diff --git a/React/Base/RCTMultipartDataTask.m b/React/Base/RCTMultipartDataTask.m
index daee3d16d..0fb1623db 100644
--- a/React/Base/RCTMultipartDataTask.m
+++ b/React/Base/RCTMultipartDataTask.m
@@ -57,7 +57,10 @@ static BOOL isStreamTaskSupported() {
   [dataTask resume];
 }
 
-- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler
+- (void)URLSession:(__unused NSURLSession *)session
+          dataTask:(__unused NSURLSessionDataTask *)dataTask
+didReceiveResponse:(NSURLResponse *)response
+ completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler
 {
   if ([response isKindOfClass:[NSHTTPURLResponse class]]) {
     NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
@@ -86,22 +89,25 @@ static BOOL isStreamTaskSupported() {
   completionHandler(NSURLSessionResponseAllow);
 }
 
-- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
+- (void)URLSession:(__unused NSURLSession *)session task:(__unused NSURLSessionTask *)task didCompleteWithError:(NSError *)error
 {
   _partHandler(_statusCode, _headers, _data, error, YES);
 }
 
-- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
+- (void)URLSession:(__unused NSURLSession *)session dataTask:(__unused NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
 {
   [_data appendData:data];
 }
 
-- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didBecomeStreamTask:(NSURLSessionStreamTask *)streamTask
+- (void)URLSession:(__unused NSURLSession *)session dataTask:(__unused NSURLSessionDataTask *)dataTask didBecomeStreamTask:(NSURLSessionStreamTask *)streamTask
 {
   [streamTask captureStreams];
 }
 
-- (void)URLSession:(NSURLSession *)session streamTask:(NSURLSessionStreamTask *)streamTask didBecomeInputStream:(NSInputStream *)inputStream outputStream:(NSOutputStream *)outputStream
+- (void)URLSession:(__unused NSURLSession *)session
+        streamTask:(__unused NSURLSessionStreamTask *)streamTask
+didBecomeInputStream:(NSInputStream *)inputStream
+      outputStream:(__unused NSOutputStream *)outputStream
 {
   RCTMultipartStreamReader *reader = [[RCTMultipartStreamReader alloc] initWithInputStream:inputStream boundary:_boundary];
   RCTMultipartDataTaskCallback partHandler = _partHandler;
diff --git a/React/Modules/RCTDevMenu.m b/React/Modules/RCTDevMenu.m
index f0fc6a296..160e40b92 100644
--- a/React/Modules/RCTDevMenu.m
+++ b/React/Modules/RCTDevMenu.m
@@ -525,8 +525,7 @@ RCT_EXPORT_METHOD(show)
       case RCTDevMenuTypeButton: {
         [_actionSheet addAction:[UIAlertAction actionWithTitle:item.title
                                                          style:UIAlertActionStyleDefault
-                                                       handler:^(UIAlertAction *action) {
-                                                         // Cancel button tappped.
+                                                       handler:^(__unused UIAlertAction *action) {
                                                          [item callHandler];
                                                        }]];
         break;
@@ -535,11 +534,10 @@ RCT_EXPORT_METHOD(show)
         BOOL selected = [item.value boolValue];
         [_actionSheet addAction:[UIAlertAction actionWithTitle:(selected? item.selectedTitle : item.title)
                                                          style:UIAlertActionStyleDefault
-                                                       handler:^(UIAlertAction *action) {
+                                                       handler:^(__unused UIAlertAction *action) {
                                                          BOOL value = [self->_settings[item.key] boolValue];
                                                          [self updateSetting:item.key value:@(!value)]; // will call handler
                                                        }]];
-
         break;
       }
     }
@@ -547,11 +545,10 @@ RCT_EXPORT_METHOD(show)
 
   [_actionSheet addAction:[UIAlertAction actionWithTitle:@"Cancel"
                                                    style:UIAlertActionStyleCancel
-                                                 handler:^(UIAlertAction *action) {
-                                                 }]];
+                                                 handler:nil]];
 
   _presentedItems = items;
-  [RCTPresentedViewController() presentViewController:_actionSheet animated:YES completion:^(void){}];
+  [RCTPresentedViewController() presentViewController:_actionSheet animated:YES completion:nil];
 }
 
 
diff --git a/React/Modules/RCTUIManager.m b/React/Modules/RCTUIManager.m
index 1e35ca958..b1be51732 100644
--- a/React/Modules/RCTUIManager.m
+++ b/React/Modules/RCTUIManager.m
@@ -858,18 +858,21 @@ RCT_EXPORT_METHOD(replaceExistingNonRootView:(nonnull NSNumber *)reactTag
   RCTAssert(shadowView != nil, @"shadowView (for ID %@) not found", reactTag);
 
   RCTShadowView *superShadowView = shadowView.superview;
-  RCTAssert(superShadowView != nil, @"shadowView super (of ID %@) not found", reactTag);
+  if (!superShadowView) {
+    RCTAssert(NO, @"shadowView super (of ID %@) not found", reactTag);
+    return;
+  }
 
   NSUInteger indexOfView = [superShadowView.reactSubviews indexOfObject:shadowView];
   RCTAssert(indexOfView != NSNotFound, @"View's superview doesn't claim it as subview (id %@)", reactTag);
   NSArray<NSNumber *> *removeAtIndices = @[@(indexOfView)];
   NSArray<NSNumber *> *addTags = @[newReactTag];
   [self manageChildren:superShadowView.reactTag
-        moveFromIndices:nil
-          moveToIndices:nil
-      addChildReactTags:addTags
+       moveFromIndices:nil
+         moveToIndices:nil
+     addChildReactTags:addTags
           addAtIndices:removeAtIndices
-        removeAtIndices:removeAtIndices];
+       removeAtIndices:removeAtIndices];
 }
 
 RCT_EXPORT_METHOD(setChildren:(nonnull NSNumber *)containerTag
diff --git a/React/Views/RCTMapManager.m b/React/Views/RCTMapManager.m
index 78fc2f094..875e46c0d 100644
--- a/React/Views/RCTMapManager.m
+++ b/React/Views/RCTMapManager.m
@@ -289,25 +289,19 @@ RCT_CUSTOM_VIEW_PROPERTY(region, MKCoordinateRegion, RCTMap)
   return annotationView;
 }
 
-- (MKOverlayRenderer *)mapView:(__unused MKMapView *)mapView
-            rendererForOverlay:(RCTMapOverlay *)overlay
+- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay
 {
-  if ([overlay isKindOfClass:[RCTMapOverlay class]]) {
-    MKPolylineRenderer *polylineRenderer =
-      [[MKPolylineRenderer alloc] initWithPolyline:overlay];
-    polylineRenderer.strokeColor = overlay.strokeColor;
-    polylineRenderer.lineWidth = overlay.lineWidth;
-    return polylineRenderer;
-  } else {
-    return nil;
-  }
+  RCTAssert([overlay isKindOfClass:[RCTMapOverlay class]], @"Overlay must be of type RCTMapOverlay");
+  MKPolylineRenderer *polylineRenderer = [[MKPolylineRenderer alloc] initWithPolyline:overlay];
+  polylineRenderer.strokeColor = [(RCTMapOverlay *)overlay strokeColor];
+  polylineRenderer.lineWidth = [(RCTMapOverlay *)overlay lineWidth];
+  return polylineRenderer;
 }
 
 - (void)mapView:(RCTMap *)mapView annotationView:(MKAnnotationView *)view
                    calloutAccessoryControlTapped:(UIControl *)control
 {
   if (mapView.onPress) {
-
     // Pass to JS
     RCTMapAnnotation *annotation = (RCTMapAnnotation *)view.annotation;
     mapView.onPress(@{