From eab498bef453e221abd4602e6ceff16da659b3c1 Mon Sep 17 00:00:00 2001
From: Muxi Yan <mxyan@google.com>
Date: Wed, 10 Oct 2018 16:44:00 -0700
Subject: [PATCH] Handle GRPCCall2:start: twice

---
 src/objective-c/GRPCClient/GRPCCall.h | 2 +-
 src/objective-c/GRPCClient/GRPCCall.m | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/objective-c/GRPCClient/GRPCCall.h b/src/objective-c/GRPCClient/GRPCCall.h
index 8554860aded..5f6afab08cb 100644
--- a/src/objective-c/GRPCClient/GRPCCall.h
+++ b/src/objective-c/GRPCClient/GRPCCall.h
@@ -235,7 +235,7 @@ extern id const kGRPCTrailersKey;
                        responseHandler:(id<GRPCResponseHandler>)responseHandler;
 
 /**
- * Starts the call. Can only be called once.
+ * Starts the call. This function should only be called once; additional calls will be discarded.
  */
 - (void)start;
 
diff --git a/src/objective-c/GRPCClient/GRPCCall.m b/src/objective-c/GRPCClient/GRPCCall.m
index 6eb9e2e4066..9cb4aa34c24 100644
--- a/src/objective-c/GRPCClient/GRPCCall.m
+++ b/src/objective-c/GRPCClient/GRPCCall.m
@@ -92,6 +92,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
   BOOL _initialMetadataPublished;
   GRXBufferedPipe *_pipe;
   dispatch_queue_t _dispatchQueue;
+  bool _started;
 }
 
 - (instancetype)initWithRequestOptions:(GRPCRequestOptions *)requestOptions
@@ -108,6 +109,7 @@ const char *kCFStreamVarName = "grpc_cfstream";
     _initialMetadataPublished = NO;
     _pipe = [GRXBufferedPipe pipe];
     _dispatchQueue = dispatch_queue_create(NULL, DISPATCH_QUEUE_SERIAL);
+    _started = NO;
   }
 
   return self;
@@ -120,6 +122,10 @@ const char *kCFStreamVarName = "grpc_cfstream";
 
 - (void)start {
   dispatch_async(_dispatchQueue, ^{
+    if (self->_started) {
+      return;
+    }
+    self->_started = YES;
     if (!self->_callOptions) {
       self->_callOptions = [[GRPCCallOptions alloc] init];
     }