Addressed the comments

src/objective-c/GRPCClient/GRPCCall.m

@@ -107,8 +107,11 @@ static NSMutableDictionary *callFlags;
 
   GRPCRequestHeaders *_requestHeaders;
 
+  // In the case that the call is a unary call (i.e. the writer to GRPCCall is of type
+  // GRXImmediateSingleWriter), GRPCCall will delay sending ops (not send them to C core
+  // immediately) and buffer them into a batch _unaryOpBatch. The batch is sent to C core when
+  // the SendClose op is added.
   BOOL _unaryCall;
-
   NSMutableArray *_unaryOpBatch;
 }
 

src/objective-c/GRPCClient/private/GRPCOpBatchLog.h

@@ -31,6 +31,9 @@
  *
  */
 
+
+#ifdef GRPC_TEST_OBJC
+
 /**
  * Logs the op batches of a client. Used for testing.
  */
@@ -52,3 +55,5 @@
 + (NSArray *)obtainAndCleanOpBatchLog;
 
 @end
+
+#endif

src/objective-c/GRPCClient/private/GRPCOpBatchLog.m

@@ -31,11 +31,13 @@
  *
  */
 
+#ifdef GRPC_TEST_OBJC
+
 #import "GRPCOpBatchLog.h"
 
-@implementation GRPCOpBatchLog
+static NSMutableArray *opBatchLog = nil;
 
-NSMutableArray *opBatchLog = nil;
+@implementation GRPCOpBatchLog
 
 + (void)enableOpBatchLog:(BOOL)enabled {
   @synchronized (opBatchLog) {
@@ -65,4 +67,6 @@ NSMutableArray *opBatchLog = nil;
   }
 }
 
-@end
+@end
+
+#endif

src/objective-c/RxLibrary/GRXImmediateSingleWriter.m

@@ -35,41 +35,40 @@
 
 @implementation GRXImmediateSingleWriter {
   id _value;
-  NSError *_errorOrNil;
   id<GRXWriteable> _writeable;
 }
 
 @synthesize state = _state;
 
-- (instancetype)initWithValue:(id)value error:(NSError *)errorOrNil {
+- (instancetype)initWithValue:(id)value {
   if (self = [super init]) {
     _value = value;
-    _errorOrNil = errorOrNil;
     _state = GRXWriterStateNotStarted;
   }
   return self;
 }
 
 + (GRXWriter *)writerWithValue:(id)value {
-  return [[self alloc] initWithValue:value error:nil];
+  return [[self alloc] initWithValue:value];
 }
 
 - (void)startWithWriteable:(id<GRXWriteable>)writeable {
   _state = GRXWriterStateStarted;
   _writeable = writeable;
   [writeable writeValue:_value];
-  [self finishWithError:_errorOrNil];
+  [self finish];
 }
 
-- (void)finishWithError:(NSError *)errorOrNil {
+- (void)finish {
   _state = GRXWriterStateFinished;
-  _errorOrNil = nil;
   _value = nil;
   id<GRXWriteable> writeable = _writeable;
   _writeable = nil;
-  [writeable writesFinishedWithError:errorOrNil];
+  [writeable writesFinishedWithError:nil];
 }
 
+// Overwrite the setter to disallow manual state transition. The getter
+// of _state is synthesized.
 - (void)setState:(GRXWriterState)newState {
   // Manual state transition is not allowed
   return;