Separate GRXForwardingWriter, delete the protocol

src/objective-c/ProtoRPC/ProtoRPC.m

@@ -35,7 +35,7 @@
 
 #import <GPBProtocolBuffers.h>
 #import <RxLibrary/GRXWriteable.h>
-#import <RxLibrary/GRXWriter.h>
+#import <RxLibrary/GRXForwardingWriter.h>
 #import <RxLibrary/GRXWriter+Transformations.h>
 
 @implementation ProtoRPC {
@@ -66,7 +66,7 @@
   }
   // A writer that serializes the proto messages to send.
   id<GRXWriter> bytesWriter =
-      [[[GRXWriter alloc] initWithWriter:requestsWriter] map:^id(GPBMessage *proto) {
+      [[[GRXForwardingWriter alloc] initWithWriter:requestsWriter] map:^id(GPBMessage *proto) {
         // TODO(jcanizales): Fail with an understandable error message if the requestsWriter isn't
         // sending GPBMessages.
         return [proto data];

src/objective-c/RxLibrary/GRXForwardingWriter.h

+/*
+ *
+ * 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 "GRXWriter.h"
+
+// A "proxy" class that simply forwards values, completion, and errors from its
+// input writer to its writeable.
+// It is useful as a superclass for pipes that act as a transformation of their
+// input writer, and for classes that represent objects with input and
+// output sequences of values, like an RPC.
+@interface GRXForwardingWriter : GRXWriter
+- (instancetype)initWithWriter:(id<GRXWriter>)writer NS_DESIGNATED_INITIALIZER;
+@end

src/objective-c/RxLibrary/GRXForwardingWriter.m

+/*
+ *
+ * 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 "GRXForwardingWriter.h"
+
+@interface GRXForwardingWriter () <GRXWriteable>
+@end
+
+@implementation GRXForwardingWriter {
+  id<GRXWriter> _writer;
+  id<GRXWriteable> _writeable;
+}
+
+- (instancetype)init {
+  return [self initWithWriter:nil];
+}
+
+// Designated initializer
+- (instancetype)initWithWriter:(id<GRXWriter>)writer {
+  if (!writer) {
+    [NSException raise:NSInvalidArgumentException format:@"writer can't be nil."];
+  }
+  if ((self = [super init])) {
+    _writer = writer;
+  }
+  return self;
+}
+
+// This is used to send a completion or an error to the writeable. It nillifies
+// our reference to it in order to guarantee no more messages are sent to it,
+// and to release it.
+- (void)finishOutputWithError:(NSError *)errorOrNil {
+  id<GRXWriteable> writeable = _writeable;
+  _writeable = nil;
+  [writeable writesFinishedWithError:errorOrNil];
+}
+
+// This is used to stop the input writer. It nillifies our reference to it
+// to release it.
+- (void)finishInput {
+  id<GRXWriter> writer = _writer;
+  _writer = nil;
+  writer.state = GRXWriterStateFinished;
+}
+
+#pragma mark GRXWriteable implementation
+
+- (void)writeValue:(id)value {
+  [_writeable writeValue:value];
+}
+
+- (void)writesFinishedWithError:(NSError *)errorOrNil {
+  _writer = nil;
+  [self finishOutputWithError:errorOrNil];
+}
+
+#pragma mark GRXWriter implementation
+
+- (GRXWriterState)state {
+  return _writer ? _writer.state : GRXWriterStateFinished;
+}
+
+- (void)setState:(GRXWriterState)state {
+  if (state == GRXWriterStateFinished) {
+    _writeable = nil;
+    [self finishInput];
+  } else {
+    _writer.state = state;
+  }
+}
+
+- (void)startWithWriteable:(id<GRXWriteable>)writeable {
+  _writeable = writeable;
+  [_writer startWithWriteable:self];
+}
+
+- (void)finishWithError:(NSError *)errorOrNil {
+  [self finishOutputWithError:errorOrNil];
+  [self finishInput];
+}
+
+@end

src/objective-c/RxLibrary/GRXWriter.h

@@ -85,7 +85,7 @@ typedef NS_ENUM(NSInteger, GRXWriterState) {
 // Unless otherwise indicated by a conforming class, no messages should be sent
 // concurrently to a GRXWriter. I.e., conforming classes aren't required to
 // be thread-safe.
-@protocol GRXWriter <NSObject>
+@interface GRXWriter : NSObject
 
 // This property can be used to query the current state of the writer, which
 // determines how it might currently use its writeable. Some state transitions can
@@ -116,12 +116,3 @@ typedef NS_ENUM(NSInteger, GRXWriterState) {
 // can't remember the details in the presence of concurrency.
 - (void)finishWithError:(NSError *)errorOrNil;
 @end
-
-// A "proxy" class that simply forwards values, completion, and errors from its
-// input writer to its writeable.
-// It is useful as a superclass for pipes that act as a transformation of their
-// input writer, and for classes that represent objects with input and
-// output sequences of values, like an RPC.
-@interface GRXWriter : NSObject<GRXWriter>
-- (instancetype)initWithWriter:(id<GRXWriter>)writer NS_DESIGNATED_INITIALIZER;
-@end

src/objective-c/RxLibrary/GRXWriter.m

@@ -33,80 +33,6 @@
 
 #import "GRXWriter.h"
 
-@interface GRXWriter () <GRXWriteable>
-@end
-
-@implementation GRXWriter {
-  id<GRXWriter> _writer;
-  id<GRXWriteable> _writeable;
-}
-
-- (instancetype)init {
-  return [self initWithWriter:nil];
-}
-
-// Designated initializer
-- (instancetype)initWithWriter:(id<GRXWriter>)writer {
-  if (!writer) {
-    [NSException raise:NSInvalidArgumentException format:@"writer can't be nil."];
-  }
-  if ((self = [super init])) {
-    _writer = writer;
-  }
-  return self;
-}
-
-// This is used to send a completion or an error to the writeable. It nillifies
-// our reference to it in order to guarantee no more messages are sent to it,
-// and to release it.
-- (void)finishOutputWithError:(NSError *)errorOrNil {
-  id<GRXWriteable> writeable = _writeable;
-  _writeable = nil;
-  [writeable writesFinishedWithError:errorOrNil];
-}
-
-// This is used to stop the input writer. It nillifies our reference to it
-// to release it.
-- (void)finishInput {
-  id<GRXWriter> writer = _writer;
-  _writer = nil;
-  writer.state = GRXWriterStateFinished;
-}
-
-#pragma mark GRXWriteable implementation
-
-- (void)writeValue:(id)value {
-  [_writeable writeValue:value];
-}
-
-- (void)writesFinishedWithError:(NSError *)errorOrNil {
-  _writer = nil;
-  [self finishOutputWithError:errorOrNil];
-}
-
-#pragma mark GRXWriter implementation
-
-- (GRXWriterState)state {
-  return _writer ? _writer.state : GRXWriterStateFinished;
-}
-
-- (void)setState:(GRXWriterState)state {
-  if (state == GRXWriterStateFinished) {
-    _writeable = nil;
-    [self finishInput];
-  } else {
-    _writer.state = state;
-  }
-}
-
-- (void)startWithWriteable:(id<GRXWriteable>)writeable {
-  _writeable = writeable;
-  [_writer startWithWriteable:self];
-}
-
-- (void)finishWithError:(NSError *)errorOrNil {
-  [self finishOutputWithError:errorOrNil];
-  [self finishInput];
-}
+@implementation GRXWriter
 
 @end

src/objective-c/RxLibrary/transformations/GRXMappingWriter.h

@@ -31,10 +31,10 @@
  *
  */
 
-#import "RxLibrary/GRXWriter.h"
+#import "RxLibrary/GRXForwardingWriter.h"
 
 // A "proxy" writer that transforms all the values of its input writer by using a mapping function.
-@interface GRXMappingWriter : GRXWriter
+@interface GRXMappingWriter : GRXForwardingWriter
 - (instancetype)initWithWriter:(id<GRXWriter>)writer map:(id (^)(id value))map
     NS_DESIGNATED_INITIALIZER;
 @end

src/objective-c/RxLibrary/transformations/GRXMappingWriter.m

@@ -37,7 +37,7 @@ static id (^kIdentity)(id value) = ^id(id value) {
   return value;
 };
 
-@interface GRXWriter () <GRXWriteable>
+@interface GRXForwardingWriter () <GRXWriteable>
 @end
 
 @implementation GRXMappingWriter {