Changed iOS object detector async calls to delegates

mediapipe/tasks/ios/vision/object_detector/sources/MPPObjectDetector.mm

@@ -51,6 +51,7 @@ static NSString *const kTaskGraphName = @"mediapipe.tasks.vision.ObjectDetectorG
   /** iOS Vision Task Runner */
   MPPVisionTaskRunner *_visionTaskRunner;
 }
+@property(nonatomic, weak) id<MPPObjectDetectorDelegate> objectDetectorDelegate;
 @end
 
 @implementation MPPObjectDetector
@@ -78,11 +79,15 @@ static NSString *const kTaskGraphName = @"mediapipe.tasks.vision.ObjectDetectorG
 
     PacketsCallback packetsCallback = nullptr;
 
-    if (options.completion) {
+    if (options.objectDetectorDelegate) {
+      _objectDetectorDelegate = options.objectDetectorDelegate;
       packetsCallback = [=](absl::StatusOr<PacketMap> statusOrPackets) {
         NSError *callbackError = nil;
         if (![MPPCommonUtils checkCppError:statusOrPackets.status() toError:&callbackError]) {
-          options.completion(nil, Timestamp::Unset().Value(), callbackError);
+          [_objectDetectorDelegate objectDetector:self
+                     didFinishDetectionWithResult:nil
+                          timestampInMilliseconds:Timestamp::Unset().Value()
+                                            error:callbackError];
           return;
         }
 
@@ -95,10 +100,14 @@ static NSString *const kTaskGraphName = @"mediapipe.tasks.vision.ObjectDetectorG
             objectDetectionResultWithDetectionsPacket:statusOrPackets.value()[kDetectionsStreamName
                                                                                   .cppString]];
 
-        options.completion(result,
+        [_objectDetectorDelegate objectDetector:self
-                           outputPacketMap[kImageOutStreamName.cppString].Timestamp().Value() /
+                   didFinishDetectionWithResult:result
-                               kMicroSecondsPerMilliSecond,
+                        timestampInMilliseconds:outputPacketMap[kImageOutStreamName.cppString]
-                           callbackError);
+                                                    .Timestamp()
+                                                    .Value() /
+                                                kMicroSecondsPerMilliSecond
+                                          error:callbackError];
+      }
     };
   }
 
@@ -111,8 +120,8 @@ static NSString *const kTaskGraphName = @"mediapipe.tasks.vision.ObjectDetectorG
   if (!_visionTaskRunner) {
     return nil;
   }
-  }
+}
-  return self;
+return self;
 }
 
 - (instancetype)initWithModelPath:(NSString *)modelPath error:(NSError **)error {
@@ -224,5 +233,4 @@ static NSString *const kTaskGraphName = @"mediapipe.tasks.vision.ObjectDetectorG
   return [_visionTaskRunner processLiveStreamPacketMap:inputPacketMap.value() error:error];
 }
 
-
 @end

mediapipe/tasks/ios/vision/object_detector/sources/MPPObjectDetectorOptions.h

@@ -20,19 +20,48 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+@class MPPObjectDetector;
+
+/**
+ * This protocol defines an interface for the delegates of `MPPImageClassifier` object to receive
+ * results of performing asynchronous object detection on images
+ * (i.e, when `runningMode` = `MPPRunningModeLiveStream`).
+ *
+ * The delegate of `MPPImageClassifier` must adopt `MPPImageClassifierDelegate` protocol.
+ * The methods in this protocol are optional.
+ * TODO: Add parameter `MPPImage` in the callback.
+ */
+@protocol MPPObjectDetectorDelegate <NSObject>
+@required
+- (void)objectDetector:(MPPObjectDetector *)objectDetector
+    didFinishDetectionWithResult:(nullable MPPObjectDetectionResult *)result
+         timestampInMilliseconds:(NSInteger)timestampInMilliseconds
+                           error:(nullable NSError *)error
+    NS_SWIFT_NAME(objectDetector(_:didFinishDetection:timestampInMilliseconds:error:));
+@end
+
 /** Options for setting up a `MPPObjectDetector`. */
 NS_SWIFT_NAME(ObjectDetectorOptions)
 @interface MPPObjectDetectorOptions : MPPTaskOptions <NSCopying>
 
+/**
+ * Running mode of the object detector task. Defaults to `MPPRunningModeImage`.
+ * `MPPImageClassifier` can be created with one of the following running modes:
+ *  1. `MPPRunningModeImage`: The mode for performing object detection on single image inputs.
+ *  2. `MPPRunningModeVideo`: The mode for performing object detection on the decoded frames of a
+ *      video.
+ *  3. `MPPRunningModeLiveStream`: The mode for performing object detection on a live stream of
+ *      input data, such as from the camera.
+ */
 @property(nonatomic) MPPRunningMode runningMode;
 
 /**
- * The user-defined result callback for processing live stream data. The result callback should only
+ * An object that confirms to `MPPObjectDetectorDelegate` protocol. This object must implement
- * be specified when the running mode is set to the live stream mode.
+ * `objectDetector:didFinishDetectionWithResult:timestampInMilliseconds:error:`
- * TODO: Add parameter `MPPImage` in the callback.
+ * to receive the results of performing asynchronous object detection on images (i.e, when
+ * `runningMode` = `MPPRunningModeLiveStream`).
  */
-@property(nonatomic, copy) void (^completion)
+@property(nonatomic, weak) id<MPPObjectDetectorDelegate> objectDetectorDelegate;
-    (MPPObjectDetectionResult *__nullable result, NSInteger timestampMs, NSError *error);
 
 /**
  * The locale to use for display names specified through the TFLite Model Metadata, if any. Defaults

mediapipe/tasks/ios/vision/object_detector/sources/MPPObjectDetectorOptions.m

@@ -33,7 +33,7 @@
   objectDetectorOptions.categoryDenylist = self.categoryDenylist;
   objectDetectorOptions.categoryAllowlist = self.categoryAllowlist;
   objectDetectorOptions.displayNamesLocale = self.displayNamesLocale;
-  objectDetectorOptions.completion = self.completion;
+  objectDetectorOptions.objectDetectorDelegate = self.objectDetectorDelegate;
 
   return objectDetectorOptions;
 }