Encapsulate grpc_call creation inside GRPCChannel

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

@@ -33,19 +33,19 @@
 
 #import <Foundation/Foundation.h>
 
-struct grpc_channel;
+#include <grpc/grpc.h>
 
-// Each separate instance of this class represents at least one TCP
-// connection to the provided host. To create a grpc_call, pass the
-// value of the unmanagedChannel property to grpc_channel_create_call.
-// Release this object when the call is finished.
+// Each separate instance of this class represents at least one TCP connection to the provided host.
+// To create a grpc_call to that host, use |unmanagedCallWithPath|. Release this object when the
+// call is finished.
 @interface GRPCChannel : NSObject
-@property(nonatomic, readonly) struct grpc_channel *unmanagedChannel;
 
 // Convenience constructor to allow for reuse of connections.
 + (instancetype)channelToHost:(NSString *)host;
 
 - (instancetype)initWithHost:(NSString *)host NS_DESIGNATED_INITIALIZER;
+- (instancetype)initWithChannel:(grpc_channel *)unmanagedChannel
+                       hostName:(NSString *)hostName NS_DESIGNATED_INITIALIZER;
 
-- (instancetype)initWithChannel:(struct grpc_channel *)unmanagedChannel NS_DESIGNATED_INITIALIZER;
+- (grpc_call *)unmanagedCallWithPath:(NSString *)path;
 @end

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

@@ -35,10 +35,15 @@
 
 #include <grpc/grpc.h>
 
+#import "GRPCCompletionQueue.h"
 #import "GRPCSecureChannel.h"
 #import "GRPCUnsecuredChannel.h"
 
-@implementation GRPCChannel
+@implementation GRPCChannel {
+  grpc_channel *_unmanagedChannel;
+  NSString *_hostName;
+  GRPCCompletionQueue *_queue;
+}
 
 + (instancetype)channelToHost:(NSString *)host {
   // TODO(mlumish): Investigate whether a cache with strong links is a good idea
@@ -81,13 +86,32 @@
   return nil; // silence warning.
 }
 
-- (instancetype)initWithChannel:(struct grpc_channel *)unmanagedChannel {
+- (instancetype)initWithChannel:(struct grpc_channel *)unmanagedChannel
+                       hostName:(NSString *)hostName {
+  if (!unmanagedChannel || !hostName) {
+    [NSException raise:NSInvalidArgumentException
+                format:@"Neither unmanagedChannel nor hostName can be nil."];
+  }
   if ((self = [super init])) {
     _unmanagedChannel = unmanagedChannel;
+    _hostName = hostName;
+    // In case sharing the queue creates contention, we can change it to one per grpc_call.
+    _queue = [GRPCCompletionQueue completionQueue];
+    if (!_queue) {
+      return nil;
+    }
   }
   return self;
 }
 
+- (grpc_call *)unmanagedCallWithPath:(NSString *)path {
+  return grpc_channel_create_call(_unmanagedChannel,
+                                  _queue.unmanagedQueue,
+                                  path.UTF8String,
+                                  _hostName.UTF8String,
+                                  gpr_inf_future(GPR_CLOCK_REALTIME));
+}
+
 - (void)dealloc {
   // _unmanagedChannel is NULL when deallocating an object of the base class (because the
   // initializer returns a different object).

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

@@ -54,7 +54,8 @@
   });
   return (self = [super initWithChannel:grpc_secure_channel_create(kCredentials,
                                                                    host.UTF8String,
-                                                                   NULL)]);
+                                                                   NULL)
+                               hostName:host]);
 }
 
 @end

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

@@ -38,7 +38,8 @@
 @implementation GRPCUnsecuredChannel
 
 - (instancetype)initWithHost:(NSString *)host {
-  return (self = [super initWithChannel:grpc_insecure_channel_create(host.UTF8String, NULL)]);
+  return (self = [super initWithChannel:grpc_insecure_channel_create(host.UTF8String, NULL)
+                               hostName:host]);
 }
 
 @end

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

@@ -39,7 +39,6 @@
 #include <grpc/support/alloc.h>
 
 #import "GRPCChannel.h"
-#import "GRPCCompletionQueue.h"
 #import "NSDictionary+GRPC.h"
 #import "NSData+GRPC.h"
 #import "NSError+GRPC.h"
@@ -227,7 +226,6 @@
 @implementation GRPCWrappedCall{
   GRPCChannel *_channel;
   grpc_call *_call;
-  GRPCCompletionQueue *_queue;
 }
 
 - (instancetype)init {
@@ -247,19 +245,8 @@
       grpc_init();
     });
 
-    _queue = [GRPCCompletionQueue completionQueue];
-    if (!_queue) {
-      return nil;
-    }
     _channel = [GRPCChannel channelToHost:host];
-    if (!_channel) {
-      return nil;
-    }
-    _call = grpc_channel_create_call(_channel.unmanagedChannel,
-                                     _queue.unmanagedQueue,
-                                     path.UTF8String,
-                                     host.UTF8String,
-                                     gpr_inf_future(GPR_CLOCK_REALTIME));
+    _call = [_channel unmanagedCallWithPath:path];
     if (_call == NULL) {
       return nil;
     }