Subclass GRXWriter instead of conforming to protocol
diff --git a/src/objective-c/GRPCClient/GRPCCall.h b/src/objective-c/GRPCClient/GRPCCall.h
index 1b89ca5..4a8b7ff 100644
--- a/src/objective-c/GRPCClient/GRPCCall.h
+++ b/src/objective-c/GRPCClient/GRPCCall.h
@@ -52,7 +52,7 @@
extern id const kGRPCStatusMetadataKey;
// Represents a single gRPC remote call.
-@interface GRPCCall : NSObject<GRXWriter>
+@interface GRPCCall : GRXWriter
// These HTTP headers will be passed to the server as part of this call. Each HTTP header is a
// name-value pair with string names and either string or binary values.
diff --git a/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.h b/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.h
index 01d053b..9a30a2f 100644
--- a/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.h
+++ b/src/objective-c/GRPCClient/private/GRPCDelegateWrapper.h
@@ -33,8 +33,9 @@
#import <Foundation/Foundation.h>
+#import <RxLibrary/GRXWriter.h>
+
@protocol GRXWriteable;
-@protocol GRXWriter;
// This is a thread-safe wrapper over a GRXWriteable instance. It lets one
// enqueue calls to a GRXWriteable instance for the main thread, guaranteeing
diff --git a/src/objective-c/RxLibrary/GRXBufferedPipe.h b/src/objective-c/RxLibrary/GRXBufferedPipe.h
index 5e876a7..b6296e1 100644
--- a/src/objective-c/RxLibrary/GRXBufferedPipe.h
+++ b/src/objective-c/RxLibrary/GRXBufferedPipe.h
@@ -51,7 +51,7 @@
// 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>
+@interface GRXBufferedPipe : GRXWriter<GRXWriteable>
// Convenience constructor.
+ (instancetype)pipe;
diff --git a/src/objective-c/RxLibrary/GRXImmediateWriter.h b/src/objective-c/RxLibrary/GRXImmediateWriter.h
index 0ba4ac4..b171f0c 100644
--- a/src/objective-c/RxLibrary/GRXImmediateWriter.h
+++ b/src/objective-c/RxLibrary/GRXImmediateWriter.h
@@ -40,7 +40,7 @@
//
// Unless the writeable callback pauses them or stops them early, these writers will do all their
// interactions with the writeable before the start method returns.
-@interface GRXImmediateWriter : NSObject<GRXWriter>
+@interface GRXImmediateWriter : GRXWriter
// Returns a writer that pulls values from the passed NSEnumerator instance and pushes them to
// its writeable. The NSEnumerator is released when it finishes.