Fix race condition in iOS React Native module init (#83)

* Lock in whenInitialized

* Change back setCurrentView to not be within lock scope

* Fix errors

Author: ryantrem

Modules/@babylonjs/react-native/EngineView.tsx

@@ -117,7 +117,7 @@ export const EngineView: FunctionComponent<EngineViewProps> = (props: EngineView
                             snapshotPromise.current = { promise: promise, resolve: resolveFunction };
                         }
                         else {
-                            throw "Resolution functions not initialized after snapshot promise creation.";
+                            throw new Error("Resolution functions not initialized after snapshot promise creation.");
                         }
 
                         UIManager.dispatchViewManagerCommand(
@@ -149,9 +149,14 @@ export const EngineView: FunctionComponent<EngineViewProps> = (props: EngineView
             </View>
         );
     } else {
+        const message = "Could not initialize Babylon Native.";
+        if (!__DEV__) {
+            throw new Error(message);
+        }
+
         return (
             <View style={{flex: 1, justifyContent: 'center', alignItems: 'center'}}>
-                <Text style={{fontSize: 24}}>Could not initialize Babylon Native.</Text>
+                <Text style={{fontSize: 24}}>{message}</Text>
                 { isRemoteDebuggingEnabled && <Text style={{fontSize: 12}}>React Native remote debugging does not work with Babylon Native.</Text> }
             </View>
         );

Modules/@babylonjs/react-native/ios/BabylonNativeInterop.mm

@@ -43,8 +43,7 @@ + (void)setView:(RCTBridge*)bridge jsRunLoop:(NSRunLoop*)jsRunLoop mktView:(MTKV
 
         [jsRunLoop performBlock:^{
             if (bridge != currentBridge) {
-                currentBridge = bridge;
-                [BabylonNativeInterop setCurrentNativeInstance:mtkView width:width height:height];
+                [BabylonNativeInterop setCurrentNativeInstance:bridge mtkView:mtkView width:width height:height];
             } else if (currentNativeInstance) {
                 if (mtkView != currentView) {
                     [BabylonNativeInterop setCurrentView:mtkView];
@@ -104,6 +103,7 @@ + (void)reportTouchEvent:(NSSet<UITouch*>*)touches withEvent:(UIEvent*)event {
 }
 
 + (void)whenInitialized:(RCTBridge*)bridge resolve:(RCTPromiseResolveBlock)resolve {
+    const std::lock_guard<std::mutex> lock(mapMutex);
     if (bridge == currentBridge) {
         resolve([NSNumber numberWithUnsignedLong:reinterpret_cast<uintptr_t>(currentNativeInstance.get())]);
     } else {
@@ -116,16 +116,20 @@ + (void)setCurrentView:(MTKView*)mtkView {
     activeTouches = [NSMutableArray new];
 }
 
-+ (void)setCurrentNativeInstance:(MTKView*)mtkView width:(int)width height:(int)height {
++ (void)setCurrentNativeInstance:(RCTBridge*)bridge mtkView:(MTKView*)mtkView width:(int)width height:(int)height {
     [BabylonNativeInterop setCurrentView:mtkView];
 
-    const std::lock_guard<std::mutex> lock(mapMutex);
+    {
+        const std::lock_guard<std::mutex> lock(mapMutex);
 
-    currentNativeInstance.reset();
+        currentBridge = bridge;
 
-    jsi::Runtime* jsiRuntime = GetJSIRuntime(currentBridge);
-    if (jsiRuntime) {
-        currentNativeInstance = std::make_unique<Babylon::Native>(GetJSIRuntime(currentBridge), (__bridge void*)mtkView, width, height);
+        currentNativeInstance.reset();
+
+        jsi::Runtime* jsiRuntime = GetJSIRuntime(currentBridge);
+        if (jsiRuntime) {
+            currentNativeInstance = std::make_unique<Babylon::Native>(GetJSIRuntime(currentBridge), (__bridge void*)mtkView, width, height);
+        }
     }
 
     auto initializationPromisesIterator = initializationPromises.find((__bridge void*)currentBridge);