fix example

Signed-off-by: Sahil Kumar <[email protected]>

packages/stream_chat/lib/src/api/channel.dart

@@ -1685,8 +1685,7 @@ class ChannelClientState {
         ...messages!,
       ];
 
-      newThreads[parentId]!
+      newThreads[parentId]!.sort(_sortByCreatedAt);
-          .sort(_sortByCreatedAt as int Function(Message, Message)?);
     } else {
       newThreads[parentId] = messages;
     }
@@ -1713,7 +1712,7 @@ class ChannelClientState {
                   .any((newMessage) => newMessage.id == m.id) !=
               true)
           .toList(),
-    ]..sort(_sortByCreatedAt as int Function(Message, Message)?);
+    ]..sort(_sortByCreatedAt);
 
     final newWatchers = <User>[
       ...updatedState.watchers,
@@ -1752,17 +1751,8 @@ class ChannelClientState {
     );
   }
 
-  int? _sortByCreatedAt(a, b) {
+  int _sortByCreatedAt(Message a, Message b) =>
-    if (a.createdAt == null) {
+      a.createdAt.compareTo(b.createdAt);
-      return 1;
-    }
-
-    if (b.createdAt == null) {
-      return -1;
-    }
-
-    return a.createdAt.compareTo(b.createdAt);
-  }
 
   /// The channel state related to this client
   ChannelState get _channelState => _channelStateController.value!;

packages/stream_chat/lib/src/db/chat_persistence_client.dart

@@ -7,6 +7,7 @@ import 'package:stream_chat/src/models/message.dart';
 import 'package:stream_chat/src/models/reaction.dart';
 import 'package:stream_chat/src/models/read.dart';
 import 'package:stream_chat/src/models/user.dart';
+import 'package:stream_chat/src/extensions/iterable_extension.dart';
 
 /// A simple client used for persisting chat data locally.
 abstract class ChatPersistenceClient {
@@ -78,7 +79,7 @@ abstract class ChatPersistenceClient {
     return ChannelState(
       members: data[0] as List<Member>,
       read: data[1] as List<Read>,
-      channel: data[2] as ChannelModel,
+      channel: data[2] as ChannelModel?,
       messages: data[3] as List<Message>,
       pinnedMessages: data[4] as List<Message>,
     );
@@ -192,17 +193,17 @@ abstract class ChatPersistenceClient {
       deleteMembers,
     ]);
 
-    final channels = cleanedChannelStates
+    final channels = cleanedChannelStates.map((it) => it.channel).withNullifyer;
-        .map((it) => it.channel)
-        .where((it) => it != null) as Iterable<ChannelModel>;
 
-    final reactions =
+    final reactions = cleanedChannelStates
-        cleanedChannelStates.expand((it) => it.messages).expand((it) => [
+        .expand((it) => it.messages)
+        .expand((it) => [
               if (it.ownReactions != null)
                 ...it.ownReactions!.where((r) => r.userId != null),
               if (it.latestReactions != null)
                 ...it.latestReactions!.where((r) => r.userId != null),
-            ]);
+            ])
+        .withNullifyer;
 
     final users = cleanedChannelStates
         .map((cs) => [
@@ -220,7 +221,7 @@ abstract class ChatPersistenceClient {
               ...cs.members.map((m) => m.user),
             ])
         .expand((it) => it)
-        .where((it) => it != null) as Iterable<User>;
+        .withNullifyer;
 
     final updateMessagesFuture = cleanedChannelStates.map((it) {
       final cid = it.channel!.cid;

packages/stream_chat/lib/src/extensions/iterable_extension.dart

@@ -0,0 +1,9 @@
+/// Useful extension functions for [Iterable]
+extension IterableX<T> on Iterable<T?> {
+  /// Removes all the null values
+  /// and converts `Iterable<T?>` into `Iterable<T>`
+  Iterable<T> get withNullifyer => [
+        for (final item in this)
+          if (item != null) item
+      ];
+}

packages/stream_chat_persistence/example/lib/main.dart

@@ -50,15 +50,16 @@ Future<void> main() async {
 
 /// Example using Stream's Low Level Dart client.
 class StreamExample extends StatelessWidget {
-  /// To initialize this example, an instance of [client] and [channel] is required.
+  /// To initialize this example, an instance of
+  /// [client] and [channel] is required.
   const StreamExample({
-    Key key,
+    Key? key,
-    @required this.client,
+    required this.client,
-    @required this.channel,
+    required this.channel,
   }) : super(key: key);
 
-  /// Instance of [StreamChatClient] we created earlier. This contains information about
+  /// Instance of [StreamChatClient] we created earlier.
-  /// our application and connection state.
+  /// This contains information about our application and connection state.
   final StreamChatClient client;
 
   /// The channel we'd like to observe and participate.
@@ -77,28 +78,31 @@ class StreamExample extends StatelessWidget {
 /// containing the channel name and a [MessageView] displaying recent messages.
 class HomeScreen extends StatelessWidget {
   /// [HomeScreen] is constructed using the [Channel] we defined earlier.
-  const HomeScreen({Key key, @required this.channel}) : super(key: key);
+  const HomeScreen({
+    Key? key,
+    required this.channel,
+  }) : super(key: key);
 
   /// Channel object containing the [Channel.id] we'd like to observe.
   final Channel channel;
 
   @override
   Widget build(BuildContext context) {
-    final messages = channel.state.channelStateStream;
+    final messages = channel.state!.channelStateStream;
     return Scaffold(
       appBar: AppBar(
         title: Text('Channel: ${channel.id}'),
       ),
       body: SafeArea(
-        child: StreamBuilder<ChannelState>(
+        child: StreamBuilder<ChannelState?>(
           stream: messages,
           builder: (
             BuildContext context,
-            AsyncSnapshot<ChannelState> snapshot,
+            AsyncSnapshot<ChannelState?> snapshot,
           ) {
             if (snapshot.hasData && snapshot.data != null) {
               return MessageView(
-                messages: snapshot.data.messages.reversed.toList(),
+                messages: snapshot.data!.messages.reversed.toList(),
                 channel: channel,
               );
             } else if (snapshot.hasError) {
@@ -110,8 +114,8 @@ class HomeScreen extends StatelessWidget {
             }
             return const Center(
               child: SizedBox(
-                width: 100.0,
+                width: 100,
-                height: 100.0,
+                height: 100,
                 child: CircularProgressIndicator(),
               ),
             );
@@ -127,9 +131,9 @@ class HomeScreen extends StatelessWidget {
 class MessageView extends StatefulWidget {
   /// Message takes the latest list of messages and the current channel.
   const MessageView({
-    Key key,
+    Key? key,
-    @required this.messages,
+    required this.messages,
-    @required this.channel,
+    required this.channel,
   }) : super(key: key);
 
   /// List of messages sent in the given channel.
@@ -143,8 +147,8 @@ class MessageView extends StatefulWidget {
 }
 
 class _MessageViewState extends State<MessageView> {
-  TextEditingController _controller;
+  late final TextEditingController _controller;
-  ScrollController _scrollController;
+  late final ScrollController _scrollController;
 
   List<Message> get _messages => widget.messages;
 
@@ -182,20 +186,20 @@ class _MessageViewState extends State<MessageView> {
             reverse: true,
             itemBuilder: (BuildContext context, int index) {
               final item = _messages[index];
-              if (item.user.id == widget.channel.client.uid) {
+              if (item.user?.id == widget.channel.client.uid) {
                 return Align(
                   alignment: Alignment.centerRight,
                   child: Padding(
-                    padding: const EdgeInsets.all(8.0),
+                    padding: const EdgeInsets.all(8),
-                    child: Text(item.text),
+                    child: Text(item.text ?? ''),
                   ),
                 );
               } else {
                 return Align(
                   alignment: Alignment.centerLeft,
                   child: Padding(
-                    padding: const EdgeInsets.all(8.0),
+                    padding: const EdgeInsets.all(8),
-                    child: Text(item.text),
+                    child: Text(item.text ?? ''),
                   ),
                 );
               }
@@ -203,7 +207,7 @@ class _MessageViewState extends State<MessageView> {
           ),
         ),
         Padding(
-          padding: const EdgeInsets.all(8.0),
+          padding: const EdgeInsets.all(8),
           child: Row(
             children: [
               Expanded(
@@ -251,7 +255,8 @@ class _MessageViewState extends State<MessageView> {
   }
 }
 
-/// Helper extension for quickly retrieving the current user id from a [StreamChatClient].
+/// Helper extension for quickly retrieving
+/// the current user id from a [StreamChatClient].
 extension on StreamChatClient {
-  String get uid => state.user.id;
+  String get uid => state.user!.id;
 }

packages/stream_chat_persistence/example/pubspec.yaml

@@ -5,7 +5,7 @@ publish_to: 'none'
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.7.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   flutter: