Add logging to the demo app. (#2337)

Summary:
Pull Request resolved: #2337
bypass-github-export-checks

Reviewed By: cccclai

Differential Revision: D54711006

fbshipit-source-id: f1865b36c3a548a06da00d6e02ee1652970d1747

Author: shoumikhin

examples/demo-apps/apple_ios/ExecuTorchDemo/ExecuTorchDemo/Sources/App/ContentView.swift

@@ -33,7 +33,7 @@ struct ContentView: View {
       TopBar(title: "ExecuTorch Demo")
       ClassificationLabelView(controller: classificationController)
       Spacer()
-      ClassificationTimeView(controller: classificationController).hidden()
+      ClassificationTimeView(controller: classificationController)
       ModeSelector(controller: classificationController)
     }
   }

examples/demo-apps/apple_ios/ExecuTorchDemo/ExecuTorchDemo/Sources/MobileNet/MobileNetClassifier.swift

@@ -6,9 +6,12 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+import ExecuTorch
 import ImageClassification
 import UIKit
 
+import os.log
+
 public enum MobileNetClassifierError: Error {
   case inputPointer
   case rawData
@@ -43,6 +46,16 @@ public class MobileNetClassifier: ImageClassification {
     mobileNetClassifier = ETMobileNetClassifier(filePath: modelFilePath)
     rawDataBuffer = [UInt8](repeating: 0, count: Int(Self.cropSize * Self.cropSize) * 4)
     normalizedBuffer = [Float](repeating: 0, count: rawDataBuffer.count / 4 * 3)
+
+    #if DEBUG
+    Log.shared.add(sink: self)
+    #endif
+  }
+
+  deinit {
+    #if DEBUG
+    Log.shared.remove(sink: self)
+    #endif
   }
 
   public func classify(image: UIImage) throws -> [Classification] {
@@ -133,3 +146,24 @@ public class MobileNetClassifier: ImageClassification {
     return expInput.map { $0 / sumExpInput }
   }
 }
+
+#if DEBUG
+extension MobileNetClassifier: LogSink {
+  public func log(level: LogLevel, timestamp: TimeInterval, filename: String, line: UInt, message: String) {
+    let logMessage = "executorch:\(filename):\(line) \(message)"
+
+    switch level {
+    case .debug:
+      os_log(.debug, "%{public}@", logMessage)
+    case .info:
+      os_log(.info, "%{public}@", logMessage)
+    case .error:
+      os_log(.error, "%{public}@", logMessage)
+    case .fatal:
+      os_log(.fault, "%{public}@", logMessage)
+    default:
+      os_log("%{public}@", logMessage)
+    }
+  }
+}
+#endif

extension/apple/ExecuTorch/Exported/ExecuTorchLog.h

@@ -59,14 +59,14 @@ NS_SWIFT_NAME(Log)
  *
  * @param sink The log sink to add.
  */
-- (void)addSink:(id<ExecuTorchLogSink>)sink;
+- (void)addSink:(id<ExecuTorchLogSink>)sink NS_SWIFT_NAME(add(sink:));
 
 /**
  * Removes a previously added log sink.
  *
  * @param sink The log sink to remove.
  */
-- (void)removeSink:(id<ExecuTorchLogSink>)sink;
+- (void)removeSink:(id<ExecuTorchLogSink>)sink NS_SWIFT_NAME(remove(sink:));
 
 + (instancetype)new NS_UNAVAILABLE;
 - (instancetype)init NS_UNAVAILABLE;