HomeScreenState.initState] fromStorage');
         final box = await Hive.openBox<String>('storage');
         final data = box.get('data');
@@ -103,7 +106,7 @@ class _HomeScreenState extends State<HomeScreen> {
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-      body: DataBuilder<ApiResponse, Object>(
+      body: DataBuilder<ApiResponse>(
         bloc: dataDelegate,
         builder: (context, state) {
           return CustomScrollView(

example/pubspec.lock

@@ -241,7 +241,7 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "0.2.2"
+    version: "0.2.1"
   sky_engine:
     dependency: transitive
     description: flutter

lib/src/builder.dart

@@ -3,22 +3,22 @@ import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:rxdata/rxdata.dart';
 
 /// Wrapper around [BlocBuilder] for shorter generics definition.
-class DataBuilder<V, E> extends BlocBuilder<DataDelegate<V, E>, Data<V, E>> {
+class DataBuilder<V> extends BlocBuilder<DataDelegate<V>, Data<V>> {
   const DataBuilder({
     Key? key,
-    required BlocWidgetBuilder<Data<V, E>> builder,
-    DataDelegate<V, E>? bloc,
-    BlocBuilderCondition<Data<V, E>>? buildWhen,
+    required BlocWidgetBuilder<Data<V>> builder,
+    DataDelegate<V>? bloc,
+    BlocBuilderCondition<Data<V>>? buildWhen,
   }) : super(key: key, bloc: bloc, buildWhen: buildWhen, builder: builder);
 }
 
 /// Wrapper around [BlocListener] for shorter generics definition.
-class DataListener<V, E> extends BlocListener<DataDelegate<V, E>, Data<V, E>> {
+class DataListener<V> extends BlocListener<DataDelegate<V>, Data<V>> {
   const DataListener({
     Key? key,
-    required BlocWidgetListener<Data<V, E>> listener,
-    DataDelegate<V, E>? bloc,
-    BlocListenerCondition<Data<V, E>>? listenWhen,
+    required BlocWidgetListener<Data<V>> listener,
+    DataDelegate<V>? bloc,
+    BlocListenerCondition<Data<V>>? listenWhen,
     Widget? child,
   }) : super(
           key: key,
@@ -30,14 +30,14 @@ class DataListener<V, E> extends BlocListener<DataDelegate<V, E>, Data<V, E>> {
 }
 
 /// Wrapper around [BlocConsumer] for shorter generics definition.
-class DataConsumer<V, E> extends BlocConsumer<DataDelegate<V, E>, Data<V, E>> {
+class DataConsumer<V> extends BlocConsumer<DataDelegate<V>, Data<V>> {
   const DataConsumer({
     Key? key,
-    required BlocWidgetListener<Data<V, E>> listener,
-    required BlocWidgetBuilder<Data<V, E>> builder,
-    DataDelegate<V, E>? bloc,
-    BlocListenerCondition<Data<V, E>>? listenWhen,
-    BlocBuilderCondition<Data<V, E>>? buildWhen,
+    required BlocWidgetListener<Data<V>> listener,
+    required BlocWidgetBuilder<Data<V>> builder,
+    DataDelegate<V>? bloc,
+    BlocListenerCondition<Data<V>>? listenWhen,
+    BlocBuilderCondition<Data<V>>? buildWhen,
   }) : super(
           key: key,
           listener: listener,

lib/src/data.dart

@@ -1,8 +1,5 @@
 /// Wrapper around your data of type [V].
-///
-/// [E] is a type for a possible exceptions. You can either provide your own
-/// exception class/enum or use [Object].
-class Data<V, E> {
+class Data<V> {
   const Data({
     this.value,
     this.error,
@@ -13,7 +10,7 @@ class Data<V, E> {
   final V? value;
 
   /// Current error
-  final E? error;
+  final Object? error;
 
   /// Whether you can except the data to refresh soon. Remember that you can
   /// have [isLoading] set to true and still have some value and/or error at the
@@ -27,9 +24,9 @@ class Data<V, E> {
   bool get hasError => error != null;
 
   /// Create copy of this [Data] object with new params.
-  Data<V, E> copyWith({
+  Data<V> copyWith({
     V? value,
-    E? error,
+    Object? error,
     bool? isLoading,
   }) {
     return Data(

lib/src/delegate.dart

@@ -2,15 +2,15 @@ import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:rxdata/src/data.dart';
 
 /// Delegates fetching and caching behavior of specified [Data] object.
-class DataDelegate<V, E> extends Cubit<Data<V, E>> {
+class DataDelegate<V> extends Cubit<Data<V>> {
   DataDelegate({
     required this.fromNetwork,
     this.fromMemory,
     this.toMemory,
     this.fromStorage,
     this.toStorage,
     this.onClearCache,
-  }) : super(Data<V, E>(isLoading: true)) {
+  }) : super(Data<V>(isLoading: true)) {
     _init();
   }
 
@@ -37,22 +37,29 @@ class DataDelegate<V, E> extends Cubit<Data<V, E>> {
   bool _locked = false;
 
   Future<void> _init() async {
-    final memoryValue = fromMemory?.call();
-    if (memoryValue != null) {
-      emit(Data(value: memoryValue));
-    } else {
-      await _loadFromStorage();
+    try {
+      final memoryValue = fromMemory?.call();
+      if (memoryValue != null) {
+        emit(Data(value: memoryValue));
+      } else {
+        await _loadFromStorage();
+      }
+    } catch (e, s) {
+      onError(e, s);
     }
 
     await _fetch();
   }
 
   Future<void> _loadFromStorage() async {
-    final value = await fromStorage?.call();
-
-    if (value != null) {
-      emit(state.copyWith(value: value));
-      toMemory?.call(value);
+    try {
+      final value = await fromStorage?.call();
+      if (value != null) {
+        emit(state.copyWith(value: value));
+        toMemory?.call(value);
+      }
+    } catch (e, s) {
+      onError(e, s);
     }
   }
 
@@ -74,24 +81,8 @@ class DataDelegate<V, E> extends Cubit<Data<V, E>> {
         toMemory?.call(event);
         await toStorage?.call(event);
       }
-    } catch (e) {
-      if (e is E) {
-        // .copyWith throws a type error once in a time:
-        // type '_Exception' is not a subtype of type 'Null' of 'error'
-
-        // emit(state.copyWith(error: e as E));
-        emit(
-          Data(
-            value: state.value,
-            error: e as E,
-          ),
-        );
-      } else {
-        throw ArgumentError(
-          'Exception ${e.runtimeType} is not subtype of E in Data<V, E>.'
-          'Ensure you only throw exceptions of type E.',
-        );
-      }
+    } catch (e, s) {
+      onError(e, s);
     } finally {
       emit(state.copyWith(isLoading: false));
     }
@@ -121,6 +112,13 @@ class DataDelegate<V, E> extends Cubit<Data<V, E>> {
   Future<void> clearCache() async {
     await onClearCache?.call();
   }
+
+  @override
+  void onError(Object error, StackTrace stackTrace) {
+    print('[DataDelegate.onError] ERROR: $error');
+    emit(state.copyWith(error: error));
+    super.onError(error, stackTrace);
+  }
 }
 
 typedef _FromNetwork<V> = Stream<V> Function();