Using functions instead of classes for push sub observers

Author: emawby

example/lib/main.dart

@@ -13,7 +13,6 @@ class MyApp extends StatefulWidget {
 
 class _MyAppState extends State<MyApp>
     with
-        OneSignalPushSubscriptionObserver,
         OneSignalNotificationLifecycleListener,
         OneSignalNotificationClickListener {
   String _debugLabelString = "";
@@ -50,7 +49,12 @@ class _MyAppState extends State<MyApp>
 
     OneSignal.Notifications.clearAll();
 
-    OneSignal.User.pushSubscription.addObserver(this);
+    OneSignal.User.pushSubscription.addObserver((state) {
+      print(OneSignal.User.pushSubscription.optedIn);
+      print(OneSignal.User.pushSubscription.id);
+      print(OneSignal.User.pushSubscription.token);
+      print(state.current.jsonRepresentation());
+    });
 
     OneSignal.Notifications.addPermissionObserver((state) {
       print("Has permission " + state.toString());
@@ -93,13 +97,6 @@ class _MyAppState extends State<MyApp>
     OneSignal.InAppMessages.paused(false);
   }
 
-  void onOSPushSubscriptionChange(OSPushSubscriptionChangedState state) {
-    print(OneSignal.User.pushSubscription.optedIn);
-    print(OneSignal.User.pushSubscription.id);
-    print(OneSignal.User.pushSubscription.token);
-    print(state.current.jsonRepresentation());
-  }
-
   void onClickNotification(OSNotificationClickEvent event) {
     print('NOTIFICATION CLICK LISTENER CALLED WITH EVENT: $event');
     this.setState(() {

lib/src/pushsubscription.dart

@@ -2,15 +2,18 @@ import 'dart:async';
 import 'package:flutter/services.dart';
 import 'package:onesignal_flutter/src/subscription.dart';
 
+typedef void OnPushSubscriptionChangeObserver(
+    OSPushSubscriptionChangedState stateChanges);
+
 class OneSignalPushSubscription {
   MethodChannel _channel = const MethodChannel('OneSignal#pushsubscription');
 
   String? _id;
   String? _token;
   bool? _optedIn;
 
-  List<OneSignalPushSubscriptionObserver> _observers =
-      <OneSignalPushSubscriptionObserver>[];
+  List<OnPushSubscriptionChangeObserver> _observers =
+      <OnPushSubscriptionChangeObserver>[];
   // constructor method
   OneSignalPushSubscription() {
     this._channel.setMethodCallHandler(_handleMethod);
@@ -49,12 +52,12 @@ class OneSignalPushSubscription {
   /// The OSPushSubscriptionObserver.onOSPushSubscriptionChanged method will be fired on the passed-in
   // object when the push subscription changes. This method returns the current OSPushSubscriptionState
   // at the time of adding this observer.
-  void addObserver(OneSignalPushSubscriptionObserver observer) {
+  void addObserver(OnPushSubscriptionChangeObserver observer) {
     _observers.add(observer);
   }
 
   // Remove a push subscription observer that has been previously added.
-  void removeObserver(OneSignalPushSubscriptionObserver observer) {
+  void removeObserver(OnPushSubscriptionChangeObserver observer) {
     _observers.remove(observer);
   }
 
@@ -81,12 +84,7 @@ class OneSignalPushSubscription {
     this._optedIn = stateChanges.current.optedIn;
 
     for (var observer in _observers) {
-      observer.onOSPushSubscriptionChange(stateChanges);
+      observer(stateChanges);
     }
   }
 }
-
-class OneSignalPushSubscriptionObserver {
-  void onOSPushSubscriptionChange(
-      OSPushSubscriptionChangedState stateChanges) {}
-}