Move OAuth2 provider to GRPCCall+OAuth2

src/objective-c/GRPCClient/GRPCCall+OAuth2.h

@@ -18,6 +18,13 @@
 
 #import "GRPCCall.h"
 
+/**
+ * The protocol of an OAuth2 token object from which GRPCCall can acquire a token.
+ */
+@protocol GRPCAuthorizationProtocol
+- (void)getTokenWithHandler:(void (^)(NSString *token))hander;
+@end
+
 /** Helpers for setting and reading headers compatible with OAuth2. */
 @interface GRPCCall (OAuth2)
 
@@ -33,4 +40,12 @@
 /** Returns the value (if any) of the "www-authenticate" response header (the challenge header). */
 @property(atomic, readonly) NSString *oauth2ChallengeHeader;
 
+/**
+ * The authorization token object to be used when starting the call. If the value is set to nil, no
+ * oauth authentication will be used.
+ *
+ * If tokenProvider exists, it takes precedence over the token set by oauth2AccessToken.
+ */
+@property(atomic, strong) id<GRPCAuthorizationProtocol> tokenProvider;
+
 @end

src/objective-c/GRPCClient/GRPCCall+OAuth2.m

@@ -16,6 +16,8 @@
  *
  */
 
+#import <objc/runtime.h>
+
 #import "GRPCCall+OAuth2.h"
 
 static NSString * const kAuthorizationHeader = @"authorization";
@@ -23,6 +25,7 @@ static NSString * const kBearerPrefix = @"Bearer ";
 static NSString * const kChallengeHeader = @"www-authenticate";
 
 @implementation GRPCCall (OAuth2)
+@dynamic tokenProvider;
 
 - (NSString *)oauth2AccessToken {
   NSString *headerValue = self.requestHeaders[kAuthorizationHeader];
@@ -45,4 +48,12 @@ static NSString * const kChallengeHeader = @"www-authenticate";
   return self.responseHeaders[kChallengeHeader];
 }
 
+- (void)setTokenProvider:(id<GRPCAuthorizationProtocol>)tokenProvider {
+  objc_setAssociatedObject(self, @selector(tokenProvider), tokenProvider, OBJC_ASSOCIATION_RETAIN);
+}
+
+- (id<GRPCAuthorizationProtocol>)tokenProvider {
+  return objc_getAssociatedObject(self, @selector(tokenProvider));
+}
+
 @end

src/objective-c/GRPCClient/GRPCCall.h

@@ -139,13 +139,6 @@ typedef NS_ENUM(NSUInteger, GRPCErrorCode) {
   GRPCErrorCodeDataLoss = 15,
 };
 
-/**
- * The protocol of an OAuth2 token object from which GRPCCall can acquire a token.
- */
-@protocol GRPCAuthorizationProtocol
-- (void)getTokenWithHandler:(void (^)(NSString *token))hander;
-@end
-
 /**
  * Safety remark of a gRPC method as defined in RFC 2616 Section 9.1
  */
@@ -222,14 +215,6 @@ extern id const kGRPCTrailersKey;
  */
 @property(atomic, readonly) NSDictionary *responseTrailers;
 
-/**
- * The authorization token object to be used when starting the call. If the value is set to nil, no 
- * oauth authentication will be used.
- *
- * Not compatible with property oauth2AccessToken in GRPCCall (OAuth2). Do not use both at the same time.
- */
-@property(atomic, strong) id<GRPCAuthorizationProtocol> tokenProvider;
-
 /**
  * The request writer has to write NSData objects into the provided Writeable. The server will
  * receive each of those separately and in order as distinct messages.

src/objective-c/GRPCClient/GRPCCall.m

@@ -18,6 +18,8 @@
 
 #import "GRPCCall.h"
 
+#import "GRPCCall+OAuth2.h"
+
 #include <grpc/grpc.h>
 #include <grpc/support/time.h>
 #import <RxLibrary/GRXConcurrentWriteable.h>