Mark const extern

Author: dnfield

shell/platform/darwin/ios/framework/Headers/FlutterViewController.h

@@ -23,7 +23,7 @@
  * The object passed as the sender is the `FlutterViewController` associated
  * with the update.
  */
-const NSNotificationName FlutterSemanticsUpdateNotification = @"FlutterSemanticsUpdate";
+extern NSNotificationName const FlutterSemanticsUpdateNotification;
 
 /**
  * A `UIViewController` implementation for Flutter views.

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -22,6 +22,8 @@
 #include "flutter/shell/platform/darwin/ios/framework/Source/platform_message_response_darwin.h"
 #include "flutter/shell/platform/darwin/ios/platform_view_ios.h"
 
+NSNotificationName const FlutterSemanticsUpdateNotification = @"FlutterSemanticsUpdate";
+
 @implementation FlutterViewController {
   std::unique_ptr<fml::WeakPtrFactory<FlutterViewController>> _weakFactory;
   fml::scoped_nsobject<FlutterEngine> _engine;