Update the Example and Test case about URLSessionMetrics, expose the API in UIVIew+WebCache to make it easy to write code (or user have to write NSStringFromClass)

Examples/SDWebImage Demo/MasterViewController.m

@@ -113,10 +113,22 @@
     }
     
     cell.customTextLabel.text = [NSString stringWithFormat:@"Image #%ld", (long)indexPath.row];
-    [cell.customImageView sd_setImageWithURL:[NSURL URLWithString:self.objects[indexPath.row]]
+    __weak SDAnimatedImageView *imageView = cell.customImageView;
+    [imageView sd_setImageWithURL:[NSURL URLWithString:self.objects[indexPath.row]]
                  placeholderImage:placeholderImage
                           options:indexPath.row == 0 ? SDWebImageRefreshCached : 0
-                                     context:@{SDWebImageContextImageThumbnailPixelSize : @(CGSizeMake(180, 120))}];
+                          context:@{SDWebImageContextImageThumbnailPixelSize : @(CGSizeMake(180, 120))}
+                         progress:nil
+                        completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
+        SDWebImageCombinedOperation *operation = [imageView sd_imageLoadOperationForKey:imageView.sd_latestOperationKey];
+        SDWebImageDownloadToken *token = operation.loaderOperation;
+        if (@available(iOS 10.0, *)) {
+            NSURLSessionTaskMetrics *metrics = token.metrics;
+            if (metrics) {
+                printf("Metrics: %s download in (%f) seconds\n", [imageURL.absoluteString cStringUsingEncoding:NSUTF8StringEncoding], metrics.taskInterval.duration);
+            }
+        }
+    }];
     return cell;
 }
 

SDWebImage/Core/UIView+WebCache.h

@@ -31,6 +31,13 @@ typedef void(^SDSetImageBlock)(UIImage * _Nullable image, NSData * _Nullable ima
  */
 @property (nonatomic, strong, readonly, nullable) NSURL *sd_imageURL;
 
+/**
+ * Get the current image operation key. Operation key is used to identify the different queries for one view instance (like UIButton).
+ * See more about this in `SDWebImageContextSetImageOperationKey`.
+ * @note You can use method `UIView+WebCacheOperation` to invesigate different queries' operation.
+ */
+@property (nonatomic, strong, readonly, nullable) NSString *sd_latestOperationKey;
+
 /**
  * The current image loading progress associated to the view. The unit count is the received size and excepted size of download.
  * The `totalUnitCount` and `completedUnitCount` will be reset to 0 after a new image loading start (change from current queue). And they will be set to `SDWebImageProgressUnitCountUnknown` if the progressBlock not been called but the image loading success to mark the progress finished (change from main queue).

Tests/Tests/SDWebImageDownloaderTests.m

@@ -642,6 +642,37 @@
     }];
 }
 
+- (void)test26DownloadURLSessionMetrics {
+    XCTestExpectation *expectation1 = [self expectationWithDescription:@"Download URLSessionMetrics works"];
+    
+    SDWebImageDownloader *downloader = [[SDWebImageDownloader alloc] init];
+    
+    __block SDWebImageDownloadToken *token;
+    token = [downloader downloadImageWithURL:[NSURL URLWithString:kTestJPEGURL] completed:^(UIImage * _Nullable image, NSData * _Nullable data, NSError * _Nullable error, BOOL finished) {
+        expect(error).beNil();
+        if (@available(iOS 10.0, tvOS 10.0, macOS 10.12, *)) {
+            NSURLSessionTaskMetrics *metrics = token.metrics;
+            expect(metrics).notTo.beNil();
+            expect(metrics.redirectCount).equal(0);
+            expect(metrics.transactionMetrics.count).equal(1);
+            NSURLSessionTaskTransactionMetrics *metric = metrics.transactionMetrics.firstObject;
+            // Metrcis Test
+            expect(metric.fetchStartDate).notTo.beNil();
+            expect(metric.connectStartDate).notTo.beNil();
+            expect(metric.connectEndDate).notTo.beNil();
+            expect(metric.networkProtocolName).equal(@"http/1.1");
+            expect(metric.resourceFetchType).equal(NSURLSessionTaskMetricsResourceFetchTypeNetworkLoad);
+            expect(metric.isProxyConnection).beFalsy();
+            expect(metric.isReusedConnection).beFalsy();
+        }
+        [expectation1 fulfill];
+    }];
+    
+    [self waitForExpectationsWithCommonTimeoutUsingHandler:^(NSError * _Nullable error) {
+        [downloader invalidateSessionAndCancel:YES];
+    }];
+}
+
 #pragma mark - SDWebImageLoader
 - (void)test30CustomImageLoaderWorks {
     XCTestExpectation *expectation = [self expectationWithDescription:@"Custom image not works"];