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]!
-          .sort(_sortByCreatedAt as int Function(Message, Message)?);
+      newThreads[parentId]!.sort(_sortByCreatedAt);
     } 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) {
-    if (a.createdAt == null) {
-      return 1;
-    }
-
-    if (b.createdAt == null) {
-      return -1;
-    }
-
-    return a.createdAt.compareTo(b.createdAt);
-  }
+  int _sortByCreatedAt(Message a, Message b) =>
+      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
-        .map((it) => it.channel)
-        .where((it) => it != null) as Iterable<ChannelModel>;
+    final channels = cleanedChannelStates.map((it) => it.channel).withNullifyer;
 
-    final reactions =
-        cleanedChannelStates.expand((it) => it.messages).expand((it) => [
+    final reactions = cleanedChannelStates
+        .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
+      ];
+}