Refactor Bloc to extend Stream<State> (#572)

felangel · Oct 14, 2019 · c9b6674 · c9b6674
1 parent aabcd04
commit c9b6674
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Showing 8 changed files with 115 additions and 63 deletions.
diff --git a/packages/bloc/example/main.dart b/packages/bloc/example/main.dart
@@ -14,12 +14,12 @@ class CounterBloc extends Bloc<CounterEvent, int> {
       case CounterEvent.decrement:
         // Simulating Network Latency
         await Future<void>.delayed(Duration(seconds: 1));
-        yield currentState - 1;
+        yield state - 1;
         break;
       case CounterEvent.increment:
         // Simulating Network Latency
         await Future<void>.delayed(Duration(milliseconds: 500));
-        yield currentState + 1;
+        yield state + 1;
         break;
       default:
         throw Exception('unhandled event: $event');

diff --git a/packages/bloc/lib/src/bloc.dart b/packages/bloc/lib/src/bloc.dart
@@ -6,26 +6,42 @@ import 'package:rxdart/rxdart.dart';
 
 /// Takes a [Stream] of [Event]s as input
 /// and transforms them into a [Stream] of [State]s as output.
-abstract class Bloc<Event, State> {
+abstract class Bloc<Event, State> extends Stream<State> {
   final PublishSubject<Event> _eventSubject = PublishSubject<Event>();
 
   BehaviorSubject<State> _stateSubject;
 
-  /// Returns [Stream] of [State]s.
-  /// Usually consumed by the presentation layer.
-  Stream<State> get state => _stateSubject.stream;
+  /// Returns the current [State] of the [Bloc].
+  State get state => _stateSubject.value;
 
   /// Returns the [State] before any [Event]s have been `dispatched`.
   State get initialState;
 
-  /// Returns the current [State] of the [Bloc].
-  State get currentState => _stateSubject.value;
+  /// Returns whether the `Stream<State>` is a broadcast stream.
+  bool get isBroadcast => _stateSubject.isBroadcast;
 
   Bloc() {
     _stateSubject = BehaviorSubject<State>.seeded(initialState);
     _bindStateSubject();
   }
 
+  /// Adds a subscription to the `Stream<State>`.
+  /// Returns a [StreamSubscription] which handles events from the `Stream<State>`
+  /// using the provided [onData], [onError] and [onDone] handlers.
+  StreamSubscription<State> listen(
+    void onData(State value), {
+    Function onError,
+    void onDone(),
+    bool cancelOnError,
+  }) {
+    return _stateSubject.listen(
+      onData,
+      onError: onError,
+      onDone: onDone,
+      cancelOnError: cancelOnError,
+    );
+  }
+
   /// Called whenever an [Event] is dispatched to the [Bloc].
   /// A great spot to add logging/analytics at the individual [Bloc] level.
   void onEvent(Event event) => null;
@@ -136,9 +152,9 @@ abstract class Bloc<Event, State> {
       return mapEventToState(currentEvent).handleError(_handleError);
     })).forEach(
       (State nextState) {
-        if (currentState == nextState || _stateSubject.isClosed) return;
+        if (state == nextState || _stateSubject.isClosed) return;
         final transition = Transition(
-          currentState: currentState,
+          currentState: state,
           event: currentEvent,
           nextState: nextState,
         );

diff --git a/packages/bloc/test/bloc_delegate_test.dart b/packages/bloc/test/bloc_delegate_test.dart
@@ -23,7 +23,7 @@ void main() {
       when(delegate.onEvent(any, any)).thenReturn(null);
 
       expectLater(
-        complexBloc.state,
+        complexBloc,
         emitsInOrder(expectedStateAfterEventB),
       ).then((dynamic _) {
         verify(
@@ -53,7 +53,7 @@ void main() {
       when(delegate.onEvent(any, any)).thenReturn(null);
 
       expectLater(
-        complexBlocA.state,
+        complexBlocA,
         emitsInOrder(expectedStateAfterEventB),
       ).then((dynamic _) {
         verify(
@@ -65,7 +65,7 @@ void main() {
       });
 
       expectLater(
-        complexBlocB.state,
+        complexBlocB,
         emitsInOrder(expectedStateAfterEventC),
       ).then((dynamic _) {
         verify(
@@ -91,7 +91,7 @@ void main() {
       when(delegate.onEvent(any, any)).thenReturn(null);
 
       expectLater(
-        complexBloc.state,
+        complexBloc,
         emitsInOrder(expectedStateAfterEventB),
       ).then((dynamic _) {
         verifyNever(
@@ -121,7 +121,7 @@ void main() {
       when(delegate.onTransition(any, any)).thenReturn(null);
 
       expectLater(
-        complexBloc.state,
+        complexBloc,
         emitsInOrder(expectedStateAfterEventB),
       ).then((dynamic _) {
         verify(
@@ -155,7 +155,7 @@ void main() {
       when(delegate.onTransition(any, any)).thenReturn(null);
 
       expectLater(
-        complexBlocA.state,
+        complexBlocA,
         emitsInOrder(expectedStateAfterEventB),
       ).then((dynamic _) {
         verify(
@@ -171,7 +171,7 @@ void main() {
       });
 
       expectLater(
-        complexBlocB.state,
+        complexBlocB,
         emitsInOrder(expectedStateAfterEventC),
       ).then((dynamic _) {
         verify(
@@ -201,7 +201,7 @@ void main() {
       when(delegate.onTransition(any, any)).thenReturn(null);
 
       expectLater(
-        complexBloc.state,
+        complexBloc,
         emitsInOrder(expectedStateAfterEventB),
       ).then((dynamic _) {
         verifyNever(
@@ -238,7 +238,10 @@ void main() {
         errorHandled = true;
       });
 
-      expectLater(_bloc.state, emitsInOrder(<int>[0])).then((dynamic _) {
+      expectLater(
+        _bloc,
+        emitsInOrder(<int>[0]),
+      ).then((dynamic _) {
         expect(errorHandled, isTrue);
         expect(blocWithError, _bloc);
       });