Subclass GRXWriter instead of conforming to protocol
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.