Better use of strong/weak ref to self in GRPCCall

1 files changed, 50 insertions, 37 deletions

diff --git a/src/objective-c/GRPCClient/GRPCCall.m b/src/objective-c/GRPCClient/GRPCCall.m
index ac4596da25..e2c249cead 100644
--- a/src/objective-c/GRPCClient/GRPCCall.m
+++ b/src/objective-c/GRPCClient/GRPCCall.m
@@ -250,11 +250,13 @@ static NSString * const kBearerPrefix = @"Bearer ";
   if (self.state == GRXWriterStatePaused) {
     return;
   }
-  __weak GRPCCall *weakSelf = self;
-  __weak GRXConcurrentWriteable *weakWriteable = _responseWriteable;
 
   dispatch_async(_callQueue, ^{
-    [weakSelf startReadWithHandler:^(grpc_byte_buffer *message) {
+    __weak GRPCCall *weakSelf = self;
+    __weak GRXConcurrentWriteable *weakWriteable = self->_responseWriteable;
+    [self startReadWithHandler:^(grpc_byte_buffer *message) {
+      __strong GRPCCall *strongSelf = weakSelf;
+      __strong GRXConcurrentWriteable *strongWriteable = weakWriteable;
       if (message == NULL) {
         // No more messages from the server
         return;
@@ -266,14 +268,14 @@ static NSString * const kBearerPrefix = @"Bearer ";
         // don't want to throw, because the app shouldn't crash for a behavior
         // that's on the hands of any server to have. Instead we finish and ask
         // the server to cancel.
-        [weakSelf finishWithError:[NSError errorWithDomain:kGRPCErrorDomain
-                                                      code:GRPCErrorCodeResourceExhausted
-                                                  userInfo:@{NSLocalizedDescriptionKey: @"Client does not have enough memory to hold the server response."}]];
-        [weakSelf cancelCall];
+        [strongSelf finishWithError:[NSError errorWithDomain:kGRPCErrorDomain
+                                                        code:GRPCErrorCodeResourceExhausted
+                                                    userInfo:@{NSLocalizedDescriptionKey: @"Client does not have enough memory to hold the server response."}]];
+        [strongSelf cancelCall];
         return;
       }
-      [weakWriteable enqueueValue:data completionHandler:^{
-        [weakSelf startNextRead];
+      [strongWriteable enqueueValue:data completionHandler:^{
+        [strongSelf startNextRead];
       }];
     }];
   });
@@ -333,12 +335,15 @@ static NSString * const kBearerPrefix = @"Bearer ";
     _requestWriter.state = GRXWriterStatePaused;
   }
 
-  __weak GRPCCall *weakSelf = self;
   dispatch_async(_callQueue, ^{
-    [weakSelf writeMessage:value withErrorHandler:^{
-      [weakSelf finishWithError:[NSError errorWithDomain:kGRPCErrorDomain
-                                                    code:GRPCErrorCodeInternal
-                                                userInfo:nil]];
+    __weak GRPCCall *weakSelf = self;
+    [self writeMessage:value withErrorHandler:^{
+      __strong GRPCCall *strongSelf = weakSelf;
+      if (strongSelf != nil) {
+        [strongSelf finishWithError:[NSError errorWithDomain:kGRPCErrorDomain
+                                                        code:GRPCErrorCodeInternal
+                                                    userInfo:nil]];
+      }
     }];
   });
 }
@@ -360,12 +365,13 @@ static NSString * const kBearerPrefix = @"Bearer ";
   if (errorOrNil) {
     [self cancel];
   } else {
-    __weak GRPCCall *weakSelf = self;
     dispatch_async(_callQueue, ^{
-      [weakSelf finishRequestWithErrorHandler:^{
-        [weakSelf finishWithError:[NSError errorWithDomain:kGRPCErrorDomain
-                                                      code:GRPCErrorCodeInternal
-                                                  userInfo:nil]];
+      __weak GRPCCall *weakSelf = self;
+      [self finishRequestWithErrorHandler:^{
+        __strong GRPCCall *strongSelf = weakSelf;
+        [strongSelf finishWithError:[NSError errorWithDomain:kGRPCErrorDomain
+                                                        code:GRPCErrorCodeInternal
+                                                    userInfo:nil]];
       }];
     });
   }
@@ -387,30 +393,37 @@ static NSString * const kBearerPrefix = @"Bearer ";
 }
 
 - (void)invokeCall {
+  __weak GRPCCall *weakSelf = self;
   [self invokeCallWithHeadersHandler:^(NSDictionary *headers) {
     // Response headers received.
-    self.responseHeaders = headers;
-    [self startNextRead];
+    __strong GRPCCall *strongSelf = weakSelf;
+    if (strongSelf) {
+      strongSelf.responseHeaders = headers;
+      [strongSelf startNextRead];
+    }
   } completionHandler:^(NSError *error, NSDictionary *trailers) {
-    self.responseTrailers = trailers;
+    __strong GRPCCall *strongSelf = weakSelf;
+    if (strongSelf) {
+      strongSelf.responseTrailers = trailers;
 
-    if (error) {
-      NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
-      if (error.userInfo) {
-        [userInfo addEntriesFromDictionary:error.userInfo];
-      }
-      userInfo[kGRPCTrailersKey] = self.responseTrailers;
-      // TODO(jcanizales): The C gRPC library doesn't guarantee that the headers block will be
-      // called before this one, so an error might end up with trailers but no headers. We
-      // shouldn't call finishWithError until ater both blocks are called. It is also when this is
-      // done that we can provide a merged view of response headers and trailers in a thread-safe
-      // way.
-      if (self.responseHeaders) {
-        userInfo[kGRPCHeadersKey] = self.responseHeaders;
+      if (error) {
+        NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
+        if (error.userInfo) {
+          [userInfo addEntriesFromDictionary:error.userInfo];
+        }
+        userInfo[kGRPCTrailersKey] = strongSelf.responseTrailers;
+        // TODO(jcanizales): The C gRPC library doesn't guarantee that the headers block will be
+        // called before this one, so an error might end up with trailers but no headers. We
+        // shouldn't call finishWithError until ater both blocks are called. It is also when this is
+        // done that we can provide a merged view of response headers and trailers in a thread-safe
+        // way.
+        if (strongSelf.responseHeaders) {
+          userInfo[kGRPCHeadersKey] = strongSelf.responseHeaders;
+        }
+        error = [NSError errorWithDomain:error.domain code:error.code userInfo:userInfo];
       }
-      error = [NSError errorWithDomain:error.domain code:error.code userInfo:userInfo];
+      [strongSelf finishWithError:error];
     }
-    [self finishWithError:error];
   }];
   // Now that the RPC has been initiated, request writes can start.
   @synchronized(_requestWriter) {