From 4833535dccc8e45a9940416091e93db462273aea Mon Sep 17 00:00:00 2001
From: KyleWong <kang.wang1988@gmail.com>
Date: Fri, 11 Oct 2019 00:14:18 +0800
Subject: [PATCH] Fix an objc_overrelease_during_dealloc_error.

---
 shell/platform/darwin/ios/platform_view_ios.h |  3 +-
 .../platform/darwin/ios/platform_view_ios.mm  | 35 +++++++++++++------
 2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/shell/platform/darwin/ios/platform_view_ios.h b/shell/platform/darwin/ios/platform_view_ios.h
index b93379d89a83d..89efebae77cbc 100644
--- a/shell/platform/darwin/ios/platform_view_ios.h
+++ b/shell/platform/darwin/ios/platform_view_ios.h
@@ -46,6 +46,8 @@ class PlatformViewIOS final : public PlatformView {
 
   // |PlatformView|
   void SetSemanticsEnabled(bool enabled) override;
+  
+  void OnFlutterViewControllerDealloced();
 
  private:
   fml::WeakPtr<FlutterViewController> owner_controller_;
@@ -58,7 +60,6 @@ class PlatformViewIOS final : public PlatformView {
   std::unique_ptr<AccessibilityBridge> accessibility_bridge_;
   fml::scoped_nsprotocol<FlutterTextInputPlugin*> text_input_plugin_;
   fml::closure firstFrameCallback_;
-  fml::scoped_nsprotocol<NSObject*> dealloc_view_controller_observer_;
 
   // |PlatformView|
   void HandlePlatformMessage(fml::RefPtr<flutter::PlatformMessage> message) override;
diff --git a/shell/platform/darwin/ios/platform_view_ios.mm b/shell/platform/darwin/ios/platform_view_ios.mm
index af8bbfec1c570..1495731f61dfa 100644
--- a/shell/platform/darwin/ios/platform_view_ios.mm
+++ b/shell/platform/darwin/ios/platform_view_ios.mm
@@ -19,6 +19,10 @@
 
 namespace flutter {
 
+static void notificationHandler(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo) {
+  (static_cast<PlatformViewIOS *>(observer))->OnFlutterViewControllerDealloced();
+}
+
 PlatformViewIOS::PlatformViewIOS(PlatformView::Delegate& delegate,
                                  flutter::TaskRunners task_runners)
     : PlatformView(delegate, std::move(task_runners)) {
@@ -27,7 +31,13 @@
 #endif  // !TARGET_IPHONE_SIMULATOR
 }
 
-PlatformViewIOS::~PlatformViewIOS() = default;
+PlatformViewIOS::~PlatformViewIOS() {
+  CFNotificationCenterRemoveEveryObserver
+  (
+    CFNotificationCenterGetLocalCenter(),
+    this
+  );
+};
 
 PlatformMessageRouter& PlatformViewIOS::GetPlatformMessageRouter() {
   return platform_message_router_;
@@ -54,15 +64,15 @@
 
   // Add an observer that will clear out the owner_controller_ ivar and
   // the accessibility_bridge_ in case the view controller is deleted.
-  dealloc_view_controller_observer_.reset([[NSNotificationCenter defaultCenter]
-      addObserverForName:FlutterViewControllerWillDealloc
-                  object:owner_controller_.get()
-                   queue:[NSOperationQueue mainQueue]
-              usingBlock:^(NSNotification* note) {
-                // Implicit copy of 'this' is fine.
-                accessibility_bridge_.reset();
-                owner_controller_.reset();
-              }]);
+  CFNotificationCenterAddObserver
+  (
+      CFNotificationCenterGetLocalCenter(),
+      this,
+      &notificationHandler,
+      (__bridge CFStringRef)FlutterViewControllerWillDealloc,
+      owner_controller_.get(),
+      CFNotificationSuspensionBehaviorDeliverImmediately
+  );
 
   if (owner_controller_) {
     ios_surface_ =
@@ -81,6 +91,11 @@ new AccessibilityBridge(static_cast<FlutterView*>(owner_controller_.get().view),
   }
 }
 
+void PlatformViewIOS::OnFlutterViewControllerDealloced() {
+    accessibility_bridge_.reset();
+    owner_controller_.reset();
+}
+
 PointerDataDispatcherMaker PlatformViewIOS::GetDispatcherMaker() {
   return [](DefaultPointerDataDispatcher::Delegate& delegate) {
     return std::make_unique<SmoothPointerDataDispatcher>(delegate);