Move _channel from GRPCCall into GRPCWrappedCall

src/objective-c/GRPCClient/GRPCCall.m

@@ -37,7 +37,6 @@
 #include <grpc/support/time.h>
 #import <RxLibrary/GRXConcurrentWriteable.h>
 
-#import "private/GRPCChannel.h"
 #import "private/GRPCWrappedCall.h"
 #import "private/NSData+GRPC.h"
 #import "private/NSDictionary+GRPC.h"
@@ -70,8 +69,6 @@ NSString * const kGRPCStatusMetadataKey = @"io.grpc.StatusMetadataKey";
   GRPCWrappedCall *_wrappedCall;
   dispatch_once_t _callAlreadyInvoked;
 
-  GRPCChannel *_channel;
-
   // The C gRPC library has less guarantees on the ordering of events than we
   // do. Particularly, in the face of errors, there's no ordering guarantee at
   // all. This wrapper over our actual writeable ensures thread-safety and
@@ -105,11 +102,7 @@ NSString * const kGRPCStatusMetadataKey = @"io.grpc.StatusMetadataKey";
                 format:@"The requests writer can't be already started."];
   }
   if ((self = [super init])) {
-    _channel = [GRPCChannel channelToHost:host];
-
-    _wrappedCall = [[GRPCWrappedCall alloc] initWithChannel:_channel
-                                                       path:path
-                                                       host:host];
+    _wrappedCall = [[GRPCWrappedCall alloc] initWithHost:host path:path];
 
     // Serial queue to invoke the non-reentrant methods of the grpc_call object.
     _callQueue = dispatch_queue_create("org.grpc.call", NULL);

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

@@ -81,11 +81,12 @@
 
 @end
 
+#pragma mark GRPCWrappedCall
+
 @interface GRPCWrappedCall : NSObject
 
-- (instancetype)initWithChannel:(GRPCChannel *)channel
-                           path:(NSString *)path
-                           host:(NSString *)host NS_DESIGNATED_INITIALIZER;
+- (instancetype)initWithHost:(NSString *)host
+                        path:(NSString *)path NS_DESIGNATED_INITIALIZER;
 
 - (void)startBatchWithOperations:(NSArray *)ops errorHandler:(void(^)())errorHandler;
 

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

@@ -32,10 +32,13 @@
  */
 
 #import "GRPCWrappedCall.h"
+
 #import <Foundation/Foundation.h>
 #include <grpc/grpc.h>
 #include <grpc/byte_buffer.h>
 #include <grpc/support/alloc.h>
+
+#import "GRPCChannel.h"
 #import "GRPCCompletionQueue.h"
 #import "NSDictionary+GRPC.h"
 #import "NSData+GRPC.h"
@@ -219,21 +222,23 @@
 
 @end
 
+#pragma mark GRPCWrappedCall
+
 @implementation GRPCWrappedCall{
+  GRPCChannel *_channel;
   grpc_call *_call;
   GRPCCompletionQueue *_queue;
 }
 
 - (instancetype)init {
-  return [self initWithChannel:nil path:nil host:nil];
+  return [self initWithHost:nil path:nil];
 }
 
-- (instancetype)initWithChannel:(GRPCChannel *)channel
-                           path:(NSString *)path
-                           host:(NSString *)host {
-  if (!channel || !path || !host) {
+- (instancetype)initWithHost:(NSString *)host
+                        path:(NSString *)path {
+  if (!path || !host) {
     [NSException raise:NSInvalidArgumentException
-                format:@"channel, method, and host cannot be nil."];
+                format:@"path and host cannot be nil."];
   }
   
   if (self = [super init]) {
@@ -246,7 +251,11 @@
     if (!_queue) {
       return nil;
     }
-    _call = grpc_channel_create_call(channel.unmanagedChannel,
+    _channel = [GRPCChannel channelToHost:host];
+    if (!_channel) {
+      return nil;
+    }
+    _call = grpc_channel_create_call(_channel.unmanagedChannel,
                                      _queue.unmanagedQueue,
                                      path.UTF8String,
                                      host.UTF8String,