Remove -[asDictionary]

src/objective-c/GRPCClient/GRPCCall.m

@@ -236,9 +236,8 @@ NSString * const kGRPCTrailersKey = @"io.grpc.TrailersKey";
 
 - (void)sendHeaders:(GRPCRequestHeaders *)headers {
   // TODO(jcanizales): Add error handlers for async failures
-  [_wrappedCall startBatchWithOperations:@[[[GRPCOpSendMetadata alloc]
-                                            initWithMetadata:[headers asDictionary] ?: @{}
-                                            handler:nil]]];
+  [_wrappedCall startBatchWithOperations:@[[[GRPCOpSendMetadata alloc] initWithMetadata:headers
+                                                                                handler:nil]]];
 }
 
 #pragma mark GRXWriteable implementation

src/objective-c/GRPCClient/GRPCRequestHeaders.h

@@ -38,6 +38,9 @@
 
 @interface GRPCRequestHeaders : NSObject
 
+@property(nonatomic, readonly) NSUInteger count;
+@property(nonatomic, readonly) grpc_metadata *grpc_metadataArray;
+
 - (instancetype)initWithCall:(GRPCCall *)call;
 
 - (id)objectForKeyedSubscript:(NSString *)key;
@@ -46,6 +49,4 @@
 - (void)removeAllObjects;
 - (void)removeObjectForKey:(NSString *)aKey;
 
-- (NSDictionary *)asDictionary;
-
 @end

src/objective-c/GRPCClient/GRPCRequestHeaders.m

@@ -34,6 +34,7 @@
 #import <Foundation/Foundation.h>
 #import "GRPCRequestHeaders.h"
 #import "GRPCCall.h"
+#import "NSDictionary+GRPC.h"
 
 static NSString* normalizeKey(NSString* key) {
   if ([key canBeConvertedToEncoding:NSASCIIStringEncoding]) {
@@ -121,8 +122,13 @@ static bool isKeyValuePairValid(NSString *key, id value) {
   }
 }
 
-- (NSDictionary *)asDictionary {
-  return [NSDictionary dictionaryWithDictionary:_proxy];
+// TODO(jcanizales): Just forward all invocations?
+
+- (NSUInteger)count {
+  return _proxy.count;
 }
 
+- (grpc_metadata *)grpc_metadataArray {
+  return _proxy.grpc_metadataArray;
+}
 @end

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

@@ -36,6 +36,8 @@
 
 #import "GRPCChannel.h"
 
+@class GRPCRequestHeaders;
+
 @interface GRPCOperation : NSObject
 @property(nonatomic, readonly) grpc_op op;
 // Guaranteed to be called when the operation has finished.
@@ -44,7 +46,7 @@
 
 @interface GRPCOpSendMetadata : GRPCOperation
 
-- (instancetype)initWithMetadata:(NSDictionary *)metadata
+- (instancetype)initWithMetadata:(GRPCRequestHeaders *)metadata
                          handler:(void(^)())handler NS_DESIGNATED_INITIALIZER;
 
 @end

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

@@ -38,6 +38,8 @@
 #include <grpc/byte_buffer.h>
 #include <grpc/support/alloc.h>
 
+#import "GRPCRequestHeaders.h"
+
 #import "GRPCCompletionQueue.h"
 #import "GRPCHost.h"
 #import "NSDictionary+GRPC.h"
@@ -65,7 +67,7 @@
   return [self initWithMetadata:nil handler:nil];
 }
 
-- (instancetype)initWithMetadata:(NSDictionary *)metadata handler:(void (^)())handler {
+- (instancetype)initWithMetadata:(GRPCRequestHeaders *)metadata handler:(void (^)())handler {
   if (self = [super init]) {
     _op.op = GRPC_OP_SEND_INITIAL_METADATA;
     _op.data.send_initial_metadata.count = metadata.count;