feat: add support for keepPreviousData & examples regarding this

packages/fl_query/.flutter-plugins-dependencies

@@ -1 +1 @@
-{"info":"This is a generated file; do not edit or check into version control.","plugins":{"ios":[{"name":"connectivity_plus","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus-2.3.5/","native_build":true,"dependencies":[]}],"android":[{"name":"connectivity_plus","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus-2.3.5/","native_build":true,"dependencies":[]}],"macos":[{"name":"connectivity_plus_macos","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus_macos-1.2.4/","native_build":true,"dependencies":[]}],"linux":[{"name":"connectivity_plus_linux","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus_linux-1.3.1/","native_build":false,"dependencies":[]}],"windows":[{"name":"connectivity_plus_windows","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus_windows-1.2.2/","native_build":true,"dependencies":[]}],"web":[{"name":"connectivity_plus_web","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus_web-1.2.2/","dependencies":[]}]},"dependencyGraph":[{"name":"connectivity_plus","dependencies":["connectivity_plus_linux","connectivity_plus_macos","connectivity_plus_web","connectivity_plus_windows"]},{"name":"connectivity_plus_linux","dependencies":[]},{"name":"connectivity_plus_macos","dependencies":[]},{"name":"connectivity_plus_web","dependencies":[]},{"name":"connectivity_plus_windows","dependencies":[]}],"date_created":"2022-08-04 09:09:34.759333","version":"3.0.1"}
+{"info":"This is a generated file; do not edit or check into version control.","plugins":{"ios":[{"name":"connectivity_plus","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus-2.3.5/","native_build":true,"dependencies":[]}],"android":[{"name":"connectivity_plus","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus-2.3.5/","native_build":true,"dependencies":[]}],"macos":[{"name":"connectivity_plus_macos","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus_macos-1.2.4/","native_build":true,"dependencies":[]}],"linux":[{"name":"connectivity_plus_linux","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus_linux-1.3.1/","native_build":false,"dependencies":[]}],"windows":[{"name":"connectivity_plus_windows","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus_windows-1.2.2/","native_build":true,"dependencies":[]}],"web":[{"name":"connectivity_plus_web","path":"/home/krtirtho/.pub-cache/hosted/pub.dartlang.org/connectivity_plus_web-1.2.2/","dependencies":[]}]},"dependencyGraph":[{"name":"connectivity_plus","dependencies":["connectivity_plus_linux","connectivity_plus_macos","connectivity_plus_web","connectivity_plus_windows"]},{"name":"connectivity_plus_linux","dependencies":[]},{"name":"connectivity_plus_macos","dependencies":[]},{"name":"connectivity_plus_web","dependencies":[]},{"name":"connectivity_plus_windows","dependencies":[]}],"date_created":"2022-08-07 10:53:50.758755","version":"3.0.1"}

packages/fl_query/example/lib/components/query_previous_data.dart

@@ -0,0 +1,70 @@
+import 'dart:convert';
+
+import 'package:fl_query/fl_query.dart';
+import 'package:flutter/material.dart';
+import 'package:http/http.dart' as http;
+
+final todoJob = QueryJob.withVariableKey<Map, void>(
+  preQueryKey: "todo",
+  task: (queryKey, _) async {
+    final res = await http.get(
+      Uri.parse(
+          "https://jsonplaceholder.typicode.com/todos/${getVariable(queryKey)}"),
+    );
+    return jsonDecode(res.body);
+  },
+  keepPreviousData: true,
+);
+
+class QueryPreviousDataExample extends StatefulWidget {
+  const QueryPreviousDataExample({Key? key}) : super(key: key);
+
+  @override
+  State<QueryPreviousDataExample> createState() =>
+      _QueryPreviousDataExampleState();
+}
+
+class _QueryPreviousDataExampleState extends State<QueryPreviousDataExample> {
+  int id = 1;
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Text(
+          "# Query Variable Key with keepPreviousData",
+          style: Theme.of(context).textTheme.headline5,
+        ),
+        QueryBuilder(
+            job: todoJob(id.toString()),
+            externalData: null,
+            builder: (context, query) {
+              if (query.hasError) return Text(query.error.toString());
+              if (!query.hasData) return const CircularProgressIndicator();
+              return Text(jsonEncode(query.data ?? {}));
+            }),
+        Row(
+          children: [
+            IconButton(
+              icon: const Icon(Icons.remove),
+              onPressed: () {
+                setState(() {
+                  id -= 1;
+                });
+              },
+            ),
+            IconButton(
+              icon: const Icon(Icons.add),
+              onPressed: () {
+                setState(() {
+                  id += 1;
+                });
+              },
+            ),
+          ],
+        )
+      ],
+    );
+  }
+}

packages/fl_query/example/lib/main.dart

@@ -3,6 +3,7 @@ import 'package:fl_query_example/components/basic_query.dart';
 import 'package:fl_query_example/components/lazy_query.dart';
 import 'package:fl_query_example/components/mutation_variable_key.dart';
 import 'package:fl_query_example/components/query_external_data.dart';
+import 'package:fl_query_example/components/query_previous_data.dart';
 import 'package:fl_query_example/components/query_variable_key.dart';
 import 'package:fl_query/fl_query.dart';
 import 'package:flutter/material.dart';
@@ -53,6 +54,7 @@ class _MyHomePageState extends State<MyHomePage> with WidgetsBindingObserver {
             QueryExternalDataExample(),
             LazyQueryExample(),
             QueryVariableKeyExample(),
+            QueryPreviousDataExample(),
             Divider(),
             BasicMutationExample(),
             MutationVariableKeyExample(),

packages/fl_query/lib/fl_query.dart

@@ -7,4 +7,4 @@ export 'src/mutation.dart';
 export 'src/mutation_builder.dart';
 export 'src/models/query_job.dart';
 export 'src/models/mutation_job.dart';
-export 'src/utils.dart' show isShallowEqual;
+export 'src/utils.dart' show isShallowEqual, getVariable;

packages/fl_query/lib/src/models/query_job.dart

@@ -1,5 +1,6 @@
 import 'package:connectivity_plus/connectivity_plus.dart';
 import 'package:fl_query/src/query.dart';
+import 'package:flutter/widgets.dart';
 
 class QueryJob<T extends Object, Outside> {
   // all params
@@ -7,21 +8,25 @@ class QueryJob<T extends Object, Outside> {
   QueryTaskFunction<T, Outside> task;
   final int? retries;
   final Duration? retryDelay;
-  final T? initialData;
+  T? initialData;
 
   /// If set to false then the initial fetch will not be called & to
   /// start the process the user has to call the refetch first
   final bool? enabled;
 
   // got from global options
-  bool? refetchOnMount;
+  final bool? refetchOnMount;
-  bool? refetchOnReconnect;
+  final bool? refetchOnReconnect;
-  bool? refetchOnExternalDataChange;
+  final bool? refetchOnExternalDataChange;
-  Duration? staleTime;
+  final bool? keepPreviousData;
-  Duration? cacheTime;
+  final Duration? staleTime;
+  final Duration? cacheTime;
 
-  Duration? refetchInterval;
+  final Duration? refetchInterval;
-  Connectivity? connectivity;
+  final Connectivity? connectivity;
+
+  @protected
+  bool isDynamic = false;
 
   QueryJob({
     required String queryKey,
@@ -37,6 +42,7 @@ class QueryJob<T extends Object, Outside> {
     this.refetchOnReconnect,
     this.refetchOnExternalDataChange,
     this.connectivity,
+    this.keepPreviousData,
   }) : _queryKey = queryKey;
 
   String get queryKey => _queryKey;
@@ -60,10 +66,11 @@ class QueryJob<T extends Object, Outside> {
     bool? refetchOnReconnect,
     bool? refetchOnExternalDataChange,
     Connectivity? connectivity,
+    bool? keepPreviousData,
   }) {
     return (String queryKey) {
       if (preQueryKey != null) queryKey = "$preQueryKey#$queryKey";
-      return QueryJob<T, Outside>(
+      final query = QueryJob<T, Outside>(
         queryKey: queryKey,
         task: task,
         retries: retries,
@@ -77,7 +84,10 @@ class QueryJob<T extends Object, Outside> {
         refetchOnReconnect: refetchOnReconnect,
         refetchOnExternalDataChange: refetchOnExternalDataChange,
         connectivity: connectivity,
+        keepPreviousData: keepPreviousData,
       );
+      query.isDynamic = true;
+      return query;
     };
   }
 }

packages/fl_query/lib/src/query.dart

@@ -72,6 +72,8 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
 
   Connectivity _connectivity;
 
+  T? _previousData;
+
   Query({
     required this.queryKey,
     required this.task,
@@ -85,6 +87,7 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
     this.refetchOnReconnect,
     this.refetchInterval,
     this.enabled = true,
+    T? previousData,
     Connectivity? connectivity,
     T? initialData,
     QueryListener<T>? onData,
@@ -92,9 +95,10 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
   })  : _staleTime = staleTime,
         _initialData = initialData,
         _externalData = externalData,
-        status = QueryStatus.idle,
+        status = previousData == null ? QueryStatus.idle : QueryStatus.success,
         _connectivity = connectivity ?? Connectivity(),
-        super(data: initialData) {
+        _previousData = previousData,
+        super(data: previousData ?? initialData) {
     if (onData != null) _onDataListeners.add(onData);
     if (onError != null) _onErrorListeners.add(onError);
 
@@ -107,6 +111,7 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
     QueryJob<T, Outside> options, {
     required super.queryBowl,
     required Outside externalData,
+    T? previousData,
     QueryListener<T>? onData,
     QueryListener<dynamic>? onError,
   })  : queryKey = options.queryKey,
@@ -118,13 +123,14 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
         refetchInterval = options.refetchInterval,
         refetchOnMount = options.refetchOnMount,
         refetchOnReconnect = options.refetchOnReconnect,
-        status = QueryStatus.idle,
+        status = previousData == null ? QueryStatus.idle : QueryStatus.success,
         _connectivity = options.connectivity ?? Connectivity(),
+        _previousData = previousData,
         super(
           cacheTime: options.cacheTime ?? const Duration(minutes: 5),
           retries: options.retries ?? 3,
           retryDelay: options.retryDelay ?? const Duration(milliseconds: 200),
-          data: options.initialData,
+          data: previousData ?? options.initialData,
         ) {
     if (onData != null) _onDataListeners.add(onData);
     if (onError != null) _onErrorListeners.add(onError);
@@ -222,12 +228,20 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
     _onErrorListeners.remove(listener);
   }
 
+  /// fetches data or runs the provided task initially
+  ///
+  /// Once [data] is available it won't run the [task] ever again
+  /// and will only return the available data
+  ///
+  /// If a [fetch] is already running in the background it'll just return
+  /// the current available [data] (which can be nul if no [initialData]
+  /// was provided) instead of running the task to prevent race conditions
   Future<T?> fetch() async {
     if (!enabled) return null;
 
     /// if isLoading/isRefetching is true that means its already fetching/
     /// refetching. So [_execute] again can create a race condition
-    if (isLoading || isRefetching || hasData) return data;
+    if (isLoading || isRefetching || (hasData && !isPreviousData)) return data;
     status = QueryStatus.loading;
     notifyListeners();
     return _execute().then((_) {
@@ -236,6 +250,18 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
     });
   }
 
+  /// refetches a valid or invalid [Query]
+  ///
+  /// When called before calling [fetch] in a [Query] it'll
+  /// automatically run [fetch]
+  ///
+  /// But if it's used to fetch the first data of a non-enabled [Query]
+  /// aka `LazyQuery`, it'll execute the task & will set the status
+  /// `enabled=true`
+  ///
+  /// If a [refetch] is already running in the background it'll just return
+  /// the current available [data] instead of running the task to prevent
+  /// race conditions
   Future<T?> refetch() async {
     /// if isLoading/isRefetching is true that means its already fetching/
     /// refetching. So [_execute] again can create a race condition
@@ -266,14 +292,22 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
     notifyListeners();
   }
 
+  /// Sets the [externalData] from outside of the query
+  ///
+  /// Remember, it's for the very instance of [Query]
+  /// So this won't persist through later UI/[Query] updates
   void setExternalData(Outside externalData) {
     _prevUsedExternalData = _externalData;
     _externalData = externalData;
   }
 
+  /// Resets the query
+  ///
+  /// The values of internal state of the query are reset to the
+  /// initial ones
   void reset() {
     refetchCount = 0;
-    data = _initialData;
+    data = _previousData ?? _initialData;
     error = null;
     fetched = false;
     status = QueryStatus.idle;
@@ -283,8 +317,12 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
     mounts.clear();
   }
 
-  /// Update configurations of the query after already creating the Query
+  /// Update configurations of the query
-  /// instance
+  /// after already creating the Query instance
+  ///
+  /// Remember, it's just for the single query instance
+  /// In the next UI update/render the options will get reset
+  /// to the default ones defined in the [QueryJob] or [QueryBowlScope]
   void updateDefaultOptions({
     Duration? refetchInterval,
     Duration? staleTime,
@@ -310,11 +348,20 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
     notifyListeners();
   }
 
+  /// checks if the application is connected to internet in any mean
+  ///
+  /// It's true when any one this is connected -
+  /// - ethernet
+  /// - mobile
+  /// - wifi
   Future<bool> isInternetConnected() async {
     return isConnectedToInternet(await _connectivity.checkConnectivity());
   }
 
   /// invalidates the query
+  ///
+  /// Forcefully makes the query stale & expired which results in a refetch
+  /// when met conditions
   void invalidate() {
     /// subtracting [staleTime] from [updatedAt] as staleTime=Duration.zero
     /// indicates the query must never become stale but subtracting the
@@ -340,6 +387,9 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
   bool get isLoading => status == QueryStatus.loading;
   bool get isRefetching => status == QueryStatus.refetching;
   bool get isSuccess => status == QueryStatus.success;
+  bool get isPreviousData {
+    return _previousData != null ? _previousData == data : false;
+  }
 
   A? cast<A>() => this is A ? this as A : null;
 
@@ -348,6 +398,10 @@ class Query<T extends Object, Outside> extends BaseOperation<T> {
   @override
   void mount(ValueKey<String> uKey) {
     super.mount(uKey);
+
+    /// refetching on mount if it's set to true
+    /// also checking if the is stale or not
+    /// no need to refetch a valid query for no reason
     if (refetchOnMount == true && isStale) {
       this.isInternetConnected().then((isConnected) async {
         if (isConnected) await refetch();

packages/fl_query/lib/src/query_bowl.dart

@@ -284,11 +284,13 @@ class QueryBowl extends InheritedWidget {
 
   Query<T, Outside> _createQueryWithDefaults<T extends Object, Outside>(
     QueryJob<T, Outside> options,
-    Outside externalData,
+    Outside externalData, [
-  ) {
+    T? previousData,
+  ]) {
     final query = Query<T, Outside>.fromOptions(
       options,
       externalData: externalData,
+      previousData: previousData,
       queryBowl: this,
     );
     query.updateDefaultOptions(
@@ -361,6 +363,7 @@ class QueryBowl extends InheritedWidget {
     required ValueKey<String> key,
     final QueryListener<T>? onData,
     final QueryListener<dynamic>? onError,
+    final T? previousData,
   }) {
     final prevQuery =
         _queries.firstWhereOrNull((q) => q.queryKey == queryJob.queryKey);
@@ -381,7 +384,11 @@ class QueryBowl extends InheritedWidget {
       // mounting the widget that is using the query in the prevQuery
       return prevQuery;
     }
-    final query = _createQueryWithDefaults<T, Outside>(queryJob, externalData);
+    final query = _createQueryWithDefaults<T, Outside>(
+      queryJob,
+      externalData,
+      previousData,
+    );
     if (onData != null) query.addDataListener(onData);
     if (onError != null) query.addErrorListener(onError);
     query.mount(key);

packages/fl_query/lib/src/query_builder.dart

@@ -1,3 +1,5 @@
+// ignore_for_file: invalid_use_of_protected_member
+
 import 'package:fl_query/src/models/query_job.dart';
 import 'package:fl_query/src/query.dart';
 import 'package:fl_query/src/query_bowl.dart';
@@ -43,11 +45,12 @@ class _QueryBuilderState<T extends Object, Outside>
     WidgetsBinding.instance.addPostFrameCallback((_) => init());
   }
 
-  void init([QueryBowl? bowl]) async {
+  void init([T? previousData]) async {
-    bowl ??= QueryBowl.of(context);
+    final bowl = QueryBowl.of(context);
     query = bowl.addQuery<T, Outside>(
       widget.job,
       externalData: widget.externalData,
+      previousData: previousData,
       key: uKey,
       onData: widget.onData,
       onError: widget.onError,
@@ -72,7 +75,17 @@ class _QueryBuilderState<T extends Object, Outside>
     // re-init the query-builder when new queryJob is appended
     if (oldWidget.job.queryKey != widget.job.queryKey) {
       _queryDispose();
-      init();
+
+      /// setting the new query's initial data as prev query's data
+      /// when [job.keepPreviousData] is true and both are dynamic
+      if (oldWidget.job.isDynamic &&
+          widget.job.isDynamic &&
+          oldWidget.job.keepPreviousData == true &&
+          widget.job.keepPreviousData == true) {
+        init(query?.data);
+      } else {
+        init();
+      }
     } else if (oldWidget.externalData != null &&
         widget.externalData != null &&
         !isShallowEqual(oldWidget.externalData!, widget.externalData!)) {

packages/fl_query/lib/src/utils.dart

@@ -50,3 +50,7 @@ bool isConnectedToInternet(ConnectivityResult result) {
     ConnectivityResult.wifi,
   ].contains(result);
 }
+
+String getVariable(String queryKey) {
+  return queryKey.split("#").last;
+}

packages/fl_query/test/query_test.mocks.dart

@@ -4,13 +4,14 @@
 
 import 'dart:async' as _i7;
 
-import 'package:connectivity_plus/connectivity_plus.dart' as _i10;
+import 'package:connectivity_plus/connectivity_plus.dart' as _i11;
 import 'package:fl_query/src/models/mutation_job.dart' as _i9;
 import 'package:fl_query/src/models/query_job.dart' as _i8;
 import 'package:fl_query/src/mutation.dart' as _i4;
 import 'package:fl_query/src/query.dart' as _i3;
 import 'package:fl_query/src/query_bowl.dart' as _i6;
 import 'package:flutter/foundation.dart' as _i5;
+import 'package:flutter/rendering.dart' as _i10;
 import 'package:flutter/widgets.dart' as _i2;
 import 'package:mockito/mockito.dart' as _i1;
 
@@ -100,6 +101,14 @@ class MockQueryBowl extends _i1.Mock implements _i6.QueryBowl {
   _i2.Widget get child => (super.noSuchMethod(Invocation.getter(#child),
       returnValue: _FakeWidget_1()) as _i2.Widget);
   @override
+  _i7.Future<T?> prefetchQuery<T extends Object, Outside>(
+          _i8.QueryJob<T, Outside>? options,
+          {Outside? externalData}) =>
+      (super.noSuchMethod(
+          Invocation.method(
+              #prefetchQuery, [options], {#externalData: externalData}),
+          returnValue: Future<T?>.value()) as _i7.Future<T?>);
+  @override
   _i7.Future<T?> fetchQuery<T extends Object, Outside>(
           _i8.QueryJob<T, Outside>? options,
           {Outside? externalData,
@@ -122,7 +131,8 @@ class MockQueryBowl extends _i1.Mock implements _i6.QueryBowl {
           {Outside? externalData,
           _i2.ValueKey<String>? key,
           _i3.QueryListener<T>? onData,
-          _i3.QueryListener<dynamic>? onError}) =>
+          _i3.QueryListener<dynamic>? onError,
+          T? previousData}) =>
       (super.noSuchMethod(
           Invocation.method(#addQuery, [
             queryJob
@@ -130,7 +140,8 @@ class MockQueryBowl extends _i1.Mock implements _i6.QueryBowl {
             #externalData: externalData,
             #key: key,
             #onData: onData,
-            #onError: onError
+            #onError: onError,
+            #previousData: previousData
           }),
           returnValue: _FakeQuery_2<T, Outside>()) as _i3.Query<T, Outside>);
   @override
@@ -190,7 +201,7 @@ class MockQueryBowl extends _i1.Mock implements _i6.QueryBowl {
           .noSuchMethod(Invocation.method(#toStringShort, []), returnValue: '')
       as String);
   @override
-  void debugFillProperties(_i5.DiagnosticPropertiesBuilder? properties) =>
+  void debugFillProperties(_i10.DiagnosticPropertiesBuilder? properties) =>
       super.noSuchMethod(Invocation.method(#debugFillProperties, [properties]),
           returnValueForMissingStub: null);
   @override
@@ -232,22 +243,22 @@ class MockQueryBowl extends _i1.Mock implements _i6.QueryBowl {
 /// A class which mocks [Connectivity].
 ///
 /// See the documentation for Mockito's code generation for more information.
-class MockConnectivity extends _i1.Mock implements _i10.Connectivity {
+class MockConnectivity extends _i1.Mock implements _i11.Connectivity {
   MockConnectivity() {
     _i1.throwOnMissingStub(this);
   }
 
   @override
-  _i7.Stream<_i10.ConnectivityResult> get onConnectivityChanged =>
+  _i7.Stream<_i11.ConnectivityResult> get onConnectivityChanged =>
       (super.noSuchMethod(Invocation.getter(#onConnectivityChanged),
-              returnValue: Stream<_i10.ConnectivityResult>.empty())
+              returnValue: Stream<_i11.ConnectivityResult>.empty())
-          as _i7.Stream<_i10.ConnectivityResult>);
+          as _i7.Stream<_i11.ConnectivityResult>);
   @override
-  _i7.Future<_i10.ConnectivityResult> checkConnectivity() =>
+  _i7.Future<_i11.ConnectivityResult> checkConnectivity() =>
       (super.noSuchMethod(Invocation.method(#checkConnectivity, []),
-              returnValue: Future<_i10.ConnectivityResult>.value(
+              returnValue: Future<_i11.ConnectivityResult>.value(
-                  _i10.ConnectivityResult.bluetooth))
+                  _i11.ConnectivityResult.bluetooth))
-          as _i7.Future<_i10.ConnectivityResult>);
+          as _i7.Future<_i11.ConnectivityResult>);
 }
 
 /// A class which mocks [QueryJob].
@@ -266,34 +277,16 @@ class MockQueryJobVoidObject extends _i1.Mock
       super.noSuchMethod(Invocation.setter(#task, _task),
           returnValueForMissingStub: null);
   @override
-  set refetchOnMount(bool? _refetchOnMount) =>
+  set initialData(Object? _initialData) =>
-      super.noSuchMethod(Invocation.setter(#refetchOnMount, _refetchOnMount),
+      super.noSuchMethod(Invocation.setter(#initialData, _initialData),
           returnValueForMissingStub: null);
   @override
-  set refetchOnReconnect(bool? _refetchOnReconnect) => super.noSuchMethod(
+  bool get isDynamic =>
-      Invocation.setter(#refetchOnReconnect, _refetchOnReconnect),
+      (super.noSuchMethod(Invocation.getter(#isDynamic), returnValue: false)
-      returnValueForMissingStub: null);
+          as bool);
   @override
-  set refetchOnExternalDataChange(bool? _refetchOnExternalDataChange) =>
+  set isDynamic(bool? _isDynamic) =>
-      super.noSuchMethod(
+      super.noSuchMethod(Invocation.setter(#isDynamic, _isDynamic),
-          Invocation.setter(
-              #refetchOnExternalDataChange, _refetchOnExternalDataChange),
-          returnValueForMissingStub: null);
-  @override
-  set staleTime(Duration? _staleTime) =>
-      super.noSuchMethod(Invocation.setter(#staleTime, _staleTime),
-          returnValueForMissingStub: null);
-  @override
-  set cacheTime(Duration? _cacheTime) =>
-      super.noSuchMethod(Invocation.setter(#cacheTime, _cacheTime),
-          returnValueForMissingStub: null);
-  @override
-  set refetchInterval(Duration? _refetchInterval) =>
-      super.noSuchMethod(Invocation.setter(#refetchInterval, _refetchInterval),
-          returnValueForMissingStub: null);
-  @override
-  set connectivity(_i10.Connectivity? _connectivity) =>
-      super.noSuchMethod(Invocation.setter(#connectivity, _connectivity),
           returnValueForMissingStub: null);
   @override
   String get queryKey =>

packages/fl_query_hooks/example/lib/components/query_hook_previous_data.dart

@@ -0,0 +1,62 @@
+import 'dart:convert';
+
+import 'package:fl_query/fl_query.dart';
+import 'package:fl_query_hooks/fl_query_hooks.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_hooks/flutter_hooks.dart';
+import 'package:http/http.dart' as http;
+
+final todoJob = QueryJob.withVariableKey<Map, void>(
+  preQueryKey: "todo",
+  task: (queryKey, _) async {
+    final res = await http.get(
+      Uri.parse(
+          "https://jsonplaceholder.typicode.com/todos/${getVariable(queryKey)}"),
+    );
+    return jsonDecode(res.body);
+  },
+  keepPreviousData: true,
+);
+
+class QueryHookPreviousDataExample extends HookWidget {
+  const QueryHookPreviousDataExample({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    final id = useState(1);
+    final query =
+        useQuery(job: todoJob(id.value.toString()), externalData: null);
+
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Text(
+          "# Query Variable Key with keepPreviousData",
+          style: Theme.of(context).textTheme.headline5,
+        ),
+        if (query.hasError)
+          Text(query.error.toString())
+        else if (!query.hasData)
+          const CircularProgressIndicator()
+        else
+          Text(jsonEncode(query.data ?? {})),
+        Row(
+          children: [
+            IconButton(
+              icon: const Icon(Icons.remove),
+              onPressed: () {
+                id.value -= 1;
+              },
+            ),
+            IconButton(
+              icon: const Icon(Icons.add),
+              onPressed: () {
+                id.value += 1;
+              },
+            ),
+          ],
+        )
+      ],
+    );
+  }
+}

packages/fl_query_hooks/example/lib/main.dart

@@ -3,6 +3,7 @@ import 'package:fl_query_hooks_example/components/basic_hook_query.dart';
 import 'package:fl_query_hooks_example/components/lazy_hook_query.dart';
 import 'package:fl_query_hooks_example/components/mutation_hook_variable_key.dart';
 import 'package:fl_query_hooks_example/components/query_hook_external_data.dart';
+import 'package:fl_query_hooks_example/components/query_hook_previous_data.dart';
 import 'package:fl_query_hooks_example/components/query_hook_variable_key.dart';
 import 'package:fl_query/fl_query.dart';
 import 'package:flutter/material.dart';
@@ -53,6 +54,7 @@ class _MyHomePageState extends State<MyHomePage> with WidgetsBindingObserver {
             QueryHookExternalDataExample(),
             LazyHookQueryExample(),
             QueryHookVariableKeyExample(),
+            QueryHookPreviousDataExample(),
             Divider(),
             BasicHookMutationExample(),
             MutationHookVariableKeyExample(),

packages/fl_query_hooks/lib/src/use_query.dart

@@ -1,3 +1,5 @@
+// ignore_for_file: invalid_use_of_protected_member
+
 import 'package:fl_query/fl_query.dart';
 import 'package:fl_query_hooks/src/utils.dart';
 import 'package:flutter/widgets.dart';
@@ -31,10 +33,11 @@ Query<T, Outside> useQuery<T extends Object, Outside>({
   final oldOnData = usePrevious(onData);
   final oldOnError = usePrevious(onError);
 
-  final init = useCallback(() {
+  final init = useCallback(([T? previousData]) {
     query.value = queryBowl.addQuery<T, Outside>(
       job,
       externalData: externalData,
+      previousData: previousData,
       key: uKey,
       onData: onData,
       onError: onError,
@@ -66,7 +69,17 @@ Query<T, Outside> useQuery<T extends Object, Outside>({
     final hasOnDataChanged = oldOnData != onData && oldOnData != null;
     if (oldJob != null && oldJob.queryKey != job.queryKey) {
       disposeQuery();
-      init();
+
+      /// setting the new query's initial data as prev query's data
+      /// when [job.keepPreviousData] is true and both are dynamic
+      if (oldJob.isDynamic &&
+          job.isDynamic &&
+          oldJob.keepPreviousData == true &&
+          job.keepPreviousData == true) {
+        init(query.value.data);
+      } else {
+        init();
+      }
     } else if (oldExternalData != null &&
         externalData != null &&
         !isShallowEqual(oldExternalData, externalData)) {