Make Objective-C interface use SetDirectionWithError

Also moves implementation of legacy setDirection() without error to the
api/ directory.

This is one step in the plan for changing the API
to return RTCError.

Bug: chromium:980879
Change-Id: Ibce8edf8e3c6d41de7ce49d2ffc33f5b282a0e9f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/181520
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Guido Urdaneta <guidou@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31943}

sdk/objc/api/peerconnection/RTCRtpTransceiver.h

@@ -16,6 +16,8 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+extern NSString *const kRTCRtpTransceiverErrorDomain;
+
 /** https://w3c.github.io/webrtc-pc/#dom-rtcrtptransceiverdirection */
 typedef NS_ENUM(NSInteger, RTCRtpTransceiverDirection) {
   RTCRtpTransceiverDirectionSendRecv,
@@ -98,12 +100,9 @@ RTC_OBJC_EXPORT
 
 /** The direction attribute indicates the preferred direction of this
  *  transceiver, which will be used in calls to createOffer and createAnswer.
- *  An update of directionality does not take effect immediately. Instead,
- *  future calls to createOffer and createAnswer mark the corresponding media
- *  descriptions as sendrecv, sendonly, recvonly, or inactive.
  *  https://w3c.github.io/webrtc-pc/#dom-rtcrtptransceiver-direction
  */
-@property(nonatomic) RTCRtpTransceiverDirection direction;
+@property(nonatomic, readonly) RTCRtpTransceiverDirection direction;
 
 /** The currentDirection attribute indicates the current direction negotiated
  *  for this transceiver. If this transceiver has never been represented in an
@@ -119,6 +118,13 @@ RTC_OBJC_EXPORT
  */
 - (void)stopInternal;
 
+/** An update of directionality does not take effect immediately. Instead,
+ *  future calls to createOffer and createAnswer mark the corresponding media
+ *  descriptions as sendrecv, sendonly, recvonly, or inactive.
+ *  https://w3c.github.io/webrtc-pc/#dom-rtcrtptransceiver-direction
+ */
+- (void)setDirection:(RTCRtpTransceiverDirection)direction error:(NSError **)error;
+
 @end
 
 RTC_OBJC_EXPORT

sdk/objc/api/peerconnection/RTCRtpTransceiver.mm

@@ -17,6 +17,8 @@
 #import "base/RTCLogging.h"
 #import "helpers/NSString+StdString.h"
 
+NSString *const kRTCRtpTransceiverErrorDomain = @"org.webrtc.RTCRtpTranceiver";
+
 @implementation RTC_OBJC_TYPE (RTCRtpTransceiverInit)
 
 @synthesize direction = _direction;
@@ -75,9 +77,18 @@
       rtpTransceiverDirectionFromNativeDirection:_nativeRtpTransceiver->direction()];
 }
 
-- (void)setDirection:(RTCRtpTransceiverDirection)direction {
-  _nativeRtpTransceiver->SetDirection(
+- (void)setDirection:(RTCRtpTransceiverDirection)direction error:(NSError **)error {
+  webrtc::RTCError nativeError = _nativeRtpTransceiver->SetDirectionWithError(
       [RTC_OBJC_TYPE(RTCRtpTransceiver) nativeRtpTransceiverDirectionFromDirection:direction]);
+
+  if (!nativeError.ok() && error) {
+    *error = [NSError errorWithDomain:kRTCRtpTransceiverErrorDomain
+                                 code:static_cast<int>(nativeError.type())
+                             userInfo:@{
+                               @"message" : [NSString stringWithCString:nativeError.message()
+                                                               encoding:NSUTF8StringEncoding]
+                             }];
+  }
 }
 
 - (BOOL)currentDirection:(RTCRtpTransceiverDirection *)currentDirectionOut {