Merge pull request #4985 from kriswuollett/kriswuollett-objc-useragent

Add channel args to enable user agent string for Objective-C

8 files changed, 245 insertions, 210 deletions

diff --git a/src/objective-c/GRPCClient/private/GRPCUnsecuredChannel.h b/src/objective-c/GRPCClient/GRPCCall+ChannelArg.h
index 8528be44c0..bd6b064f16 100644
--- a/src/objective-c/GRPCClient/private/GRPCUnsecuredChannel.h
+++ b/src/objective-c/GRPCClient/GRPCCall+ChannelArg.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -30,9 +30,17 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
+#import "GRPCCall.h"
 
-#import "GRPCChannel.h"
+/**
+ * Methods to configure GRPC channel options.
+ */
+@interface GRPCCall (ChannelArg)
+
+/**
+ * Use the provided @c userAgentPrefix at the beginning of the HTTP User Agent string for all calls
+ * to the specified @c host.
+ */
++ (void)setUserAgentPrefix:(NSString *)userAgentPrefix forHost:(NSString *)host;
 
-@interface GRPCUnsecuredChannel : GRPCChannel
-- (instancetype)initWithHost:(NSString *)host NS_DESIGNATED_INITIALIZER;
 @end
diff --git a/src/objective-c/GRPCClient/private/GRPCUnsecuredChannel.m b/src/objective-c/GRPCClient/GRPCCall+ChannelArg.m
index 15b6ffc75c..5f9932d86d 100644
--- a/src/objective-c/GRPCClient/private/GRPCUnsecuredChannel.m
+++ b/src/objective-c/GRPCClient/GRPCCall+ChannelArg.m
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,20 +31,19 @@
  *
  */
 
-#import "GRPCUnsecuredChannel.h"
+#import "GRPCCall+ChannelArg.h"
 
-#include <grpc/grpc.h>
+#import "private/GRPCHost.h"
 
-@implementation GRPCUnsecuredChannel
+@implementation GRPCCall (ChannelArg)
 
-- (instancetype)initWithHost:(NSString *)host {
-  return (self = [super initWithChannel:grpc_insecure_channel_create(host.UTF8String, NULL, NULL)]);
++ (void)setUserAgentPrefix:(NSString *)userAgentPrefix forHost:(NSString *)host {
+  if (!host) {
+    [NSException raise:NSInvalidArgumentException
+                format:@"host and userAgentPrefix must be provided."];
+  }
+  GRPCHost *hostConfig = [GRPCHost hostWithAddress:host];
+  hostConfig.userAgentPrefix = userAgentPrefix;
 }
 
-// TODO(jcanizales): GRPCSecureChannel and GRPCUnsecuredChannel are just convenience initializers
-// for GRPCChannel. Move them into GRPCChannel, which will make the following unnecessary.
-- (instancetype)initWithChannel:(grpc_channel *)unmanagedChannel {
-  [NSException raise:NSInternalInconsistencyException format:@"use the other initializer"];
-  return [self initWithHost:nil]; // silence warnings
-}
 @end
diff --git a/src/objective-c/GRPCClient/private/GRPCChannel.h b/src/objective-c/GRPCClient/private/GRPCChannel.h
index e2d19d506a..1888dea1b4 100644
--- a/src/objective-c/GRPCClient/private/GRPCChannel.h
+++ b/src/objective-c/GRPCClient/private/GRPCChannel.h
@@ -33,18 +33,51 @@
 
 #import <Foundation/Foundation.h>
 
-struct grpc_channel;
+#include <grpc/grpc.h>
+
+struct grpc_channel_credentials;
+
 
 /**
  * Each separate instance of this class represents at least one TCP connection to the provided host.
- * Create them using one of the subclasses |GRPCSecureChannel| and |GRPCUnsecuredChannel|.
  */
 @interface GRPCChannel : NSObject
-@property(nonatomic, readonly) struct grpc_channel *unmanagedChannel;
+
+@property(nonatomic, readonly, nonnull) struct grpc_channel *unmanagedChannel;
+
+- (nullable instancetype)init NS_UNAVAILABLE;
 
 /**
- * This initializer takes ownership of the passed channel, and will destroy it when this object is
- * deallocated. It's illegal to pass the same grpc_channel to two different GRPCChannel objects.
+ * Creates a secure channel to the specified @c host using default credentials and channel
+ * arguments. If certificates could not be found to create a secure channel, then @c nil is
+ * returned.
  */
-- (instancetype)initWithChannel:(struct grpc_channel *)unmanagedChannel NS_DESIGNATED_INITIALIZER;
++ (nullable GRPCChannel *)secureChannelWithHost:(nonnull NSString *)host;
+
+/**
+ * Creates a secure channel to the specified @c host using the specified @c pathToCertificates and 
+ * @c channelArgs. Only in tests should @c pathToCertificates be nil or
+ * @c GRPC_SSL_TARGET_NAME_OVERRIDE_ARG channel arg be set. Passing nil for @c pathToCertificates
+ * results in using the default root certificates distributed with the library. If certificates
+ * could not be found in any case, then @c nil is returned.
+ */
++ (nullable GRPCChannel *)secureChannelWithHost:(nonnull NSString *)host
+                             pathToCertificates:(nullable NSString *)pathToCertificates
+                                    channelArgs:(nullable NSDictionary *)channelArgs;
+
+
+/**
+ * Creates a secure channel to the specified @c host using the specified @c credentials and
+ * @c channelArgs. Only in tests should @c GRPC_SSL_TARGET_NAME_OVERRIDE_ARG channel arg be set.
+ */
++ (nonnull GRPCChannel *)secureChannelWithHost:(nonnull NSString *)host
+    credentials:(nonnull struct grpc_channel_credentials *)credentials
+    channelArgs:(nullable NSDictionary *)channelArgs;
+
+/**
+ * Creates an insecure channel to the specified @c host using the specified @c channelArgs.
+ */
++ (nonnull GRPCChannel *)insecureChannelWithHost:(nonnull NSString *)host
+                                     channelArgs:(nullable NSDictionary *)channelArgs;
+
 @end
diff --git a/src/objective-c/GRPCClient/private/GRPCChannel.m b/src/objective-c/GRPCClient/private/GRPCChannel.m
index 4366e63320..7a676060c1 100644
--- a/src/objective-c/GRPCClient/private/GRPCChannel.m
+++ b/src/objective-c/GRPCClient/private/GRPCChannel.m
@@ -33,22 +33,114 @@
 
 #import "GRPCChannel.h"
 
-#include <grpc/grpc.h>
+#include <grpc/grpc_security.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
 
-@implementation GRPCChannel
+/**
+ * Returns @c grpc_channel_credentials from the specified @c path. If the file at the path could not
+ * be read then NULL is returned. If NULL is returned, @c errorPtr may not be NULL if there are
+ * details available describing what went wrong.
+ */
+static grpc_channel_credentials *CertificatesAtPath(NSString *path, NSError **errorPtr) {
+  // Files in PEM format can have non-ASCII characters in their comments (e.g. for the name of the
+  // issuer). Load them as UTF8 and produce an ASCII equivalent.
+  NSString *contentInUTF8 = [NSString stringWithContentsOfFile:path
+                                                      encoding:NSUTF8StringEncoding
+                                                         error:errorPtr];
+  NSData *contentInASCII = [contentInUTF8 dataUsingEncoding:NSASCIIStringEncoding
+                                       allowLossyConversion:YES];
+  if (!contentInASCII.bytes) {
+    // Passing NULL to grpc_ssl_credentials_create produces behavior we don't want, so return.
+    return NULL;
+  }
+  return grpc_ssl_credentials_create(contentInASCII.bytes, NULL, NULL);
+}
+
+void freeChannelArgs(grpc_channel_args *channel_args) {
+  for (size_t i = 0; i < channel_args->num_args; ++i) {
+    grpc_arg *arg = &channel_args->args[i];
+    gpr_free(arg->key);
+    if (arg->type == GRPC_ARG_STRING) {
+      gpr_free(arg->value.string);
+    }
+  }
+  gpr_free(channel_args);
+}
+
+/**
+ * Allocates a @c grpc_channel_args and populates it with the options specified in the
+ * @c dictionary. Keys must be @c NSString. If the value responds to @c @selector(UTF8String) then
+ * it will be mapped to @c GRPC_ARG_STRING. If not, it will be mapped to @c GRPC_ARG_INTEGER if the
+ * value responds to @c @selector(intValue). Otherwise, an exception will be raised. The caller of
+ * this function is responsible for calling @c freeChannelArgs on a non-NULL returned value.
+ */
+grpc_channel_args * buildChannelArgs(NSDictionary *dictionary) {
+  if (!dictionary) {
+    return NULL;
+  }
 
-- (instancetype)init {
-  return [self initWithChannel:NULL];
+  NSArray *keys = [dictionary allKeys];
+  NSUInteger argCount = [keys count];
+
+  grpc_channel_args *channelArgs = gpr_malloc(sizeof(grpc_channel_args));
+  channelArgs->num_args = argCount;
+  channelArgs->args = gpr_malloc(argCount * sizeof(grpc_arg));
+
+  // TODO(kriswuollett) Check that keys adhere to GRPC core library requirements
+
+  for (NSUInteger i = 0; i < argCount; ++i) {
+    grpc_arg *arg = &channelArgs->args[i];
+    arg->key = gpr_strdup([keys[i] UTF8String]);
+
+    id value = dictionary[keys[i]];
+    if ([value respondsToSelector:@selector(UTF8String)]) {
+      arg->type = GRPC_ARG_STRING;
+      arg->value.string = gpr_strdup([value UTF8String]);
+    } else if ([value respondsToSelector:@selector(intValue)]) {
+      arg->type = GRPC_ARG_INTEGER;
+      arg->value.integer = [value intValue];
+    } else {
+      [NSException raise:NSInvalidArgumentException
+                  format:@"Invalid value type: %@", [value class]];
+    }
+  }
+
+  return channelArgs;
+}
+
+@implementation GRPCChannel {
+  // Retain arguments to channel_create because they may not be used on the thread that invoked
+  // the channel_create function.
+  NSString *_host;
+  grpc_channel_args *_channelArgs;
 }
 
-// Designated initializer
-- (instancetype)initWithChannel:(grpc_channel *)unmanagedChannel {
-  if (!unmanagedChannel) {
+
+- (instancetype)initWithHost:(NSString *)host
+                      secure:(BOOL)secure
+                 credentials:(struct grpc_channel_credentials *)credentials
+                 channelArgs:(NSDictionary *)channelArgs {
+  if (!host) {
+    [NSException raise:NSInvalidArgumentException format:@"host argument missing"];
+  }
+
+  if (secure && !credentials) {
     return nil;
   }
-  if ((self = [super init])) {
-    _unmanagedChannel = unmanagedChannel;
+
+  if (self = [super init]) {
+    _channelArgs = buildChannelArgs(channelArgs);
+    _host = [host copy];
+    if (secure) {
+      _unmanagedChannel = grpc_secure_channel_create(credentials, _host.UTF8String, _channelArgs,
+                                                     NULL);
+    } else {
+      _unmanagedChannel = grpc_insecure_channel_create(_host.UTF8String, _channelArgs, NULL);
+    }
   }
+
   return self;
 }
 
@@ -56,5 +148,61 @@
   // TODO(jcanizales): Be sure to add a test with a server that closes the connection prematurely,
   // as in the past that made this call to crash.
   grpc_channel_destroy(_unmanagedChannel);
+  freeChannelArgs(_channelArgs);
 }
+
++ (GRPCChannel *)secureChannelWithHost:(NSString *)host {
+  return [[GRPCChannel alloc] initWithHost:host secure:YES credentials:NULL channelArgs:NULL];
+}
+
++ (GRPCChannel *)secureChannelWithHost:(NSString *)host
+                    pathToCertificates:(NSString *)path
+                           channelArgs:(NSDictionary *)channelArgs {
+  // Load default SSL certificates once.
+  static grpc_channel_credentials *kDefaultCertificates;
+  static dispatch_once_t loading;
+  dispatch_once(&loading, ^{
+    NSString *defaultPath = @"gRPCCertificates.bundle/roots"; // .pem
+    // Do not use NSBundle.mainBundle, as it's nil for tests of library projects.
+    NSBundle *bundle = [NSBundle bundleForClass:self.class];
+    NSString *path = [bundle pathForResource:defaultPath ofType:@"pem"];
+    NSError *error;
+    kDefaultCertificates = CertificatesAtPath(path, &error);
+    NSAssert(kDefaultCertificates, @"Could not read %@/%@.pem. This file, with the root "
+             "certificates, is needed to establish secure (TLS) connections. Because the file is "
+             "distributed with the gRPC library, this error is usually a sign that the library "
+             "wasn't configured correctly for your project. Error: %@",
+             bundle.bundlePath, defaultPath, error);
+  });
+
+  //TODO(jcanizales): Add NSError** parameter to the initializer.
+  grpc_channel_credentials *certificates = path
+      ? CertificatesAtPath(path, NULL)
+      : kDefaultCertificates;
+
+  return [[GRPCChannel alloc] initWithHost:host
+                                    secure:YES
+                               credentials:certificates
+                               channelArgs:channelArgs];
+}
+
+
++ (GRPCChannel *)secureChannelWithHost:(NSString *)host
+                           credentials:(struct grpc_channel_credentials *)credentials
+                           channelArgs:(NSDictionary *)channelArgs {
+  return [[GRPCChannel alloc] initWithHost:host
+                                    secure:YES
+                               credentials:credentials
+                               channelArgs:channelArgs];
+
+}
+
++ (GRPCChannel *)insecureChannelWithHost:(NSString *)host
+                             channelArgs:(NSDictionary *)channelArgs {
+  return [[GRPCChannel alloc] initWithHost:host
+                                    secure:NO
+                               credentials:NULL
+                               channelArgs:channelArgs];
+}
+
 @end
diff --git a/src/objective-c/GRPCClient/private/GRPCHost.h b/src/objective-c/GRPCClient/private/GRPCHost.h
index 6b4f98746d..69a115e88c 100644
--- a/src/objective-c/GRPCClient/private/GRPCHost.h
+++ b/src/objective-c/GRPCClient/private/GRPCHost.h
@@ -39,6 +39,7 @@ struct grpc_call;
 @interface GRPCHost : NSObject
 
 @property(nonatomic, readonly) NSString *address;
+@property(nonatomic, copy) NSString *userAgentPrefix;
 
 /** The following properties should only be modified for testing: */
 
diff --git a/src/objective-c/GRPCClient/private/GRPCHost.m b/src/objective-c/GRPCClient/private/GRPCHost.m
index a8cd3a0e74..f750841a44 100644
--- a/src/objective-c/GRPCClient/private/GRPCHost.m
+++ b/src/objective-c/GRPCClient/private/GRPCHost.m
@@ -34,11 +34,15 @@
 #import "GRPCHost.h"
 
 #include <grpc/grpc.h>
+#import <GRPCClient/GRPCCall+ChannelArg.h>
 
 #import "GRPCChannel.h"
 #import "GRPCCompletionQueue.h"
-#import "GRPCSecureChannel.h"
-#import "GRPCUnsecuredChannel.h"
+#import "NSDictionary+GRPC.h"
+
+// TODO(jcanizales): Generate the version in a standalone header, from templates. Like
+// templates/src/core/surface/version.c.template .
+#define GRPC_OBJC_VERSION_STRING @"0.13.0"
 
 @interface GRPCHost ()
 // TODO(mlumish): Investigate whether caching channels with strong links is a good idea.
@@ -106,13 +110,28 @@
 - (GRPCChannel *)channel {
   // Create it lazily, because we don't want to open a connection just because someone is
   // configuring a host.
+
   if (!_channel) {
+    NSMutableDictionary *args = [NSMutableDictionary dictionary];
+
+    // TODO(jcanizales): Add OS and device information (see
+    // https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#user-agents ).
+    NSString *userAgent = @"grpc-objc/" GRPC_OBJC_VERSION_STRING;
+    if (_userAgentPrefix) {
+      userAgent = [@[_userAgentPrefix, userAgent] componentsJoinedByString:@" "];
+    }
+    args[@GRPC_ARG_PRIMARY_USER_AGENT_STRING] = userAgent;
+
     if (_secure) {
-      _channel = [[GRPCSecureChannel alloc] initWithHost:_address
-                                      pathToCertificates:_pathToCertificates
-                                        hostNameOverride:_hostNameOverride];
+      if (_hostNameOverride) {
+        args[@GRPC_SSL_TARGET_NAME_OVERRIDE_ARG] = _hostNameOverride;
+      }
+
+      _channel = [GRPCChannel secureChannelWithHost:_address
+                                 pathToCertificates:_pathToCertificates
+                                        channelArgs:args];
     } else {
-      _channel = [[GRPCUnsecuredChannel alloc] initWithHost:_address];
+      _channel = [GRPCChannel insecureChannelWithHost:_address channelArgs:args];
     }
   }
   return _channel;
diff --git a/src/objective-c/GRPCClient/private/GRPCSecureChannel.h b/src/objective-c/GRPCClient/private/GRPCSecureChannel.h
deleted file mode 100644
index b82b9fe35a..0000000000
--- a/src/objective-c/GRPCClient/private/GRPCSecureChannel.h
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- *
- * 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.
- *
- */
-
-#include <grpc/grpc.h>
-
-#import "GRPCChannel.h"
-
-struct grpc_channel_credentials;
-
-@interface GRPCSecureChannel : GRPCChannel
-- (instancetype)initWithHost:(NSString *)host;
-
-/**
- * Only in tests shouldn't pathToCertificates or hostNameOverride be nil. Passing nil for
- * pathToCertificates results in using the default root certificates distributed with the library.
- */
-- (instancetype)initWithHost:(NSString *)host
-          pathToCertificates:(NSString *)path
-            hostNameOverride:(NSString *)hostNameOverride;
-
-/** The passed arguments aren't required to be valid beyond the invocation of this initializer. */
-- (instancetype)initWithHost:(NSString *)host
-                 credentials:(struct grpc_channel_credentials *)credentials
-                        args:(grpc_channel_args *)args NS_DESIGNATED_INITIALIZER;
-@end
diff --git a/src/objective-c/GRPCClient/private/GRPCSecureChannel.m b/src/objective-c/GRPCClient/private/GRPCSecureChannel.m
deleted file mode 100644
index a573c171e9..0000000000
--- a/src/objective-c/GRPCClient/private/GRPCSecureChannel.m
+++ /dev/null
@@ -1,118 +0,0 @@
-/*
- *
- * 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 "GRPCSecureChannel.h"
-
-#include <grpc/grpc_security.h>
-
-// Returns NULL if the file at path couldn't be read. In that case, if errorPtr isn't NULL,
-// *errorPtr will be an object describing what went wrong.
-static grpc_channel_credentials *CertificatesAtPath(NSString *path, NSError **errorPtr) {
-  // Files in PEM format can have non-ASCII characters in their comments (e.g. for the name of the
-  // issuer). Load them as UTF8 and produce an ASCII equivalent.
-  NSString *contentInUTF8 = [NSString stringWithContentsOfFile:path
-                                                     encoding:NSUTF8StringEncoding
-                                                        error:errorPtr];
-  NSData *contentInASCII = [contentInUTF8 dataUsingEncoding:NSASCIIStringEncoding
-                                       allowLossyConversion:YES];
-  if (!contentInASCII.bytes) {
-    // Passing NULL to grpc_ssl_credentials_create produces behavior we don't want, so return.
-    return NULL;
-  }
-  return grpc_ssl_credentials_create(contentInASCII.bytes, NULL, NULL);
-}
-
-@implementation GRPCSecureChannel
-
-- (instancetype)initWithHost:(NSString *)host {
-  return [self initWithHost:host pathToCertificates:nil hostNameOverride:nil];
-}
-
-- (instancetype)initWithHost:(NSString *)host
-          pathToCertificates:(NSString *)path
-            hostNameOverride:(NSString *)hostNameOverride {
-  // Load default SSL certificates once.
-  static grpc_channel_credentials *kDefaultCertificates;
-  static dispatch_once_t loading;
-  dispatch_once(&loading, ^{
-    NSString *defaultPath = @"gRPCCertificates.bundle/roots"; // .pem
-    // Do not use NSBundle.mainBundle, as it's nil for tests of library projects.
-    NSBundle *bundle = [NSBundle bundleForClass:self.class];
-    NSString *path = [bundle pathForResource:defaultPath ofType:@"pem"];
-    NSError *error;
-    kDefaultCertificates = CertificatesAtPath(path, &error);
-    NSAssert(kDefaultCertificates, @"Could not read %@/%@.pem. This file, with the root "
-             "certificates, is needed to establish secure (TLS) connections. Because the file is "
-             "distributed with the gRPC library, this error is usually a sign that the library "
-             "wasn't configured correctly for your project. Error: %@",
-             bundle.bundlePath, defaultPath, error);
-  });
-
-  //TODO(jcanizales): Add NSError** parameter to the initializer.
-  grpc_channel_credentials *certificates = path
-      ? CertificatesAtPath(path, NULL)
-      : kDefaultCertificates;
-  if (!certificates) {
-    return nil;
-  }
-
-  // Ritual to pass the SSL host name override to the C library.
-  grpc_channel_args channelArgs;
-  grpc_arg nameOverrideArg;
-  channelArgs.num_args = 1;
-  channelArgs.args = &nameOverrideArg;
-  nameOverrideArg.type = GRPC_ARG_STRING;
-  nameOverrideArg.key = GRPC_SSL_TARGET_NAME_OVERRIDE_ARG;
-  // Cast const away. Hope C gRPC doesn't modify it!
-  nameOverrideArg.value.string = (char *) hostNameOverride.UTF8String;
-  grpc_channel_args *args = hostNameOverride ? &channelArgs : NULL;
-
-  return [self initWithHost:host credentials:certificates args:args];
-}
-
-- (instancetype)initWithHost:(NSString *)host
-                 credentials:(grpc_channel_credentials *)credentials
-                        args:(grpc_channel_args *)args {
-  return (self = [super
-              initWithChannel:grpc_secure_channel_create(
-                                  credentials, host.UTF8String, args, NULL)]);
-}
-
-// TODO(jcanizales): GRPCSecureChannel and GRPCUnsecuredChannel are just convenience initializers
-// for GRPCChannel. Move them into GRPCChannel, which will make the following unnecessary.
-- (instancetype)initWithChannel:(grpc_channel *)unmanagedChannel {
-  [NSException raise:NSInternalInconsistencyException format:@"use another initializer"];
-  return [self initWithHost:nil]; // silence warnings
-}
-
-@end