Update GRPCUnaryResponseHandler with generics

examples/objective-c/route_guide/ViewControllers.m

@@ -106,6 +106,23 @@ static NSString * const kHostAddress = @"localhost:50051";
 }
 
 - (void)execRequest {
+  void (^handler)(RTGFeature *response, NSError *error) = ^(RTGFeature *response, NSError *error) {
+    // TODO(makdharma): Remove boilerplate by consolidating into one log function.
+    if (response.name.length) {
+      NSString *str =[NSString stringWithFormat:@"%@\nFound feature called %@ at %@.", self.outputLabel.text, response.location, response.name];
+      self.outputLabel.text = str;
+      NSLog(@"Found feature called %@ at %@.", response.name, response.location);
+    } else if (response) {
+      NSString *str =[NSString stringWithFormat:@"%@\nFound no features at %@",  self.outputLabel.text,response.location];
+      self.outputLabel.text = str;
+      NSLog(@"Found no features at %@", response.location);
+    } else {
+      NSString *str =[NSString stringWithFormat:@"%@\nRPC error: %@", self.outputLabel.text, error];
+      self.outputLabel.text = str;
+      NSLog(@"RPC error: %@", error);
+    }
+  };
+
   RTGPoint *point = [RTGPoint message];
   point.latitude = 409146138;
   point.longitude = -746188906;
@@ -115,7 +132,7 @@ static NSString * const kHostAddress = @"localhost:50051";
                                                  callOptions:nil];
   [call start];
   call = [_service getFeatureWithMessage:[RTGPoint message]
-                         responseHandler:self
+                         responseHandler:[[GRPCUnaryResponseHandler alloc] initWithResponseHandler:handler responseDispatchQueue:nil]
                              callOptions:nil];
   [call start];
 

src/objective-c/ProtoRPC/ProtoRPC.h

@@ -74,7 +74,7 @@ NS_ASSUME_NONNULL_BEGIN
  * A convenience class of objects that act as response handlers of calls. Issues
  * response to a single handler when the response is completed.
  */
-@interface GRPCUnaryResponseHandler : NSObject<GRPCProtoResponseHandler>
+@interface GRPCUnaryResponseHandler<ResponseType> : NSObject<GRPCProtoResponseHandler>
 
 /**
  * Creates a responsehandler object with a unary call handler.
@@ -83,7 +83,7 @@ NS_ASSUME_NONNULL_BEGIN
  * responseDispatchQueue: the dispatch queue on which the response handler
  * should be issued. If it's nil, the handler will use the main queue.
  */
-- (nullable instancetype)initWithResponseHandler:(void (^)(GPBMessage *, NSError *))handler
+- (nullable instancetype)initWithResponseHandler:(void (^)(ResponseType, NSError *))handler
                            responseDispatchQueue:(nullable dispatch_queue_t)dispatchQueue;
 
 /** Response headers received during the call. */

src/objective-c/ProtoRPC/ProtoRPC.m

@@ -28,13 +28,13 @@
 #import <RxLibrary/GRXWriter+Transformations.h>
 
 @implementation GRPCUnaryResponseHandler {
-  void (^_responseHandler)(GPBMessage *, NSError *);
+  void (^_responseHandler)(id, NSError *);
   dispatch_queue_t _responseDispatchQueue;
 
   GPBMessage *_message;
 }
 
-- (nullable instancetype)initWithResponseHandler:(void (^)(GPBMessage *, NSError *))handler
+- (nullable instancetype)initWithResponseHandler:(void (^)(id, NSError *))handler
                            responseDispatchQueue:(dispatch_queue_t)dispatchQueue {
   if ((self = [super init])) {
     _responseHandler = handler;