Remove retain of handler in callbacks and dispatch to dispatchQueue

src/objective-c/GRPCClient/GRPCCall.h

@@ -155,12 +155,16 @@ extern NSString *const kGRPCTrailersKey;
 
 @optional
 
-/** Issued when initial metadata is received from the server. */
+/**
+  * Issued when initial metadata is received from the server. The task must be scheduled onto the
+  * dispatch queue in property \a dispatchQueue.
+  */
 - (void)receivedInitialMetadata:(NSDictionary *_Nullable)initialMetadata;
 
 /**
  * Issued when a message is received from the server. The message is the raw data received from the
- * server, with decompression and without proto deserialization.
+ * server, with decompression and without proto deserialization. The task must be scheduled onto the
+ * dispatch queue in property \a dispatchQueue.
  */
 - (void)receivedRawMessage:(NSData *_Nullable)message;
 
@@ -168,7 +172,8 @@ extern NSString *const kGRPCTrailersKey;
  * Issued when a call finished. If the call finished successfully, \a error is nil and \a
  * trainingMetadata consists any trailing metadata received from the server. Otherwise, \a error
  * is non-nil and contains the corresponding error information, including gRPC error codes and
- * error descriptions.
+ * error descriptions. The task must be scheduled onto the dispatch queue in property
+ * \a dispatchQueue.
  */
 - (void)closedWithTrailingMetadata:(NSDictionary *_Nullable)trailingMetadata
                              error:(NSError *_Nullable)error;

src/objective-c/GRPCClient/GRPCCall.m

@@ -252,30 +252,21 @@ const char *kCFStreamVarName = "grpc_cfstream";
 }
 
 - (void)issueInitialMetadata:(NSDictionary *)initialMetadata {
-  id<GRPCResponseHandler> handler = _handler;
-  if ([handler respondsToSelector:@selector(receivedInitialMetadata:)]) {
-    dispatch_async(handler.dispatchQueue, ^{
-      [handler receivedInitialMetadata:initialMetadata];
-    });
+  if (initialMetadata != nil && [_handler respondsToSelector:@selector(receivedInitialMetadata:)]) {
+    [_handler receivedInitialMetadata:initialMetadata];
   }
 }
 
 - (void)issueMessage:(id)message {
-  id<GRPCResponseHandler> handler = _handler;
-  if ([handler respondsToSelector:@selector(receivedRawMessage:)]) {
-    dispatch_async(handler.dispatchQueue, ^{
-      [handler receivedRawMessage:message];
-    });
+  if (message != nil && [_handler respondsToSelector:@selector(receivedRawMessage:)]) {
+    [_handler receivedRawMessage:message];
   }
 }
 
 - (void)issueClosedWithTrailingMetadata:(NSDictionary *)trailingMetadata error:(NSError *)error {
-  id<GRPCResponseHandler> handler = _handler;
   NSDictionary *trailers = _call.responseTrailers;
-  if ([handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
-    dispatch_async(handler.dispatchQueue, ^{
-      [handler closedWithTrailingMetadata:trailers error:error];
-    });
+  if ([_handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
+    [_handler closedWithTrailingMetadata:trailers error:error];
   }
 }
 

src/objective-c/ProtoRPC/ProtoRPC.h

@@ -30,11 +30,14 @@ NS_ASSUME_NONNULL_BEGIN
 
 @optional
 
-/** Issued when initial metadata is received from the server. */
+/**
+  * Issued when initial metadata is received from the server. The task must be scheduled onto the
+  * dispatch queue in property \a dispatchQueue. */
 - (void)receivedInitialMetadata:(NSDictionary *_Nullable)initialMetadata;
 
 /**
  * Issued when a message is received from the server. The message is the deserialized proto object.
+ * The task must be scheduled onto the dispatch queue in property \a dispatchQueue.
  */
 - (void)receivedProtoMessage:(GPBMessage *_Nullable)message;
 
@@ -42,7 +45,8 @@ NS_ASSUME_NONNULL_BEGIN
  * Issued when a call finished. If the call finished successfully, \a error is nil and \a
  * trainingMetadata consists any trailing metadata received from the server. Otherwise, \a error
  * is non-nil and contains the corresponding error information, including gRPC error codes and
- * error descriptions.
+ * error descriptions. The task must be scheduled onto the dispatch queue in property
+ * \a dispatchQueue.
  */
 - (void)closedWithTrailingMetadata:(NSDictionary *_Nullable)trailingMetadata
                              error:(NSError *_Nullable)error;

src/objective-c/ProtoRPC/ProtoRPC.m

@@ -172,53 +172,44 @@ static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsing
 }
 
 - (void)receivedInitialMetadata:(NSDictionary *_Nullable)initialMetadata {
-  if (_handler && initialMetadata != nil) {
-    id<GRPCProtoResponseHandler> handler = _handler;
-    if ([handler respondsToSelector:@selector(initialMetadata:)]) {
-      dispatch_async(handler.dispatchQueue, ^{
-        [handler receivedInitialMetadata:initialMetadata];
-      });
+  dispatch_async(_dispatchQueue, ^{
+    if (initialMetadata != nil && [self->_handler respondsToSelector:@selector(initialMetadata:)]) {
+      [self->_handler receivedInitialMetadata:initialMetadata];
     }
-  }
+  });
 }
 
 - (void)receivedRawMessage:(NSData *_Nullable)message {
-  if (_handler && message != nil) {
-    id<GRPCProtoResponseHandler> handler = _handler;
-    NSError *error = nil;
-    GPBMessage *parsed = [_responseClass parseFromData:message error:&error];
-    if (parsed) {
-      if ([handler respondsToSelector:@selector(receivedProtoMessage:)]) {
-        dispatch_async(handler.dispatchQueue, ^{
-          [handler receivedProtoMessage:parsed];
-        });
-      }
-    } else {
-      if ([handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
-        dispatch_async(handler.dispatchQueue, ^{
-          [handler closedWithTrailingMetadata:nil error:ErrorForBadProto(message, _responseClass, error)];
-        });
+  dispatch_async(_dispatchQueue, ^{
+    if (self->_handler && message != nil) {
+      NSError *error = nil;
+      GPBMessage *parsed = [self->_responseClass parseFromData:message error:&error];
+      if (parsed) {
+        if ([self->_handler respondsToSelector:@selector(receivedProtoMessage:)]) {
+          [self->_handler receivedProtoMessage:parsed];
+        }
+      } else {
+        if ([self->_handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
+          [self->_handler closedWithTrailingMetadata:nil error:ErrorForBadProto(message, _responseClass, error)];
+        }
+        self->_handler = nil;
+        [self->_call cancel];
+        self->_call = nil;
       }
-      _handler = nil;
-      [_call cancel];
-      _call = nil;
     }
-  }
+  });
 }
 
 - (void)closedWithTrailingMetadata:(NSDictionary *_Nullable)trailingMetadata
                              error:(NSError *_Nullable)error {
-  if (_handler) {
-    id<GRPCProtoResponseHandler> handler = _handler;
-    if ([handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
-      dispatch_async(handler.dispatchQueue, ^{
-        [handler closedWithTrailingMetadata:trailingMetadata error:error];
-      });
+  dispatch_async(_dispatchQueue, ^{
+    if ([self->_handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
+      [self->_handler closedWithTrailingMetadata:trailingMetadata error:error];
     }
-    _handler = nil;
-  }
-  [_call cancel];
-  _call = nil;
+    self->_handler = nil;
+    [self->_call cancel];
+    self->_call = nil;
+  });
 }
 
 - (dispatch_queue_t)dispatchQueue {

src/objective-c/tests/GRPCClientTests.m

@@ -115,22 +115,28 @@ static GRPCProtoMethod *kFullDuplexCallMethod;
 }
 
 - (void)receivedInitialMetadata:(NSDictionary *_Nullable)initialMetadata {
-  if (_initialMetadataCallback) {
-    _initialMetadataCallback(initialMetadata);
-  }
+  dispatch_async(_dispatchQueue, ^{
+    if (_initialMetadataCallback) {
+      _initialMetadataCallback(initialMetadata);
+    }
+  });
 }
 
 - (void)receivedRawMessage:(GPBMessage *_Nullable)message {
-  if (_messageCallback) {
-    _messageCallback(message);
-  }
+  dispatch_async(_dispatchQueue, ^{
+    if (_messageCallback) {
+      _messageCallback(message);
+    }
+  });
 }
 
 - (void)closedWithTrailingMetadata:(NSDictionary *_Nullable)trailingMetadata
                              error:(NSError *_Nullable)error {
-  if (_closeCallback) {
-    _closeCallback(trailingMetadata, error);
-  }
+  dispatch_async(_dispatchQueue, ^{
+    if (_closeCallback) {
+      _closeCallback(trailingMetadata, error);
+    }
+  });
 }
 
 - (dispatch_queue_t)dispatchQueue {

src/objective-c/tests/InteropTests.m

@@ -103,22 +103,28 @@ BOOL isRemoteInteropTest(NSString *host) {
 }
 
 - (void)receivedInitialMetadata:(NSDictionary *_Nullable)initialMetadata {
-  if (_initialMetadataCallback) {
-    _initialMetadataCallback(initialMetadata);
-  }
+  dispatch_async(_dispatchQueue, ^{
+    if (_initialMetadataCallback) {
+      _initialMetadataCallback(initialMetadata);
+    }
+  });
 }
 
 - (void)receivedProtoMessage:(GPBMessage *_Nullable)message {
-  if (_messageCallback) {
-    _messageCallback(message);
-  }
+  dispatch_async(_dispatchQueue, ^{
+    if (_messageCallback) {
+      _messageCallback(message);
+    }
+  });
 }
 
 - (void)closedWithTrailingMetadata:(NSDictionary *_Nullable)trailingMetadata
                              error:(NSError *_Nullable)error {
-  if (_closeCallback) {
-    _closeCallback(trailingMetadata, error);
-  }
+  dispatch_async(_dispatchQueue, ^{
+    if (_closeCallback) {
+      _closeCallback(trailingMetadata, error);
+    }
+  });
 }
 
 - (dispatch_queue_t)dispatchQueue {