Merge github.com:grpc/grpc into mmm-mmm-mmm-mmm

14 files changed, 371 insertions, 49 deletions

diff --git a/src/objective-c/GRPCClient/GRPCCall.m b/src/objective-c/GRPCClient/GRPCCall.m
index 0f458b40cd..a4a0ddb324 100644
--- a/src/objective-c/GRPCClient/GRPCCall.m
+++ b/src/objective-c/GRPCClient/GRPCCall.m
@@ -231,7 +231,7 @@
                                             handler:resumingHandler]] errorHandler:errorHandler];
 }
 
-- (void)didReceiveValue:(id)value {
+- (void)writeValue:(id)value {
   // TODO(jcanizales): Throw/assert if value isn't NSData.
 
   // Pause the input and only resume it when the C layer notifies us that writes
@@ -255,7 +255,7 @@
                             errorHandler:errorHandler];
 }
 
-- (void)didFinishWithError:(NSError *)errorOrNil {
+- (void)writesFinishedWithError:(NSError *)errorOrNil {
   if (errorOrNil) {
     [self cancel];
   } else {
@@ -306,7 +306,7 @@
 
 - (void)startWithWriteable:(id<GRXWriteable>)writeable {
   // The following produces a retain cycle self:_responseWriteable:self, which is only
-  // broken when didFinishWithError: is sent to the wrapped writeable.
+  // broken when writesFinishedWithError: is sent to the wrapped writeable.
   // Care is taken not to retain self strongly in any of the blocks used in
   // the implementation of GRPCCall, so that the life of the instance is
   // determined by this retain cycle.
diff --git a/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.h b/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.h
index 24c2b96729..1ef245fe37 100644
--- a/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.h
+++ b/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.h
@@ -38,11 +38,11 @@
 
 // This is a thread-safe wrapper over a GRXWriteable instance. It lets one
 // enqueue calls to a GRXWriteable instance for the main thread, guaranteeing
-// that didFinishWithError: is the last message sent to it (no matter what
+// that writesFinishedWithError: is the last message sent to it (no matter what
 // messages are sent to the wrapper, in what order, nor from which thread). It
 // also guarantees that, if cancelWithError: is called from the main thread
 // (e.g. by the app cancelling the writes), no further messages are sent to the
-// writeable except didFinishWithError:.
+// writeable except writesFinishedWithError:.
 //
 // TODO(jcanizales): Let the user specify another queue for the writeable
 // callbacks.
@@ -51,23 +51,22 @@
 
 // The GRXWriteable passed is the wrapped writeable.
 // Both the GRXWriter instance and the GRXWriteable instance are retained until
-// didFinishWithError: is sent to the writeable, and released after that.
+// writesFinishedWithError: is sent to the writeable, and released after that.
 // This is used to create a retain cycle that keeps both objects alive until the
 // writing is explicitly finished.
 - (instancetype)initWithWriteable:(id<GRXWriteable>)writeable writer:(id<GRXWriter>)writer
     NS_DESIGNATED_INITIALIZER;
 
-// Enqueues didReceiveValue: to be sent to the writeable in the main thread.
-// The passed handler is invoked from the main thread after didReceiveValue:
-// returns.
+// Enqueues writeValue: to be sent to the writeable in the main thread.
+// The passed handler is invoked from the main thread after writeValue: returns.
 - (void)enqueueMessage:(NSData *)message completionHandler:(void (^)())handler;
 
-// Enqueues didFinishWithError:nil to be sent to the writeable in the main
+// Enqueues writesFinishedWithError:nil to be sent to the writeable in the main
 // thread. After that message is sent to the writeable, all other methods of
 // this object are effectively noops.
 - (void)enqueueSuccessfulCompletion;
 
-// If the writeable has not yet received a didFinishWithError: message, this
+// If the writeable has not yet received a writesFinishedWithError: message, this
 // will enqueue one to be sent to it in the main thread, and cancel all other
 // pending messages to the writeable enqueued by this object (both past and
 // future).
@@ -75,7 +74,7 @@
 - (void)cancelWithError:(NSError *)error;
 
 // Cancels all pending messages to the writeable enqueued by this object (both
-// past and future). Because the writeable won't receive didFinishWithError:,
+// past and future). Because the writeable won't receive writesFinishedWithError:,
 // this also releases the writeable and the writer.
 - (void)cancelSilently;
 @end
diff --git a/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.m b/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.m
index ac444ef406..7d5ecb56d9 100644
--- a/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.m
+++ b/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.m
@@ -43,7 +43,7 @@
 
 @implementation GRPCDelegateWrapper {
   dispatch_queue_t _writeableQueue;
-  // This ensures that didFinishWithError: is only sent once to the writeable.
+  // This ensures that writesFinishedWithError: is only sent once to the writeable.
   dispatch_once_t _alreadyFinished;
 }
 
@@ -69,7 +69,7 @@
     // the race.
     id<GRXWriteable> writeable = self.writeable;
     if (writeable) {
-      [writeable didReceiveValue:message];
+      [writeable writeValue:message];
       handler();
     }
   });
@@ -80,7 +80,7 @@
     dispatch_once(&_alreadyFinished, ^{
       // Cancellation is now impossible. None of the other three blocks can run
       // concurrently with this one.
-      [self.writeable didFinishWithError:nil];
+      [self.writeable writesFinishedWithError:nil];
       // Break the retain cycle with writer, and skip any possible message to the
       // wrapped writeable enqueued after this one.
       self.writeable = nil;
@@ -100,7 +100,7 @@
     self.writeable = nil;
 
     dispatch_async(_writeableQueue, ^{
-      [writeable didFinishWithError:error];
+      [writeable writesFinishedWithError:error];
       // Break the retain cycle with writer.
       self.writer = nil;
     });
diff --git a/src/objective-c/ProtoRPC/ProtoRPC.m b/src/objective-c/ProtoRPC/ProtoRPC.m
index c5051c0123..96608f2898 100644
--- a/src/objective-c/ProtoRPC/ProtoRPC.m
+++ b/src/objective-c/ProtoRPC/ProtoRPC.m
@@ -71,9 +71,9 @@
   if ((self = [super initWithHost:host method:method requestsWriter:bytesWriter])) {
     // A writeable that parses the proto messages received.
     _responseWriteable = [[GRXWriteable alloc] initWithValueHandler:^(NSData *value) {
-      [responsesWriteable didReceiveValue:[responseClass parseFromData:value]];
+      [responsesWriteable writeValue:[responseClass parseFromData:value]];
     } completionHandler:^(NSError *errorOrNil) {
-      [responsesWriteable didFinishWithError:errorOrNil];
+      [responsesWriteable writesFinishedWithError:errorOrNil];
     }];
   }
   return self;
diff --git a/src/objective-c/README.md b/src/objective-c/README.md
index 05e9f2b4dc..cdba3777dd 100644
--- a/src/objective-c/README.md
+++ b/src/objective-c/README.md
@@ -1,3 +1,47 @@
-gRPC implementation for Objective-C on iOS
+# gRPC for Objective-C
 
-This is a work in progress.
+## How to generate a client library from a Protocol Buffers definition
+
+First install v3 of the Protocol Buffers compiler (_protoc_), by cloning [its Git repository](https://github.com/google/protobuf) and following these [installation instructions](https://github.com/google/protobuf#c-installation---unix) (the ones titled C++; don't miss the note for Mac users).
+
+Then clone this repository and execute the following commands from the root directory where it was cloned.
+
+Compile the gRPC plugins for _protoc_:
+```sh
+make plugins
+```
+
+Create a symbolic link to the compiled plugin binary somewhere in your `$PATH`:
+```sh
+ln -s `pwd`/bins/opt/grpc_objective_c_plugin /usr/local/bin/protoc-gen-objcgrpc
+```
+(Notice that the name of the created link must begin with "protoc-gen-" for _protoc_ to recognize it as a plugin).
+
+If you don't want to create the symbolic link, you can alternatively copy the binary (with the appropriate name). Or you might prefer instead to specify the plugin's path as a flag when invoking _protoc_, in which case no system modification nor renaming is necessary.
+
+Finally, run _protoc_ with the following flags to generate the client library for your `.proto` files:
+
+```sh
+protoc --objc_out=. --objcrpc_out=. *.proto
+```
+
+This will generate a pair of `.pbobjc.h`/`.pbobjc.m` files for each `.proto` file, with the messages and enums defined in them. And a pair of `.pbrpc.h`/`.pbrpc.m` files for each `.proto` file with services defined. The latter contains the code to make remote calls to the specified API.
+
+## How to integrate a generated gRPC library in your project
+
+### If you use Cocoapods
+
+This is the recommended approach.
+
+You need to create a Podspec file for the generated library. This is simply a matter of copying an example like [this one](https://github.com/grpc/grpc/blob/master/src/objective-c/examples/Sample/RemoteTestClient/RemoteTest.podspec) to the directory where the source files were generated. Update the name and other metadata of the Podspec as suitable.
+
+Once your library has a Podspec, refer to it from your Podfile using `:path` as described [here](https://guides.cocoapods.org/using/the-podfile.html#using-the-files-from-a-folder-local-to-the-machine).
+
+### If you don't use Cocoapods
+
+You need to compile the generated `.pbpbjc.*` files (the enums and messages) without ARC support, and the generated `.pbrpc.*` files (the services) with ARC support. The generated code depends on v0.3+ of the Objective-C gRPC runtime library and v3.0+ of the Objective-C Protobuf runtime library.
+
+These libraries need to be integrated into your project as described in their respective Podspec files:
+
+* [Podspec](https://github.com/grpc/grpc/blob/master/gRPC.podspec) for the Objective-C gRPC runtime library. This can be tedious to configure manually.
+* [Podspec](https://github.com/jcanizales/protobuf/blob/add-podspec/Protobuf.podspec) for the Objective-C Protobuf runtime library.
diff --git a/src/objective-c/RxLibrary/GRXBufferedPipe.h b/src/objective-c/RxLibrary/GRXBufferedPipe.h
new file mode 100644
index 0000000000..5e876a73bf
--- /dev/null
+++ b/src/objective-c/RxLibrary/GRXBufferedPipe.h
@@ -0,0 +1,59 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#import <Foundation/Foundation.h>
+
+#import "GRXWriteable.h"
+#import "GRXWriter.h"
+
+// A buffered pipe is a Writeable that also acts as a Writer (to whichever other writeable is passed
+// to -startWithWriteable:).
+// Once it is started, whatever values are written into it (via -writeValue:) will be propagated
+// immediately, unless flow control prevents it.
+// If it is throttled and keeps receiving values, as well as if it receives values before being
+// started, it will buffer them and propagate them in order as soon as its state becomes
+// GRXWriterStateStarted.
+// If it receives an error (via -writesFinishedWithError:), it will drop any buffered values and
+// propagate the error immediately.
+//
+// Beware that a pipe of this type can't prevent receiving more values when it is paused (for
+// example if used to write data to a congested network connection). Because in such situations the
+// pipe will keep buffering all data written to it, your application could run out of memory and
+// crash. If you want to react to flow control signals to prevent that, instead of using this class
+// you can implement an object that conforms to GRXWriter.
+@interface GRXBufferedPipe : NSObject<GRXWriteable, GRXWriter>
+
+// Convenience constructor.
++ (instancetype)pipe;
+
+@end
diff --git a/src/objective-c/RxLibrary/GRXBufferedPipe.m b/src/objective-c/RxLibrary/GRXBufferedPipe.m
new file mode 100644
index 0000000000..4820c84af0
--- /dev/null
+++ b/src/objective-c/RxLibrary/GRXBufferedPipe.m
@@ -0,0 +1,146 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#import "GRXBufferedPipe.h"
+
+@implementation GRXBufferedPipe {
+  id<GRXWriteable> _writeable;
+  NSMutableArray *_queue;
+  BOOL _inputIsFinished;
+  NSError *_errorOrNil;
+}
+
+@synthesize state = _state;
+
++ (instancetype)pipe {
+  return [[self alloc] init];
+}
+
+- (instancetype)init {
+  if (self = [super init]) {
+    _queue = [NSMutableArray array];
+    _state = GRXWriterStateNotStarted;
+  }
+  return self;
+}
+
+- (id)popValue {
+  id value = _queue[0];
+  [_queue removeObjectAtIndex:0];
+  return value;
+}
+
+- (void)writeBufferUntilPausedOrStopped {
+  while (_state == GRXWriterStateStarted && _queue.count > 0) {
+    [_writeable writeValue:[self popValue]];
+  }
+  if (_inputIsFinished && _queue.count == 0) {
+    // Our writer finished normally while we were paused or not-started-yet.
+    [self finishWithError:_errorOrNil];
+  }
+}
+
+#pragma mark GRXWriteable implementation
+
+// Returns whether events can be simply propagated to the other end of the pipe.
+- (BOOL)shouldFastForward {
+  return _state == GRXWriterStateStarted && _queue.count == 0;
+}
+
+- (void)writeValue:(id)value {
+  if (self.shouldFastForward) {
+    // Skip the queue.
+    [_writeable writeValue:value];
+  } else {
+    // Even if we're paused and with enqueued values, we can't excert back-pressure to our writer.
+    // So just buffer the new value.
+    // We need a copy, so that it doesn't mutate before it's written at the other end of the pipe.
+    if ([value respondsToSelector:@selector(copy)]) {
+      value = [value copy];
+    }
+    [_queue addObject:value];
+  }
+}
+
+- (void)writesFinishedWithError:(NSError *)errorOrNil {
+  _inputIsFinished = YES;
+  _errorOrNil = errorOrNil;
+  if (errorOrNil || self.shouldFastForward) {
+    // No need to write pending values.
+    [self finishWithError:_errorOrNil];
+  }
+}
+
+#pragma mark GRXWriter implementation
+
+- (void)setState:(GRXWriterState)newState {
+  // Manual transitions are only allowed from the started or paused states.
+  if (_state == GRXWriterStateNotStarted || _state == GRXWriterStateFinished) {
+    return;
+  }
+
+  switch (newState) {
+    case GRXWriterStateFinished:
+      _state = newState;
+      _queue = nil;
+      // Per GRXWriter's contract, setting the state to Finished manually means one doesn't wish the
+      // writeable to be messaged anymore.
+      _writeable = nil;
+      return;
+    case GRXWriterStatePaused:
+      _state = newState;
+      return;
+    case GRXWriterStateStarted:
+      if (_state == GRXWriterStatePaused) {
+        _state = newState;
+        [self writeBufferUntilPausedOrStopped];
+      }
+      return;
+    case GRXWriterStateNotStarted:
+      return;
+  }
+}
+
+- (void)startWithWriteable:(id<GRXWriteable>)writeable {
+  _state = GRXWriterStateStarted;
+  _writeable = writeable;
+  [self writeBufferUntilPausedOrStopped];
+}
+
+- (void)finishWithError:(NSError *)errorOrNil {
+  id<GRXWriteable> writeable = _writeable;
+  self.state = GRXWriterStateFinished;
+  [writeable writesFinishedWithError:errorOrNil];
+}
+
+@end
diff --git a/src/objective-c/RxLibrary/GRXImmediateWriter.m b/src/objective-c/RxLibrary/GRXImmediateWriter.m
index 7468af557f..0b4979872e 100644
--- a/src/objective-c/RxLibrary/GRXImmediateWriter.m
+++ b/src/objective-c/RxLibrary/GRXImmediateWriter.m
@@ -109,7 +109,7 @@
 - (void)writeUntilPausedOrStopped {
   id value;
   while (value = [_enumerator nextObject]) {
-    [_writeable didReceiveValue:value];
+    [_writeable writeValue:value];
     // If the writeable has a reference to us, it might change our state to paused or finished.
     if (_state == GRXWriterStatePaused || _state == GRXWriterStateFinished) {
       return;
@@ -130,7 +130,7 @@
   _errorOrNil = nil;
   id<GRXWriteable> writeable = _writeable;
   _writeable = nil;
-  [writeable didFinishWithError:errorOrNil];
+  [writeable writesFinishedWithError:errorOrNil];
 }
 
 - (void)setState:(GRXWriterState)newState {
diff --git a/src/objective-c/RxLibrary/GRXWriteable.h b/src/objective-c/RxLibrary/GRXWriteable.h
index 6f6ea142e0..216de30735 100644
--- a/src/objective-c/RxLibrary/GRXWriteable.h
+++ b/src/objective-c/RxLibrary/GRXWriteable.h
@@ -38,14 +38,12 @@
 @protocol GRXWriteable <NSObject>
 
 // Push the next value of the sequence to the receiving object.
-// TODO(jcanizales): Name it enumerator:(id<GRXEnumerator>) didProduceValue:(id)?
-- (void)didReceiveValue:(id)value;
+- (void)writeValue:(id)value;
 
 // Signal that the sequence is completed, or that an error ocurred. After this
-// message is sent to the instance, neither it nor didReceiveValue: may be
+// message is sent to the instance, neither it nor writeValue: may be
 // called again.
-// TODO(jcanizales): enumerator:(id<GRXEnumerator>) didFinishWithError:(NSError*)?
-- (void)didFinishWithError:(NSError *)errorOrNil;
+- (void)writesFinishedWithError:(NSError *)errorOrNil;
 @end
 
 typedef void (^GRXValueHandler)(id value);
diff --git a/src/objective-c/RxLibrary/GRXWriteable.m b/src/objective-c/RxLibrary/GRXWriteable.m
index 7000a078d1..63f7c3e7f3 100644
--- a/src/objective-c/RxLibrary/GRXWriteable.m
+++ b/src/objective-c/RxLibrary/GRXWriteable.m
@@ -76,13 +76,13 @@
   return self;
 }
 
-- (void)didReceiveValue:(id)value {
+- (void)writeValue:(id)value {
   if (_valueHandler) {
     _valueHandler(value);
   }
 }
 
-- (void)didFinishWithError:(NSError *)errorOrNil {
+- (void)writesFinishedWithError:(NSError *)errorOrNil {
   if (_completionHandler) {
     _completionHandler(errorOrNil);
   }
diff --git a/src/objective-c/RxLibrary/GRXWriter.h b/src/objective-c/RxLibrary/GRXWriter.h
index 68c294f007..dcf44e3143 100644
--- a/src/objective-c/RxLibrary/GRXWriter.h
+++ b/src/objective-c/RxLibrary/GRXWriter.h
@@ -50,7 +50,7 @@ typedef NS_ENUM(NSInteger, GRXWriterState) {
   // The writer is temporarily paused, and won't send any more values to the
   // writeable unless its state is set back to Started. The writer might still
   // transition to the Finished state at any moment, and is allowed to send
-  // didFinishWithError: to its writeable.
+  // writesFinishedWithError: to its writeable.
   //
   // Not all implementations of writer have to support pausing, and thus
   // trying to set an writer's state to this value might have no effect.
@@ -59,7 +59,7 @@ typedef NS_ENUM(NSInteger, GRXWriterState) {
   // The writer has released its writeable and won't interact with it anymore.
   //
   // One seldomly wants to set an writer's state to this value, as its
-  // writeable isn't notified with a didFinishWithError: message. Instead, sending
+  // writeable isn't notified with a writesFinishedWithError: message. Instead, sending
   // finishWithError: to the writer will make it notify the writeable and then
   // transition to this state.
   GRXWriterStateFinished
@@ -105,7 +105,7 @@ typedef NS_ENUM(NSInteger, GRXWriterState) {
 // This method might only be called on writers in the NotStarted state.
 - (void)startWithWriteable:(id<GRXWriteable>)writeable;
 
-// Send didFinishWithError:errorOrNil immediately to the writeable, and don't send
+// Send writesFinishedWithError:errorOrNil immediately to the writeable, and don't send
 // any more messages to it.
 //
 // This method might only be called on writers in the Started or Paused
diff --git a/src/objective-c/RxLibrary/GRXWriter.m b/src/objective-c/RxLibrary/GRXWriter.m
index b48a44f3a7..cc14383560 100644
--- a/src/objective-c/RxLibrary/GRXWriter.m
+++ b/src/objective-c/RxLibrary/GRXWriter.m
@@ -62,7 +62,7 @@
 - (void)finishOutputWithError:(NSError *)errorOrNil {
   id<GRXWriteable> writeable = _writeable;
   _writeable = nil;
-  [writeable didFinishWithError:errorOrNil];
+  [writeable writesFinishedWithError:errorOrNil];
 }
 
 // This is used to stop the input writer. It nillifies our reference to it
@@ -75,11 +75,11 @@
 
 #pragma mark GRXWriteable implementation
 
-- (void)didReceiveValue:(id)value {
-  [_writeable didReceiveValue:value];
+- (void)writeValue:(id)value {
+  [_writeable writeValue:value];
 }
 
-- (void)didFinishWithError:(NSError *)errorOrNil {
+- (void)writesFinishedWithError:(NSError *)errorOrNil {
   _writer = nil;
   [self finishOutputWithError:errorOrNil];
 }
diff --git a/src/objective-c/RxLibrary/transformations/GRXMappingWriter.m b/src/objective-c/RxLibrary/transformations/GRXMappingWriter.m
index 8a41c819a6..2cdfea1b67 100644
--- a/src/objective-c/RxLibrary/transformations/GRXMappingWriter.m
+++ b/src/objective-c/RxLibrary/transformations/GRXMappingWriter.m
@@ -57,7 +57,7 @@ static id (^kIdentity)(id value) = ^id(id value) {
 }
 
 // Override
-- (void)didReceiveValue:(id)value {
-  [super didReceiveValue:_map(value)];
+- (void)writeValue:(id)value {
+  [super writeValue:_map(value)];
 }
 @end
diff --git a/src/objective-c/examples/Sample/SampleTests/RemoteProtoTests.m b/src/objective-c/examples/Sample/SampleTests/RemoteProtoTests.m
index f489229834..7e063fddb4 100644
--- a/src/objective-c/examples/Sample/SampleTests/RemoteProtoTests.m
+++ b/src/objective-c/examples/Sample/SampleTests/RemoteProtoTests.m
@@ -36,13 +36,46 @@
 #import <UIKit/UIKit.h>
 #import <XCTest/XCTest.h>
 
-#import <gRPC/ProtoRPC.h>
 #import <gRPC/GRXWriter+Immediate.h>
+#import <gRPC/GRXBufferedPipe.h>
+#import <gRPC/ProtoRPC.h>
 #import <RemoteTest/Empty.pbobjc.h>
 #import <RemoteTest/Messages.pbobjc.h>
 #import <RemoteTest/Test.pbobjc.h>
 #import <RemoteTest/Test.pbrpc.h>
 
+// Convenience constructors for the generated proto messages:
+
+@interface RMTStreamingOutputCallRequest (Constructors)
++ (instancetype)messageWithPayloadSize:(NSNumber *)payloadSize
+                 requestedResponseSize:(NSNumber *)responseSize;
+@end
+
+@implementation RMTStreamingOutputCallRequest (Constructors)
++ (instancetype)messageWithPayloadSize:(NSNumber *)payloadSize
+                 requestedResponseSize:(NSNumber *)responseSize {
+  RMTStreamingOutputCallRequest *request = [self message];
+  RMTResponseParameters *parameters = [RMTResponseParameters message];
+  parameters.size = responseSize.integerValue;
+  [request.responseParametersArray addObject:parameters];
+  request.payload.body = [NSMutableData dataWithLength:payloadSize.unsignedIntegerValue];
+  return request;
+}
+@end
+
+@interface RMTStreamingOutputCallResponse (Constructors)
++ (instancetype)messageWithPayloadSize:(NSNumber *)payloadSize;
+@end
+
+@implementation RMTStreamingOutputCallResponse (Constructors)
++ (instancetype)messageWithPayloadSize:(NSNumber *)payloadSize {
+  RMTStreamingOutputCallResponse * response = [self message];
+  response.payload.type = RMTPayloadType_Compressable;
+  response.payload.body = [NSMutableData dataWithLength:payloadSize.unsignedIntegerValue];
+  return response;
+}
+@end
+
 @interface RemoteProtoTests : XCTestCase
 @end
 
@@ -70,7 +103,7 @@
     [expectation fulfill];
   }];
 
-  [self waitForExpectationsWithTimeout:2. handler:nil];
+  [self waitForExpectationsWithTimeout:2 handler:nil];
 }
 
 - (void)testLargeUnaryRPC {
@@ -92,7 +125,7 @@
     [expectation fulfill];
   }];
 
-  [self waitForExpectationsWithTimeout:4. handler:nil];
+  [self waitForExpectationsWithTimeout:4 handler:nil];
 }
 
 - (void)testClientStreamingRPC {
@@ -124,7 +157,7 @@
     [expectation fulfill];
   }];
 
-  [self waitForExpectationsWithTimeout:4. handler:nil];
+  [self waitForExpectationsWithTimeout:4 handler:nil];
 }
 
 - (void)testServerStreamingRPC {
@@ -149,10 +182,7 @@
 
     if (response) {
       XCTAssertLessThan(index, 4, @"More than 4 responses received.");
-      RMTStreamingOutputCallResponse * expected = [RMTStreamingOutputCallResponse message];
-      expected.payload.type = RMTPayloadType_Compressable;
-      int expectedSize = [expectedSizes[index] unsignedIntegerValue];
-      expected.payload.body = [NSMutableData dataWithLength:expectedSize];
+      id expected = [RMTStreamingOutputCallResponse messageWithPayloadSize:expectedSizes[index]];
       XCTAssertEqualObjects(response, expected);
       index += 1;
     }
@@ -166,6 +196,49 @@
   [self waitForExpectationsWithTimeout:4 handler:nil];
 }
 
+- (void)testPingPongRPC {
+  __weak XCTestExpectation *expectation = [self expectationWithDescription:@"PingPong"];
+
+  NSArray *requests = @[@27182, @8, @1828, @45904];
+  NSArray *responses = @[@31415, @9, @2653, @58979];
+
+  GRXBufferedPipe *requestsBuffer = [[GRXBufferedPipe alloc] init];
+
+  __block int index = 0;
+
+  id request = [RMTStreamingOutputCallRequest messageWithPayloadSize:requests[index]
+                                               requestedResponseSize:responses[index]];
+  [requestsBuffer writeValue:request];
+
+  [_service fullDuplexCallWithRequestsWriter:requestsBuffer
+                                     handler:^(BOOL done,
+                                               RMTStreamingOutputCallResponse *response,
+                                               NSError *error) {
+    XCTAssertNil(error, @"Finished with unexpected error: %@", error);
+    XCTAssertTrue(done || response, @"Event handler called without an event.");
+
+    if (response) {
+      XCTAssertLessThan(index, 4, @"More than 4 responses received.");
+      id expected = [RMTStreamingOutputCallResponse messageWithPayloadSize:responses[index]];
+      XCTAssertEqualObjects(response, expected);
+      index += 1;
+      if (index < 4) {
+        id request = [RMTStreamingOutputCallRequest messageWithPayloadSize:requests[index]
+                                                     requestedResponseSize:responses[index]];
+        [requestsBuffer writeValue:request];
+      } else {
+        [requestsBuffer writesFinishedWithError:nil];
+      }
+    }
+                                       
+    if (done) {
+      XCTAssertEqual(index, 4, @"Received %i responses instead of 4.", index);
+      [expectation fulfill];
+    }
+  }];
+  [self waitForExpectationsWithTimeout:2 handler:nil];
+}
+
 - (void)testEmptyStreamRPC {
   __weak XCTestExpectation *expectation = [self expectationWithDescription:@"EmptyStream"];
   [_service fullDuplexCallWithRequestsWriter:[GRXWriter emptyWriter]
@@ -176,13 +249,16 @@
     XCTAssert(done, @"Unexpected response: %@", response);
     [expectation fulfill];
   }];
-  [self waitForExpectationsWithTimeout:4 handler:nil];
+  [self waitForExpectationsWithTimeout:2 handler:nil];
 }
 
 - (void)testCancelAfterBeginRPC {
   __weak XCTestExpectation *expectation = [self expectationWithDescription:@"CancelAfterBegin"];
-  // TODO(mlumish): change to writing that blocks instead of writing
-  ProtoRPC *call = [_service RPCToStreamingInputCallWithRequestsWriter:[GRXWriter emptyWriter]
+
+  // A buffered pipe to which we never write any value acts as a writer that just hangs.
+  GRXBufferedPipe *requestsBuffer = [[GRXBufferedPipe alloc] init];
+
+  ProtoRPC *call = [_service RPCToStreamingInputCallWithRequestsWriter:requestsBuffer
                                                                handler:^(RMTStreamingInputCallResponse *response,
                                                                          NSError *error) {
     XCTAssertEqual(error.code, GRPC_STATUS_CANCELLED);