PR comments addressed

src/objective-c/GRPCClient/GRPCCall.h

@@ -183,6 +183,10 @@ extern NSString *const kGRPCTrailersKey;
 - (void)didCloseWithTrailingMetadata:(nullable NSDictionary *)trailingMetadata
                                error:(nullable NSError *)error;
 
+/**
+ * Issued when flow control is enabled for the call and a message written with writeData: method of
+ * GRPCCall2 is passed to gRPC core with SEND_MESSAGE operation.
+ */
 - (void)didWriteData;
 
 @end

src/objective-c/GRPCClient/GRPCCall.m

@@ -680,14 +680,14 @@ const char *kCFStreamVarName = "grpc_cfstream";
     __weak GRPCCall *weakSelf = self;
     [self startReadWithHandler:^(grpc_byte_buffer *message) {
       __strong GRPCCall *strongSelf = weakSelf;
-      if (strongSelf == nil) {
-        grpc_byte_buffer_destroy(message);
-        return;
-      }
       if (message == NULL) {
         // No more messages from the server
         return;
       }
+      if (strongSelf == nil) {
+        grpc_byte_buffer_destroy(message);
+        return;
+      }
       NSData *data = [NSData grpc_dataWithByteBuffer:message];
       grpc_byte_buffer_destroy(message);
       if (!data) {
@@ -696,7 +696,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
         // that's on the hands of any server to have. Instead we finish and ask
         // the server to cancel.
         @synchronized(strongSelf) {
-          strongSelf->_pendingReceiveNextMessages--;
+          strongSelf->_pendingCoreRead = NO;
           [strongSelf
               finishWithError:[NSError errorWithDomain:kGRPCErrorDomain
                                                   code:GRPCErrorCodeResourceExhausted
@@ -872,7 +872,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
     // Response headers received.
     __strong GRPCCall *strongSelf = weakSelf;
     if (strongSelf) {
-      @synchronized(self) {
+      @synchronized(strongSelf) {
         strongSelf.responseHeaders = headers;
         strongSelf->_pendingCoreRead = NO;
         [strongSelf maybeStartNextRead];

src/objective-c/ProtoRPC/ProtoRPC.h

@@ -58,8 +58,9 @@ NS_ASSUME_NONNULL_BEGIN
                                error:(nullable NSError *)error;
 
 /**
- * Issued when a write action is completed. To get a correct flow control behavior, the user of a
- * call should not make more than one writeMessage: call before receiving this callback.
+ * Issued when flow control is enabled for the call and a message (written with writeMessage: method
+ * of GRPCStreamingProtoCall or the initializer of GRPCUnaryProtoCall) is passed to gRPC core with
+ * SEND_MESSAGE operation.
  */
 - (void)didWriteMessage;