iOS: Migrate FlutterEngine to ARC (flutter/engine#55590)

Migrates `FlutterEnging` from manual reference counting to ARC. Migrates properties from `retain` to strong and `assign` to `weak` (where referencing an Obj-C object).

No semantic changes, therefore no changes to tests.

Issue: https://github.com/flutter/flutter/issues/137801

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

engine/src/flutter/shell/platform/darwin/ios/BUILD.gn

@@ -70,7 +70,9 @@ source_set("flutter_framework_source_arc") {
     "framework/Source/FlutterDartVMServicePublisher.mm",
     "framework/Source/FlutterEmbedderKeyResponder.h",
     "framework/Source/FlutterEmbedderKeyResponder.mm",
+    "framework/Source/FlutterEngine.mm",
     "framework/Source/FlutterEngineGroup.mm",
+    "framework/Source/FlutterEngine_Internal.h",
     "framework/Source/FlutterHeadlessDartRunner.mm",
     "framework/Source/FlutterKeyPrimaryResponder.h",
     "framework/Source/FlutterKeySecondaryResponder.h",
@@ -186,8 +188,6 @@ source_set("flutter_framework_source") {
     # iOS embedder is migrating to ARC.
     # New files are highly encouraged to be in ARC.
     # To add new files in ARC, add them to the `flutter_framework_source_arc` target.
-    "framework/Source/FlutterEngine.mm",
-    "framework/Source/FlutterEngine_Internal.h",
     "framework/Source/FlutterViewController.mm",
     "framework/Source/FlutterViewController_Internal.h",
     "platform_view_ios.h",

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm

@@ -42,6 +42,8 @@
 #import "flutter/shell/platform/darwin/ios/rendering_api_selection.h"
 #include "flutter/shell/profiling/sampling_profiler.h"
 
+FLUTTER_ASSERT_ARC
+
 /// Inheriting ThreadConfigurer and use iOS platform thread API to configure the thread priorities
 /// Using iOS platform thread API to configure thread priority
 static void IOSPlatformThreadConfigSetter(const fml::Thread::ThreadConfig& config) {
@@ -88,7 +90,7 @@ NSString* const kFlutterKeyDataChannel = @"flutter/keydata";
 static constexpr int kNumProfilerSamplesPerSec = 5;
 
 @interface FlutterEngineRegistrar : NSObject <FlutterPluginRegistrar>
-@property(nonatomic, assign) FlutterEngine* flutterEngine;
+@property(nonatomic, weak) FlutterEngine* flutterEngine;
 - (instancetype)initWithPlugin:(NSString*)pluginKey flutterEngine:(FlutterEngine*)flutterEngine;
 @end
 
@@ -97,6 +99,14 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
                              FlutterTextInputDelegate,
                              FlutterBinaryMessenger,
                              FlutterTextureRegistry>
+
+#pragma mark - Properties
+
+@property(nonatomic, readonly) FlutterDartProject* dartProject;
+@property(nonatomic, readonly, copy) NSString* labelPrefix;
+@property(nonatomic, readonly, assign) BOOL allowHeadlessExecution;
+@property(nonatomic, readonly, assign) BOOL restorationEnabled;
+
 // Maintains a dictionary of plugin names that have registered with the engine.  Used by
 // FlutterEngineRegistrar to implement a FlutterPluginRegistrar.
 @property(nonatomic, readonly) NSMutableDictionary* pluginPublications;
@@ -104,55 +114,53 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
 
 @property(nonatomic, readwrite, copy) NSString* isolateId;
 @property(nonatomic, copy) NSString* initialRoute;
-@property(nonatomic, retain) id<NSObject> flutterViewControllerWillDeallocObserver;
+@property(nonatomic, strong) id<NSObject> flutterViewControllerWillDeallocObserver;
+@property(nonatomic, strong) FlutterDartVMServicePublisher* publisher;
+@property(nonatomic, assign) int64_t nextTextureId;
+
+#pragma mark - Channel properties
+
+@property(nonatomic, strong) FlutterPlatformPlugin* platformPlugin;
+@property(nonatomic, strong) FlutterTextInputPlugin* textInputPlugin;
+@property(nonatomic, strong) FlutterUndoManagerPlugin* undoManagerPlugin;
+@property(nonatomic, strong) FlutterSpellCheckPlugin* spellCheckPlugin;
+@property(nonatomic, strong) FlutterRestorationPlugin* restorationPlugin;
+@property(nonatomic, strong) FlutterMethodChannel* localizationChannel;
+@property(nonatomic, strong) FlutterMethodChannel* navigationChannel;
+@property(nonatomic, strong) FlutterMethodChannel* restorationChannel;
+@property(nonatomic, strong) FlutterMethodChannel* platformChannel;
+@property(nonatomic, strong) FlutterMethodChannel* platformViewsChannel;
+@property(nonatomic, strong) FlutterMethodChannel* textInputChannel;
+@property(nonatomic, strong) FlutterMethodChannel* undoManagerChannel;
+@property(nonatomic, strong) FlutterMethodChannel* scribbleChannel;
+@property(nonatomic, strong) FlutterMethodChannel* spellCheckChannel;
+@property(nonatomic, strong) FlutterBasicMessageChannel* lifecycleChannel;
+@property(nonatomic, strong) FlutterBasicMessageChannel* systemChannel;
+@property(nonatomic, strong) FlutterBasicMessageChannel* settingsChannel;
+@property(nonatomic, strong) FlutterBasicMessageChannel* keyEventChannel;
+@property(nonatomic, strong) FlutterMethodChannel* screenshotChannel;
 
 #pragma mark - Embedder API properties
 
 @property(nonatomic, assign) BOOL enableEmbedderAPI;
 // Function pointers for interacting with the embedder.h API.
 @property(nonatomic) FlutterEngineProcTable& embedderAPI;
+
 @end
 
 @implementation FlutterEngine {
-  fml::scoped_nsobject<FlutterDartProject> _dartProject;
   std::shared_ptr<flutter::ThreadHost> _threadHost;
   std::unique_ptr<flutter::Shell> _shell;
-  NSString* _labelPrefix;
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory;
 
+  // TODO(cbracken): https://github.com/flutter/flutter/issues/155943
+  // Migrate to @property(nonatomic, weak).
   fml::WeakNSObject<FlutterViewController> _viewController;
-  fml::scoped_nsobject<FlutterDartVMServicePublisher> _publisher;
 
   std::shared_ptr<flutter::PlatformViewsController> _platformViewsController;
   flutter::IOSRenderingAPI _renderingApi;
   std::shared_ptr<flutter::ProfilerMetricsIOS> _profiler_metrics;
   std::shared_ptr<flutter::SamplingProfiler> _profiler;
 
-  // Channels
-  fml::scoped_nsobject<FlutterPlatformPlugin> _platformPlugin;
-  fml::scoped_nsobject<FlutterTextInputPlugin> _textInputPlugin;
-  fml::scoped_nsobject<FlutterUndoManagerPlugin> _undoManagerPlugin;
-  fml::scoped_nsobject<FlutterSpellCheckPlugin> _spellCheckPlugin;
-  fml::scoped_nsobject<FlutterRestorationPlugin> _restorationPlugin;
-  fml::scoped_nsobject<FlutterMethodChannel> _localizationChannel;
-  fml::scoped_nsobject<FlutterMethodChannel> _navigationChannel;
-  fml::scoped_nsobject<FlutterMethodChannel> _restorationChannel;
-  fml::scoped_nsobject<FlutterMethodChannel> _platformChannel;
-  fml::scoped_nsobject<FlutterMethodChannel> _platformViewsChannel;
-  fml::scoped_nsobject<FlutterMethodChannel> _textInputChannel;
-  fml::scoped_nsobject<FlutterMethodChannel> _undoManagerChannel;
-  fml::scoped_nsobject<FlutterMethodChannel> _scribbleChannel;
-  fml::scoped_nsobject<FlutterMethodChannel> _spellCheckChannel;
-  fml::scoped_nsobject<FlutterBasicMessageChannel> _lifecycleChannel;
-  fml::scoped_nsobject<FlutterBasicMessageChannel> _systemChannel;
-  fml::scoped_nsobject<FlutterBasicMessageChannel> _settingsChannel;
-  fml::scoped_nsobject<FlutterBasicMessageChannel> _keyEventChannel;
-  fml::scoped_nsobject<FlutterMethodChannel> _screenshotChannel;
-
-  int64_t _nextTextureId;
-
-  BOOL _allowHeadlessExecution;
-  BOOL _restorationEnabled;
   FlutterBinaryMessengerRelay* _binaryMessenger;
   FlutterTextureRegistryRelay* _textureRegistry;
   std::unique_ptr<flutter::ConnectionCollection> _connections;
@@ -190,29 +198,21 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
   _restorationEnabled = restorationEnabled;
   _allowHeadlessExecution = allowHeadlessExecution;
   _labelPrefix = [labelPrefix copy];
+  _dartProject = project ?: [[FlutterDartProject alloc] init];
 
-  _weakFactory = std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(self);
+  _enableEmbedderAPI = _dartProject.settings.enable_embedder_api;
-
-  if (project == nil) {
-    _dartProject.reset([[FlutterDartProject alloc] init]);
-  } else {
-    _dartProject.reset([project retain]);
-  }
-
-  _enableEmbedderAPI = _dartProject.get().settings.enable_embedder_api;
   if (_enableEmbedderAPI) {
     NSLog(@"============== iOS: enable_embedder_api is on ==============");
     _embedderAPI.struct_size = sizeof(FlutterEngineProcTable);
     FlutterEngineGetProcAddresses(&_embedderAPI);
   }
 
-  if (!EnableTracingIfNecessary([_dartProject.get() settings])) {
+  if (!EnableTracingIfNecessary(_dartProject.settings)) {
     NSLog(
         @"Cannot create a FlutterEngine instance in debug mode without Flutter tooling or "
         @"Xcode.\n\nTo launch in debug mode in iOS 14+, run flutter run from Flutter tools, run "
         @"from an IDE with a Flutter IDE plugin or run the iOS project from Xcode.\nAlternatively "
         @"profile and release mode apps can be launched from the home screen.");
-    [self release];
     return nil;
   }
 
@@ -292,35 +292,22 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
                                                       object:self
                                                     userInfo:nil];
 
-  // It will be destroyed and invalidate its weak pointers
+  // nil out weak references.
-  // before any other members are destroyed.
+  // TODO(cbracken): https://github.com/flutter/flutter/issues/156222
-  _weakFactory.reset();
+  // Ensure that FlutterEngineRegistrar is using weak pointers, then eliminate this code.
-
-  /// nil out weak references.
   [_registrars
       enumerateKeysAndObjectsUsingBlock:^(id key, FlutterEngineRegistrar* registrar, BOOL* stop) {
         registrar.flutterEngine = nil;
       }];
 
-  [_labelPrefix release];
-  [_initialRoute release];
-  [_pluginPublications release];
-  [_registrars release];
   _binaryMessenger.parent = nil;
   _textureRegistry.parent = nil;
-  [_binaryMessenger release];
-  [_textureRegistry release];
-  _textureRegistry = nil;
-  [_isolateId release];
 
   NSNotificationCenter* center = [NSNotificationCenter defaultCenter];
   if (_flutterViewControllerWillDeallocObserver) {
     [center removeObserver:_flutterViewControllerWillDeallocObserver];
-    [_flutterViewControllerWillDeallocObserver release];
   }
   [center removeObserver:self];
-
-  [super dealloc];
 }
 
 - (flutter::Shell&)shell {
@@ -328,10 +315,6 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
   return *_shell;
 }
 
-- (fml::WeakNSObject<FlutterEngine>)getWeakNSObject {
-  return _weakFactory->GetWeakNSObject();
-}
-
 - (void)updateViewportMetrics:(flutter::ViewportMetrics)viewportMetrics {
   if (!self.platformView) {
     return;
@@ -429,16 +412,16 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
   self.iosPlatformView->SetOwnerViewController(_viewController);
   [self maybeSetupPlatformViewChannels];
   [self updateDisplays];
-  _textInputPlugin.get().viewController = viewController;
+  self.textInputPlugin.viewController = viewController;
 
   if (viewController) {
-    __block FlutterEngine* blockSelf = self;
+    __weak __block FlutterEngine* weakSelf = self;
     self.flutterViewControllerWillDeallocObserver =
         [[NSNotificationCenter defaultCenter] addObserverForName:FlutterViewControllerWillDealloc
                                                           object:viewController
                                                            queue:[NSOperationQueue mainQueue]
                                                       usingBlock:^(NSNotification* note) {
-                                                        [blockSelf notifyViewControllerDeallocated];
+                                                        [weakSelf notifyViewControllerDeallocated];
                                                       }];
   } else {
     self.flutterViewControllerWillDeallocObserver = nil;
@@ -455,16 +438,15 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
     if (_flutterViewControllerWillDeallocObserver) {
       [[NSNotificationCenter defaultCenter]
           removeObserver:_flutterViewControllerWillDeallocObserver];
-      [_flutterViewControllerWillDeallocObserver release];
     }
-    _flutterViewControllerWillDeallocObserver = [observer retain];
+    _flutterViewControllerWillDeallocObserver = observer;
   }
 }
 
 - (void)notifyViewControllerDeallocated {
-  [[self lifecycleChannel] sendMessage:@"AppLifecycleState.detached"];
+  [self.lifecycleChannel sendMessage:@"AppLifecycleState.detached"];
-  _textInputPlugin.get().viewController = nil;
+  self.textInputPlugin.viewController = nil;
-  if (!_allowHeadlessExecution) {
+  if (!self.allowHeadlessExecution) {
     [self destroyContext];
   } else if (_shell) {
     flutter::PlatformViewIOS* platform_view = [self iosPlatformView];
@@ -472,7 +454,7 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
       platform_view->SetOwnerViewController({});
     }
   }
-  [_textInputPlugin.get() resetViewResponder];
+  [self.textInputPlugin resetViewResponder];
   _viewController.reset();
 }
 
@@ -492,88 +474,46 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
   return _viewController.get();
 }
 
-- (FlutterPlatformPlugin*)platformPlugin {
-  return _platformPlugin.get();
-}
 - (std::shared_ptr<flutter::PlatformViewsController>&)platformViewsController {
   return _platformViewsController;
 }
-- (FlutterTextInputPlugin*)textInputPlugin {
-  return _textInputPlugin.get();
-}
-- (FlutterUndoManagerPlugin*)undoManagerPlugin {
-  return _undoManagerPlugin.get();
-}
-- (FlutterRestorationPlugin*)restorationPlugin {
-  return _restorationPlugin.get();
-}
-- (FlutterMethodChannel*)localizationChannel {
-  return _localizationChannel.get();
-}
-- (FlutterMethodChannel*)navigationChannel {
-  return _navigationChannel.get();
-}
-- (FlutterMethodChannel*)restorationChannel {
-  return _restorationChannel.get();
-}
-- (FlutterMethodChannel*)platformChannel {
-  return _platformChannel.get();
-}
-- (FlutterMethodChannel*)textInputChannel {
-  return _textInputChannel.get();
-}
-- (FlutterMethodChannel*)undoManagerChannel {
-  return _undoManagerChannel.get();
-}
-- (FlutterMethodChannel*)scribbleChannel {
-  return _scribbleChannel.get();
-}
-- (FlutterMethodChannel*)spellCheckChannel {
-  return _spellCheckChannel.get();
-}
-- (FlutterBasicMessageChannel*)lifecycleChannel {
-  return _lifecycleChannel.get();
-}
-- (FlutterBasicMessageChannel*)systemChannel {
-  return _systemChannel.get();
-}
-- (FlutterBasicMessageChannel*)settingsChannel {
-  return _settingsChannel.get();
-}
-- (FlutterBasicMessageChannel*)keyEventChannel {
-  return _keyEventChannel.get();
-}
 
 - (NSURL*)observatoryUrl {
-  return [_publisher.get() url];
+  return self.publisher.url;
 }
 
 - (NSURL*)vmServiceUrl {
-  return [_publisher.get() url];
+  return self.publisher.url;
 }
 
 - (void)resetChannels {
-  _localizationChannel.reset();
+  self.localizationChannel = nil;
-  _navigationChannel.reset();
+  self.navigationChannel = nil;
-  _restorationChannel.reset();
+  self.restorationChannel = nil;
-  _platformChannel.reset();
+  self.platformChannel = nil;
-  _platformViewsChannel.reset();
+  self.platformViewsChannel = nil;
-  _textInputChannel.reset();
+  self.textInputChannel = nil;
-  _undoManagerChannel.reset();
+  self.undoManagerChannel = nil;
-  _scribbleChannel.reset();
+  self.scribbleChannel = nil;
-  _lifecycleChannel.reset();
+  self.lifecycleChannel = nil;
-  _systemChannel.reset();
+  self.systemChannel = nil;
-  _settingsChannel.reset();
+  self.settingsChannel = nil;
-  _keyEventChannel.reset();
+  self.keyEventChannel = nil;
-  _spellCheckChannel.reset();
+  self.spellCheckChannel = nil;
 }
 
 - (void)startProfiler {
   FML_DCHECK(!_threadHost->name_prefix.empty());
   _profiler_metrics = std::make_shared<flutter::ProfilerMetricsIOS>();
+  __weak FlutterEngine* weakSelf = self;
   _profiler = std::make_shared<flutter::SamplingProfiler>(
       _threadHost->name_prefix.c_str(), _threadHost->profiler_thread->GetTaskRunner(),
-      [self]() { return self->_profiler_metrics->GenerateSample(); }, kNumProfilerSamplesPerSec);
+      [weakSelf]() {
+        FlutterEngine* strongSelf = weakSelf;
+        return strongSelf ? strongSelf->_profiler_metrics->GenerateSample()
+                          : flutter::ProfileSample{};
+      },
+      kNumProfilerSamplesPerSec);
   _profiler->Start();
 }
 
@@ -583,165 +523,155 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
 - (void)setUpChannels {
   // This will be invoked once the shell is done setting up and the isolate ID
   // for the UI isolate is available.
-  fml::WeakNSObject<FlutterEngine> weakSelf = [self getWeakNSObject];
+  __weak FlutterEngine* weakSelf = self;
   [_binaryMessenger setMessageHandlerOnChannel:@"flutter/isolate"
                           binaryMessageHandler:^(NSData* message, FlutterBinaryReply reply) {
                             if (weakSelf) {
-                              weakSelf.get().isolateId =
+                              weakSelf.isolateId =
                                   [[FlutterStringCodec sharedInstance] decode:message];
                             }
                           }];
 
-  _localizationChannel.reset([[FlutterMethodChannel alloc]
+  self.localizationChannel =
-         initWithName:@"flutter/localization"
+      [[FlutterMethodChannel alloc] initWithName:@"flutter/localization"
-      binaryMessenger:self.binaryMessenger
+                                 binaryMessenger:self.binaryMessenger
-                codec:[FlutterJSONMethodCodec sharedInstance]]);
+                                           codec:[FlutterJSONMethodCodec sharedInstance]];
 
-  _navigationChannel.reset([[FlutterMethodChannel alloc]
+  self.navigationChannel =
-         initWithName:@"flutter/navigation"
+      [[FlutterMethodChannel alloc] initWithName:@"flutter/navigation"
-      binaryMessenger:self.binaryMessenger
+                                 binaryMessenger:self.binaryMessenger
-                codec:[FlutterJSONMethodCodec sharedInstance]]);
+                                           codec:[FlutterJSONMethodCodec sharedInstance]];
 
   if ([_initialRoute length] > 0) {
     // Flutter isn't ready to receive this method call yet but the channel buffer will cache this.
-    [_navigationChannel invokeMethod:@"setInitialRoute" arguments:_initialRoute];
+    [self.navigationChannel invokeMethod:@"setInitialRoute" arguments:_initialRoute];
-    [_initialRoute release];
     _initialRoute = nil;
   }
 
-  _restorationChannel.reset([[FlutterMethodChannel alloc]
+  self.restorationChannel =
-         initWithName:@"flutter/restoration"
+      [[FlutterMethodChannel alloc] initWithName:@"flutter/restoration"
-      binaryMessenger:self.binaryMessenger
+                                 binaryMessenger:self.binaryMessenger
-                codec:[FlutterStandardMethodCodec sharedInstance]]);
+                                           codec:[FlutterStandardMethodCodec sharedInstance]];
 
-  _platformChannel.reset([[FlutterMethodChannel alloc]
+  self.platformChannel =
-         initWithName:@"flutter/platform"
+      [[FlutterMethodChannel alloc] initWithName:@"flutter/platform"
-      binaryMessenger:self.binaryMessenger
+                                 binaryMessenger:self.binaryMessenger
-                codec:[FlutterJSONMethodCodec sharedInstance]]);
+                                           codec:[FlutterJSONMethodCodec sharedInstance]];
 
-  _platformViewsChannel.reset([[FlutterMethodChannel alloc]
+  self.platformViewsChannel =
-         initWithName:@"flutter/platform_views"
+      [[FlutterMethodChannel alloc] initWithName:@"flutter/platform_views"
-      binaryMessenger:self.binaryMessenger
+                                 binaryMessenger:self.binaryMessenger
-                codec:[FlutterStandardMethodCodec sharedInstance]]);
+                                           codec:[FlutterStandardMethodCodec sharedInstance]];
 
-  _textInputChannel.reset([[FlutterMethodChannel alloc]
+  self.textInputChannel =
-         initWithName:@"flutter/textinput"
+      [[FlutterMethodChannel alloc] initWithName:@"flutter/textinput"
-      binaryMessenger:self.binaryMessenger
+                                 binaryMessenger:self.binaryMessenger
-                codec:[FlutterJSONMethodCodec sharedInstance]]);
+                                           codec:[FlutterJSONMethodCodec sharedInstance]];
 
-  _undoManagerChannel.reset([[FlutterMethodChannel alloc]
+  self.undoManagerChannel =
-         initWithName:@"flutter/undomanager"
+      [[FlutterMethodChannel alloc] initWithName:@"flutter/undomanager"
-      binaryMessenger:self.binaryMessenger
+                                 binaryMessenger:self.binaryMessenger
-                codec:[FlutterJSONMethodCodec sharedInstance]]);
+                                           codec:[FlutterJSONMethodCodec sharedInstance]];
 
-  _scribbleChannel.reset([[FlutterMethodChannel alloc]
+  self.scribbleChannel =
-         initWithName:@"flutter/scribble"
+      [[FlutterMethodChannel alloc] initWithName:@"flutter/scribble"
-      binaryMessenger:self.binaryMessenger
+                                 binaryMessenger:self.binaryMessenger
-                codec:[FlutterJSONMethodCodec sharedInstance]]);
+                                           codec:[FlutterJSONMethodCodec sharedInstance]];
 
-  _spellCheckChannel.reset([[FlutterMethodChannel alloc]
+  self.spellCheckChannel =
-         initWithName:@"flutter/spellcheck"
+      [[FlutterMethodChannel alloc] initWithName:@"flutter/spellcheck"
-      binaryMessenger:self.binaryMessenger
+                                 binaryMessenger:self.binaryMessenger
-                codec:[FlutterStandardMethodCodec sharedInstance]]);
+                                           codec:[FlutterStandardMethodCodec sharedInstance]];
 
-  _lifecycleChannel.reset([[FlutterBasicMessageChannel alloc]
+  self.lifecycleChannel =
-         initWithName:@"flutter/lifecycle"
+      [[FlutterBasicMessageChannel alloc] initWithName:@"flutter/lifecycle"
-      binaryMessenger:self.binaryMessenger
+                                       binaryMessenger:self.binaryMessenger
-                codec:[FlutterStringCodec sharedInstance]]);
+                                                 codec:[FlutterStringCodec sharedInstance]];
 
-  _systemChannel.reset([[FlutterBasicMessageChannel alloc]
+  self.systemChannel =
-         initWithName:@"flutter/system"
+      [[FlutterBasicMessageChannel alloc] initWithName:@"flutter/system"
-      binaryMessenger:self.binaryMessenger
+                                       binaryMessenger:self.binaryMessenger
-                codec:[FlutterJSONMessageCodec sharedInstance]]);
+                                                 codec:[FlutterJSONMessageCodec sharedInstance]];
 
-  _settingsChannel.reset([[FlutterBasicMessageChannel alloc]
+  self.settingsChannel =
-         initWithName:@"flutter/settings"
+      [[FlutterBasicMessageChannel alloc] initWithName:@"flutter/settings"
-      binaryMessenger:self.binaryMessenger
+                                       binaryMessenger:self.binaryMessenger
-                codec:[FlutterJSONMessageCodec sharedInstance]]);
+                                                 codec:[FlutterJSONMessageCodec sharedInstance]];
 
-  _keyEventChannel.reset([[FlutterBasicMessageChannel alloc]
+  self.keyEventChannel =
-         initWithName:@"flutter/keyevent"
+      [[FlutterBasicMessageChannel alloc] initWithName:@"flutter/keyevent"
-      binaryMessenger:self.binaryMessenger
+                                       binaryMessenger:self.binaryMessenger
-                codec:[FlutterJSONMessageCodec sharedInstance]]);
+                                                 codec:[FlutterJSONMessageCodec sharedInstance]];
 
-  FlutterTextInputPlugin* textInputPlugin = [[FlutterTextInputPlugin alloc] initWithDelegate:self];
+  self.textInputPlugin = [[FlutterTextInputPlugin alloc] initWithDelegate:self];
-  _textInputPlugin.reset(textInputPlugin);
+  self.textInputPlugin.indirectScribbleDelegate = self;
-  textInputPlugin.indirectScribbleDelegate = self;
+  [self.textInputPlugin setUpIndirectScribbleInteraction:self.viewController];
-  [textInputPlugin setUpIndirectScribbleInteraction:self.viewController];
 
-  FlutterUndoManagerPlugin* undoManagerPlugin =
+  self.undoManagerPlugin = [[FlutterUndoManagerPlugin alloc] initWithDelegate:self];
-      [[FlutterUndoManagerPlugin alloc] initWithDelegate:self];
+  self.platformPlugin = [[FlutterPlatformPlugin alloc] initWithEngine:self];
-  _undoManagerPlugin.reset(undoManagerPlugin);
 
-  _platformPlugin.reset([[FlutterPlatformPlugin alloc] initWithEngine:[self getWeakNSObject]]);
+  self.restorationPlugin =
+      [[FlutterRestorationPlugin alloc] initWithChannel:self.restorationChannel
+                                     restorationEnabled:self.restorationEnabled];
+  self.spellCheckPlugin = [[FlutterSpellCheckPlugin alloc] init];
 
-  _restorationPlugin.reset([[FlutterRestorationPlugin alloc]
+  self.screenshotChannel =
-         initWithChannel:_restorationChannel.get()
+      [[FlutterMethodChannel alloc] initWithName:@"flutter/screenshot"
-      restorationEnabled:_restorationEnabled]);
+                                 binaryMessenger:self.binaryMessenger
-  _spellCheckPlugin.reset([[FlutterSpellCheckPlugin alloc] init]);
+                                           codec:[FlutterStandardMethodCodec sharedInstance]];
 
-  _screenshotChannel.reset([[FlutterMethodChannel alloc]
+  [self.screenshotChannel setMethodCallHandler:^(FlutterMethodCall* _Nonnull call,
-         initWithName:@"flutter/screenshot"
+                                                 FlutterResult _Nonnull result) {
-      binaryMessenger:self.binaryMessenger
+    FlutterEngine* strongSelf = weakSelf;
-                codec:[FlutterStandardMethodCodec sharedInstance]]);
+    if (!(strongSelf && strongSelf->_shell && strongSelf->_shell->IsSetup())) {
-
+      return result([FlutterError
-  [_screenshotChannel.get()
+          errorWithCode:@"invalid_state"
-      setMethodCallHandler:^(FlutterMethodCall* _Nonnull call, FlutterResult _Nonnull result) {
+                message:@"Requesting screenshot while engine is not running."
-        if (!(weakSelf.get() && weakSelf.get()->_shell && weakSelf.get()->_shell->IsSetup())) {
+                details:nil]);
-          return result([FlutterError
+    }
-              errorWithCode:@"invalid_state"
+    flutter::Rasterizer::Screenshot screenshot =
-                    message:@"Requesting screenshot while engine is not running."
+        [strongSelf screenshot:flutter::Rasterizer::ScreenshotType::SurfaceData base64Encode:NO];
-                    details:nil]);
+    if (!screenshot.data) {
-        }
+      return result([FlutterError errorWithCode:@"failure"
-        flutter::Rasterizer::Screenshot screenshot =
+                                        message:@"Unable to get screenshot."
-            [weakSelf.get() screenshot:flutter::Rasterizer::ScreenshotType::SurfaceData
+                                        details:nil]);
-                          base64Encode:NO];
+    }
-        if (!screenshot.data) {
+    // TODO(gaaclarke): Find way to eliminate this data copy.
-          return result([FlutterError errorWithCode:@"failure"
+    NSData* data = [NSData dataWithBytes:screenshot.data->writable_data()
-                                            message:@"Unable to get screenshot."
+                                  length:screenshot.data->size()];
-                                            details:nil]);
+    NSString* format = [NSString stringWithUTF8String:screenshot.format.c_str()];
-        }
+    NSNumber* width = @(screenshot.frame_size.fWidth);
-        // TODO(gaaclarke): Find way to eliminate this data copy.
+    NSNumber* height = @(screenshot.frame_size.fHeight);
-        NSData* data = [NSData dataWithBytes:screenshot.data->writable_data()
+    return result(@[ width, height, format ?: [NSNull null], data ]);
-                                      length:screenshot.data->size()];
+  }];
-        NSString* format = [NSString stringWithUTF8String:screenshot.format.c_str()];
-        NSNumber* width = @(screenshot.frame_size.fWidth);
-        NSNumber* height = @(screenshot.frame_size.fHeight);
-        return result(@[ width, height, format ?: [NSNull null], data ]);
-      }];
 }
 
 - (void)maybeSetupPlatformViewChannels {
   if (_shell && self.shell.IsSetup()) {
-    FlutterPlatformPlugin* platformPlugin = _platformPlugin.get();
+    __weak FlutterEngine* weakSelf = self;
-    [_platformChannel.get() setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
+
-      [platformPlugin handleMethodCall:call result:result];
+    [self.platformChannel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
+      [weakSelf.platformPlugin handleMethodCall:call result:result];
     }];
 
-    fml::WeakNSObject<FlutterEngine> weakSelf = [self getWeakNSObject];
+    [self.platformViewsChannel
-    [_platformViewsChannel.get()
         setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
           if (weakSelf) {
-            weakSelf.get().platformViewsController->OnMethodCall(call, result);
+            weakSelf.platformViewsController->OnMethodCall(call, result);
           }
         }];
 
-    FlutterTextInputPlugin* textInputPlugin = _textInputPlugin.get();
+    [self.textInputChannel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
-    [_textInputChannel.get() setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
+      [weakSelf.textInputPlugin handleMethodCall:call result:result];
-      [textInputPlugin handleMethodCall:call result:result];
     }];
 
-    FlutterUndoManagerPlugin* undoManagerPlugin = _undoManagerPlugin.get();
+    [self.undoManagerChannel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
-    [_undoManagerChannel.get()
+      [weakSelf.undoManagerPlugin handleMethodCall:call result:result];
-        setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
+    }];
-          [undoManagerPlugin handleMethodCall:call result:result];
-        }];
 
-    FlutterSpellCheckPlugin* spellCheckPlugin = _spellCheckPlugin.get();
+    [self.spellCheckChannel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
-    [_spellCheckChannel.get()
+      [weakSelf.spellCheckPlugin handleMethodCall:call result:result];
-        setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
+    }];
-          [spellCheckPlugin handleMethodCall:call result:result];
-        }];
   }
 }
 
@@ -754,9 +684,9 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
           libraryURI:(NSString*)libraryOrNil
       entrypointArgs:(NSArray<NSString*>*)entrypointArgs {
   // Launch the Dart application with the inferred run configuration.
-  self.shell.RunEngine([_dartProject.get() runConfigurationForEntrypoint:entrypoint
+  self.shell.RunEngine([self.dartProject runConfigurationForEntrypoint:entrypoint
-                                                            libraryOrNil:libraryOrNil
+                                                          libraryOrNil:libraryOrNil
-                                                          entrypointArgs:entrypointArgs]);
+                                                        entrypointArgs:entrypointArgs]);
 }
 
 - (void)setUpShell:(std::unique_ptr<flutter::Shell>)shell
@@ -765,8 +695,8 @@ static constexpr int kNumProfilerSamplesPerSec = 5;
   [self setUpChannels];
   [self onLocaleUpdated:nil];
   [self updateDisplays];
-  _publisher.reset([[FlutterDartVMServicePublisher alloc]
+  self.publisher = [[FlutterDartVMServicePublisher alloc]
-      initWithEnableVMServicePublication:doesVMServicePublication]);
+      initWithEnableVMServicePublication:doesVMServicePublication];
   [self maybeSetupPlatformViewChannels];
   _shell->SetGpuAvailability(_isGpuDisabled ? flutter::GpuAvailability::kUnavailable
                                             : flutter::GpuAvailability::kAvailable);
@@ -845,7 +775,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
 
   self.initialRoute = initialRoute;
 
-  auto settings = [_dartProject.get() settings];
+  auto settings = [self.dartProject settings];
   if (initialRoute != nil) {
     self.initialRoute = initialRoute;
   } else if (settings.route.empty() == false) {
@@ -854,24 +784,28 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
 
   FlutterView.forceSoftwareRendering = settings.enable_software_rendering;
 
-  auto platformData = [_dartProject.get() defaultPlatformData];
+  auto platformData = [self.dartProject defaultPlatformData];
 
   SetEntryPoint(&settings, entrypoint, libraryURI);
 
-  NSString* threadLabel = [FlutterEngine generateThreadLabel:_labelPrefix];
+  NSString* threadLabel = [FlutterEngine generateThreadLabel:self.labelPrefix];
   _threadHost = std::make_shared<flutter::ThreadHost>();
   *_threadHost = MakeThreadHost(threadLabel, settings);
 
-  // Lambda captures by pointers to ObjC objects are fine here because the
+  __weak FlutterEngine* weakSelf = self;
-  // create call is synchronous.
   flutter::Shell::CreateCallback<flutter::PlatformView> on_create_platform_view =
-      [self](flutter::Shell& shell) {
+      [weakSelf](flutter::Shell& shell) {
-        [self recreatePlatformViewController];
+        FlutterEngine* strongSelf = weakSelf;
-        self->_platformViewsController->SetTaskRunner(
+        if (!strongSelf) {
+          return std::unique_ptr<flutter::PlatformViewIOS>();
+        }
+        [strongSelf recreatePlatformViewController];
+        strongSelf->_platformViewsController->SetTaskRunner(
             shell.GetTaskRunners().GetPlatformTaskRunner());
         return std::make_unique<flutter::PlatformViewIOS>(
-            shell, self->_renderingApi, self->_platformViewsController, shell.GetTaskRunners(),
+            shell, strongSelf->_renderingApi, strongSelf->_platformViewsController,
-            shell.GetConcurrentWorkerTaskRunner(), shell.GetIsGpuDisabledSyncSwitch());
+            shell.GetTaskRunners(), shell.GetConcurrentWorkerTaskRunner(),
+            shell.GetIsGpuDisabledSyncSwitch());
       };
 
   flutter::Shell::CreateCallback<flutter::Rasterizer> on_create_rasterizer =
@@ -988,7 +922,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   if (_shell) {
     _shell->NotifyLowMemoryWarning();
   }
-  [_systemChannel sendMessage:@{@"type" : @"memoryPressure"}];
+  [self.systemChannel sendMessage:@{@"type" : @"memoryPressure"}];
 }
 
 #pragma mark - Text input delegate
@@ -996,23 +930,23 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
          updateEditingClient:(int)client
                    withState:(NSDictionary*)state {
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.updateEditingState"
+  [self.textInputChannel invokeMethod:@"TextInputClient.updateEditingState"
-                              arguments:@[ @(client), state ]];
+                            arguments:@[ @(client), state ]];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
          updateEditingClient:(int)client
                    withState:(NSDictionary*)state
                      withTag:(NSString*)tag {
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.updateEditingStateWithTag"
+  [self.textInputChannel invokeMethod:@"TextInputClient.updateEditingStateWithTag"
-                              arguments:@[ @(client), @{tag : state} ]];
+                            arguments:@[ @(client), @{tag : state} ]];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
          updateEditingClient:(int)client
                    withDelta:(NSDictionary*)delta {
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.updateEditingStateWithDeltas"
+  [self.textInputChannel invokeMethod:@"TextInputClient.updateEditingStateWithDeltas"
-                              arguments:@[ @(client), delta ]];
+                            arguments:@[ @(client), delta ]];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
@@ -1031,8 +965,8 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
       stateString = @"FloatingCursorDragState.end";
       break;
   }
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.updateFloatingCursor"
+  [self.textInputChannel invokeMethod:@"TextInputClient.updateFloatingCursor"
-                              arguments:@[ @(client), stateString, position ]];
+                            arguments:@[ @(client), stateString, position ]];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
@@ -1078,22 +1012,22 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
       actionString = @"TextInputAction.newline";
       break;
   }
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.performAction"
+  [self.textInputChannel invokeMethod:@"TextInputClient.performAction"
-                              arguments:@[ @(client), actionString ]];
+                            arguments:@[ @(client), actionString ]];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
     showAutocorrectionPromptRectForStart:(NSUInteger)start
                                      end:(NSUInteger)end
                               withClient:(int)client {
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.showAutocorrectionPromptRect"
+  [self.textInputChannel invokeMethod:@"TextInputClient.showAutocorrectionPromptRect"
-                              arguments:@[ @(client), @(start), @(end) ]];
+                            arguments:@[ @(client), @(start), @(end) ]];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
     willDismissEditMenuWithTextInputClient:(int)client {
-  [_platformChannel.get() invokeMethod:@"ContextMenu.onDismissSystemContextMenu"
+  [self.platformChannel invokeMethod:@"ContextMenu.onDismissSystemContextMenu"
-                             arguments:@[ @(client) ]];
+                           arguments:@[ @(client) ]];
 }
 
 #pragma mark - FlutterViewEngineDelegate
@@ -1102,7 +1036,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
   // the framework has finished transitioning to the Scribble channel.
   // https://github.com/flutter/flutter/pull/115296
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.showToolbar" arguments:@[ @(client) ]];
+  [self.textInputChannel invokeMethod:@"TextInputClient.showToolbar" arguments:@[ @(client) ]];
 }
 
 - (void)flutterTextInputPlugin:(FlutterTextInputPlugin*)textInputPlugin
@@ -1112,7 +1046,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
   // the framework has finished transitioning to the Scribble channel.
   // https://github.com/flutter/flutter/pull/115296
-  [_textInputChannel.get()
+  [self.textInputChannel
       invokeMethod:@"TextInputClient.focusElement"
          arguments:@[ elementIdentifier, @(referencePoint.x), @(referencePoint.y) ]
             result:callback];
@@ -1124,7 +1058,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
   // the framework has finished transitioning to the Scribble channel.
   // https://github.com/flutter/flutter/pull/115296
-  [_textInputChannel.get()
+  [self.textInputChannel
       invokeMethod:@"TextInputClient.requestElementsInRect"
          arguments:@[ @(rect.origin.x), @(rect.origin.y), @(rect.size.width), @(rect.size.height) ]
             result:callback];
@@ -1134,15 +1068,14 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
   // the framework has finished transitioning to the Scribble channel.
   // https://github.com/flutter/flutter/pull/115296
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.scribbleInteractionBegan" arguments:nil];
+  [self.textInputChannel invokeMethod:@"TextInputClient.scribbleInteractionBegan" arguments:nil];
 }
 
 - (void)flutterTextInputViewScribbleInteractionFinished:(FlutterTextInputView*)textInputView {
   // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
   // the framework has finished transitioning to the Scribble channel.
   // https://github.com/flutter/flutter/pull/115296
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.scribbleInteractionFinished"
+  [self.textInputChannel invokeMethod:@"TextInputClient.scribbleInteractionFinished" arguments:nil];
-                              arguments:nil];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
@@ -1151,8 +1084,8 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
   // the framework has finished transitioning to the Scribble channel.
   // https://github.com/flutter/flutter/pull/115296
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.insertTextPlaceholder"
+  [self.textInputChannel invokeMethod:@"TextInputClient.insertTextPlaceholder"
-                              arguments:@[ @(client), @(size.width), @(size.height) ]];
+                            arguments:@[ @(client), @(size.width), @(size.height) ]];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
@@ -1160,8 +1093,8 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
   // the framework has finished transitioning to the Scribble channel.
   // https://github.com/flutter/flutter/pull/115296
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.removeTextPlaceholder"
+  [self.textInputChannel invokeMethod:@"TextInputClient.removeTextPlaceholder"
-                              arguments:@[ @(client) ]];
+                            arguments:@[ @(client) ]];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
@@ -1169,8 +1102,8 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   // When flutter text input view resign first responder, send a message to
   // framework to ensure the focus state is correct. This is useful when close
   // keyboard from platform side.
-  [_textInputChannel.get() invokeMethod:@"TextInputClient.onConnectionClosed"
+  [self.textInputChannel invokeMethod:@"TextInputClient.onConnectionClosed"
-                              arguments:@[ @(client) ]];
+                            arguments:@[ @(client) ]];
 
   // Platform view's first responder detection logic:
   //
@@ -1197,7 +1130,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
       return;
     }
 
-    [_platformViewsChannel.get() invokeMethod:@"viewFocused" arguments:@(platform_view_id)];
+    [self.platformViewsChannel invokeMethod:@"viewFocused" arguments:@(platform_view_id)];
   });
 }
 
@@ -1205,7 +1138,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
 
 - (void)handleUndoWithDirection:(FlutterUndoRedoDirection)direction {
   NSString* action = (direction == FlutterUndoRedoDirectionUndo) ? @"undo" : @"redo";
-  [_undoManagerChannel.get() invokeMethod:@"UndoManagerClient.handleUndo" arguments:@[ action ]];
+  [self.undoManagerChannel invokeMethod:@"UndoManagerClient.handleUndo" arguments:@[ action ]];
 }
 
 - (UIView<UITextInput>*)activeTextInputView {
@@ -1244,8 +1177,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   // Discard the previous messenger and keep the new one.
   if (binaryMessenger != _binaryMessenger) {
     _binaryMessenger.parent = nil;
-    [_binaryMessenger release];
+    _binaryMessenger = binaryMessenger;
-    _binaryMessenger = [binaryMessenger retain];
   }
 }
 
@@ -1317,7 +1249,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
 #pragma mark - FlutterTextureRegistry
 
 - (int64_t)registerTexture:(NSObject<FlutterTexture>*)texture {
-  int64_t textureId = _nextTextureId++;
+  int64_t textureId = self.nextTextureId++;
   self.iosPlatformView->RegisterExternalTexture(textureId, texture);
   return textureId;
 }
@@ -1350,7 +1282,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   FlutterEngineRegistrar* result = [[FlutterEngineRegistrar alloc] initWithPlugin:pluginKey
                                                                     flutterEngine:self];
   self.registrars[pluginKey] = result;
-  return [result autorelease];
+  return result;
 }
 
 - (BOOL)hasPlugin:(NSString*)pluginKey {
@@ -1406,10 +1338,10 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
 
 - (void)onLocaleUpdated:(NSNotification*)notification {
   // Get and pass the user's preferred locale list to dart:ui.
-  NSMutableArray<NSString*>* localeData = [[[NSMutableArray alloc] init] autorelease];
+  NSMutableArray<NSString*>* localeData = [[NSMutableArray alloc] init];
   NSArray<NSString*>* preferredLocales = [NSLocale preferredLanguages];
   for (NSString* localeID in preferredLocales) {
-    NSLocale* locale = [[[NSLocale alloc] initWithLocaleIdentifier:localeID] autorelease];
+    NSLocale* locale = [[NSLocale alloc] initWithLocaleIdentifier:localeID];
     NSString* languageCode = [locale objectForKey:NSLocaleLanguageCode];
     NSString* countryCode = [locale objectForKey:NSLocaleCountryCode];
     NSString* scriptCode = [locale objectForKey:NSLocaleScriptCode];
@@ -1446,13 +1378,13 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
                          initialRoute:(/*nullable*/ NSString*)initialRoute
                        entrypointArgs:(/*nullable*/ NSArray<NSString*>*)entrypointArgs {
   NSAssert(_shell, @"Spawning from an engine without a shell (possibly not run).");
-  FlutterEngine* result = [[FlutterEngine alloc] initWithName:_labelPrefix
+  FlutterEngine* result = [[FlutterEngine alloc] initWithName:self.labelPrefix
-                                                      project:_dartProject.get()
+                                                      project:self.dartProject
-                                       allowHeadlessExecution:_allowHeadlessExecution];
+                                       allowHeadlessExecution:self.allowHeadlessExecution];
   flutter::RunConfiguration configuration =
-      [_dartProject.get() runConfigurationForEntrypoint:entrypoint
+      [self.dartProject runConfigurationForEntrypoint:entrypoint
-                                           libraryOrNil:libraryURI
+                                         libraryOrNil:libraryURI
-                                         entrypointArgs:entrypointArgs];
+                                       entrypointArgs:entrypointArgs];
 
   fml::WeakPtr<flutter::PlatformView> platform_view = _shell->GetPlatformView();
   FML_DCHECK(platform_view);
@@ -1489,7 +1421,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   result->_profiler_metrics = _profiler_metrics;
   result->_isGpuDisabled = _isGpuDisabled;
   [result setUpShell:std::move(shell) withVMServicePublication:NO];
-  return [result autorelease];
+  return result;
 }
 
 - (const flutter::ThreadHost&)threadHost {
@@ -1497,7 +1429,7 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
 }
 
 - (FlutterDartProject*)project {
-  return _dartProject.get();
+  return self.dartProject;
 }
 
 - (BOOL)isUsingImpeller {
@@ -1518,11 +1450,6 @@ static void SetEntryPoint(flutter::Settings* settings, NSString* entrypoint, NSS
   return self;
 }
 
-- (void)dealloc {
-  [_pluginKey release];
-  [super dealloc];
-}
-
 - (NSObject<FlutterBinaryMessenger>*)messenger {
   return _flutterEngine.binaryMessenger;
 }

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformPlugin.h

@@ -12,7 +12,7 @@
 @interface FlutterPlatformPlugin : NSObject
 - (instancetype)init NS_UNAVAILABLE;
 + (instancetype)new NS_UNAVAILABLE;
-- (instancetype)initWithEngine:(fml::WeakNSObject<FlutterEngine>)engine NS_DESIGNATED_INITIALIZER;
+- (instancetype)initWithEngine:(FlutterEngine*)engine NS_DESIGNATED_INITIALIZER;
 - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result;
 
 @end

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformPlugin.mm

@@ -82,7 +82,7 @@ static void SetStatusBarStyleForSharedApplication(UIStatusBarStyle style) {
 
 @implementation FlutterPlatformPlugin
 
-- (instancetype)initWithEngine:(fml::WeakNSObject<FlutterEngine>)engine {
+- (instancetype)initWithEngine:(FlutterEngine*)engine {
   FML_DCHECK(engine) << "engine must be set";
   self = [super init];
 

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformPluginTest.mm

@@ -37,15 +37,12 @@ FLUTTER_ASSERT_ARC
   OCMStub([mockApplication sharedApplication]).andReturn(mockApplication);
 
   FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test" project:nil];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
   [engine runWithEntrypoint:nil];
 
   XCTestExpectation* invokeExpectation =
       [self expectationWithDescription:@"Web search launched with escaped search term"];
 
-  FlutterPlatformPlugin* plugin =
+  FlutterPlatformPlugin* plugin = [[FlutterPlatformPlugin alloc] initWithEngine:engine];
-      [[FlutterPlatformPlugin alloc] initWithEngine:_weakFactory->GetWeakNSObject()];
   FlutterPlatformPlugin* mockPlugin = OCMPartialMock(plugin);
 
   FlutterMethodCall* methodCall = [FlutterMethodCall methodCallWithMethodName:@"SearchWeb.invoke"
@@ -71,15 +68,12 @@ FLUTTER_ASSERT_ARC
   OCMStub([mockApplication sharedApplication]).andReturn(mockApplication);
 
   FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test" project:nil];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
   [engine runWithEntrypoint:nil];
 
   XCTestExpectation* invokeExpectation =
       [self expectationWithDescription:@"Web search launched with non escaped search term"];
 
-  FlutterPlatformPlugin* plugin =
+  FlutterPlatformPlugin* plugin = [[FlutterPlatformPlugin alloc] initWithEngine:engine];
-      [[FlutterPlatformPlugin alloc] initWithEngine:_weakFactory->GetWeakNSObject()];
   FlutterPlatformPlugin* mockPlugin = OCMPartialMock(plugin);
 
   FlutterMethodCall* methodCall = [FlutterMethodCall methodCallWithMethodName:@"SearchWeb.invoke"
@@ -103,8 +97,6 @@ FLUTTER_ASSERT_ARC
 - (void)testLookUpCallInitiated {
   FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test" project:nil];
   [engine runWithEntrypoint:nil];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
 
   XCTestExpectation* presentExpectation =
       [self expectationWithDescription:@"Look Up view controller presented"];
@@ -114,8 +106,7 @@ FLUTTER_ASSERT_ARC
                                                                                        bundle:nil];
   FlutterViewController* mockEngineViewController = OCMPartialMock(engineViewController);
 
-  FlutterPlatformPlugin* plugin =
+  FlutterPlatformPlugin* plugin = [[FlutterPlatformPlugin alloc] initWithEngine:engine];
-      [[FlutterPlatformPlugin alloc] initWithEngine:_weakFactory->GetWeakNSObject()];
   FlutterPlatformPlugin* mockPlugin = OCMPartialMock(plugin);
 
   FlutterMethodCall* methodCall = [FlutterMethodCall methodCallWithMethodName:@"LookUp.invoke"
@@ -134,8 +125,6 @@ FLUTTER_ASSERT_ARC
 - (void)testShareScreenInvoked {
   FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test" project:nil];
   [engine runWithEntrypoint:nil];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
 
   XCTestExpectation* presentExpectation =
       [self expectationWithDescription:@"Share view controller presented"];
@@ -149,8 +138,7 @@ FLUTTER_ASSERT_ARC
                    animated:YES
                  completion:nil]);
 
-  FlutterPlatformPlugin* plugin =
+  FlutterPlatformPlugin* plugin = [[FlutterPlatformPlugin alloc] initWithEngine:engine];
-      [[FlutterPlatformPlugin alloc] initWithEngine:_weakFactory->GetWeakNSObject()];
   FlutterPlatformPlugin* mockPlugin = OCMPartialMock(plugin);
 
   FlutterMethodCall* methodCall = [FlutterMethodCall methodCallWithMethodName:@"Share.invoke"
@@ -169,8 +157,6 @@ FLUTTER_ASSERT_ARC
 - (void)testShareScreenInvokedOnIPad {
   FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test" project:nil];
   [engine runWithEntrypoint:nil];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
 
   XCTestExpectation* presentExpectation =
       [self expectationWithDescription:@"Share view controller presented on iPad"];
@@ -187,8 +173,7 @@ FLUTTER_ASSERT_ARC
   id mockTraitCollection = OCMClassMock([UITraitCollection class]);
   OCMStub([mockTraitCollection userInterfaceIdiom]).andReturn(UIUserInterfaceIdiomPad);
 
-  FlutterPlatformPlugin* plugin =
+  FlutterPlatformPlugin* plugin = [[FlutterPlatformPlugin alloc] initWithEngine:engine];
-      [[FlutterPlatformPlugin alloc] initWithEngine:_weakFactory->GetWeakNSObject()];
   FlutterPlatformPlugin* mockPlugin = OCMPartialMock(plugin);
 
   FlutterMethodCall* methodCall = [FlutterMethodCall methodCallWithMethodName:@"Share.invoke"
@@ -207,10 +192,7 @@ FLUTTER_ASSERT_ARC
 - (void)testClipboardHasCorrectStrings {
   [UIPasteboard generalPasteboard].string = nil;
   FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test" project:nil];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
+  FlutterPlatformPlugin* plugin = [[FlutterPlatformPlugin alloc] initWithEngine:engine];
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
-  FlutterPlatformPlugin* plugin =
-      [[FlutterPlatformPlugin alloc] initWithEngine:_weakFactory->GetWeakNSObject()];
 
   XCTestExpectation* setStringExpectation = [self expectationWithDescription:@"setString"];
   FlutterResult resultSet = ^(id result) {
@@ -246,10 +228,7 @@ FLUTTER_ASSERT_ARC
 - (void)testClipboardSetDataToNullDoNotCrash {
   [UIPasteboard generalPasteboard].string = nil;
   FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test" project:nil];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
+  FlutterPlatformPlugin* plugin = [[FlutterPlatformPlugin alloc] initWithEngine:engine];
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
-  FlutterPlatformPlugin* plugin =
-      [[FlutterPlatformPlugin alloc] initWithEngine:_weakFactory->GetWeakNSObject()];
 
   XCTestExpectation* setStringExpectation = [self expectationWithDescription:@"setData"];
   FlutterResult resultSet = ^(id result) {
@@ -280,10 +259,7 @@ FLUTTER_ASSERT_ARC
       [[UINavigationController alloc] initWithRootViewController:flutterViewController];
   UITabBarController* tabBarController = [[UITabBarController alloc] init];
   tabBarController.viewControllers = @[ navigationController ];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
+  FlutterPlatformPlugin* plugin = [[FlutterPlatformPlugin alloc] initWithEngine:engine];
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
-  FlutterPlatformPlugin* plugin =
-      [[FlutterPlatformPlugin alloc] initWithEngine:_weakFactory->GetWeakNSObject()];
 
   id navigationControllerMock = OCMPartialMock(navigationController);
   OCMStub([navigationControllerMock popViewControllerAnimated:YES]);
@@ -303,12 +279,9 @@ FLUTTER_ASSERT_ARC
 
 - (void)testWhetherDeviceHasLiveTextInputInvokeCorrectly {
   FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test" project:nil];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
   XCTestExpectation* invokeExpectation =
       [self expectationWithDescription:@"isLiveTextInputAvailableInvoke"];
-  FlutterPlatformPlugin* plugin =
+  FlutterPlatformPlugin* plugin = [[FlutterPlatformPlugin alloc] initWithEngine:engine];
-      [[FlutterPlatformPlugin alloc] initWithEngine:_weakFactory->GetWeakNSObject()];
   FlutterPlatformPlugin* mockPlugin = OCMPartialMock(plugin);
   FlutterMethodCall* methodCall =
       [FlutterMethodCall methodCallWithMethodName:@"LiveText.isLiveTextInputAvailable"
@@ -331,8 +304,6 @@ FLUTTER_ASSERT_ARC
     [engine runWithEntrypoint:nil];
     FlutterViewController* flutterViewController =
         [[FlutterViewController alloc] initWithEngine:engine nibName:nil bundle:nil];
-    std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
-        std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
     XCTAssertFalse(flutterViewController.prefersStatusBarHidden);
 
     // Update to hidden.
@@ -371,8 +342,6 @@ FLUTTER_ASSERT_ARC
     [engine runWithEntrypoint:nil];
     FlutterViewController* flutterViewController =
         [[FlutterViewController alloc] initWithEngine:engine nibName:nil bundle:nil];
-    std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
-        std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
     XCTAssertFalse(flutterViewController.prefersStatusBarHidden);
 
     // Update to hidden.
@@ -420,8 +389,6 @@ FLUTTER_ASSERT_ARC
   [engine runWithEntrypoint:nil];
   FlutterViewController* flutterViewController =
       [[FlutterViewController alloc] initWithEngine:engine nibName:nil bundle:nil];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
 
   // Update to hidden.
   FlutterPlatformPlugin* plugin = [engine platformPlugin];
@@ -471,8 +438,6 @@ FLUTTER_ASSERT_ARC
   [engine runWithEntrypoint:nil];
   FlutterViewController* flutterViewController =
       [[FlutterViewController alloc] initWithEngine:engine nibName:nil bundle:nil];
-  std::unique_ptr<fml::WeakNSObjectFactory<FlutterEngine>> _weakFactory =
-      std::make_unique<fml::WeakNSObjectFactory<FlutterEngine>>(engine);
   XCTAssertFalse(flutterViewController.prefersStatusBarHidden);
 
   FlutterPlatformPlugin* plugin = [engine platformPlugin];