DFImageManager now guarantees that completion block will always be ca…

…lled (even if the request was cancelled)

DFImageManager/Source/Core/Managing/DFImageManager.h

@@ -25,7 +25,6 @@
 
 @class DFImageManagerConfiguration;
 
-
 /*! The DFImageManager and the related classes provides an implementation of the DFImageManaging protocol. The role of the DFImageManager is to manage the execution of image requests by delegating the actual job to a classes, implementing DFImageFetching, DFImageCaching, and DFImageProcessing protocols.
  
  @note Completion Block

DFImageManager/Source/Core/Managing/DFImageManager.m

@@ -708,6 +708,11 @@ - (void)_cancelRequestWithHandler:(_DFImageHandler *)handler {
     _DFImageManagerTask *task = handler.task;
     if ([task.handlers containsObject:handler]) {
         [task removeHandler:handler];
+        if (handler.completionHandler) {
+            dispatch_async(dispatch_get_main_queue(), ^{
+                handler.completionHandler(nil, @{ DFImageInfoErrorKey: [NSError errorWithDomain:DFImageManagerErrorDomain code:DFImageManagerErrorCancelled userInfo:nil] });
+            });
+        }
         if (task.handlers.count == 0) {
             [task cancel];
             [self _removeTask:task];

DFImageManager/Source/Core/Support/DFImageManagerDefines.h

@@ -74,3 +74,11 @@ typedef NS_ENUM(NSInteger, DFImageRequestPriority) {
 /*! Progress handler, called on a main thread.
  */
 typedef void (^DFImageRequestProgressHandler)(double progress);
+
+/*! The error domain for DFImageManager.
+ */
+extern NSString *const DFImageManagerErrorDomain;
+
+/*! Returned when an image request is cancelled.
+ */
+static const NSInteger DFImageManagerErrorCancelled = -1;

DFImageManager/Source/Core/Support/DFImageManagerDefines.m

@@ -25,5 +25,6 @@
 NSString *const DFImageInfoRequestIDKey = @"DFImageInfoRequestIDKey";
 NSString *const DFImageInfoErrorKey = @"DFImageInfoErrorKey";
 
-
 CGSize const DFImageMaximumSize = { FLT_MAX, FLT_MAX };
+
+NSString *const DFImageManagerErrorDomain = @"DFImageManagerErrorDomain";

DFImageManager/Source/Core/Support/DFImageRequestID.h

@@ -27,7 +27,7 @@
  */
 @interface DFImageRequestID : NSObject <NSCopying>
 
-/*! Advices the image manager that the request should be cancelled.
+/*! Advices the image manager that the request should be cancelled. The completion block will be called with error value of { DFImageManagerErrorDomain, DFImageManagerErrorCancelled }
  */
 - (void)cancel;
 

DFImageManager/Source/UI/UIImageView+DFImageManager.m

@@ -55,7 +55,9 @@ - (void)df_setImageWithResource:(id)resource targetSize:(CGSize)targetSize conte
     UIImageView *__weak weakSelf = self;
     DFImageRequest *request = [DFImageRequest requestWithResource:resource targetSize:targetSize contentMode:contentMode options:options];
     [[DFImageManager sharedManager] requestImageForRequest:request completion:^(UIImage *image, NSDictionary *info) {
-        weakSelf.image = image;
+        if (image) {
+            weakSelf.image = image;
+        }
     }];
 }
 

DFImageManager/Tests/Tests/TDFImageManager.m

@@ -144,6 +144,21 @@ - (void)testThatCancelsFetchOperationWithTwoHandlers {
     [self waitForExpectationsWithTimeout:3.0 handler:nil];
 }
 
+- (void)testThatCompletionHandlerForCancelledRequestIsCalled {
+    _fetcher.queue.suspended = YES;
+
+    XCTestExpectation *expectation = [self expectationWithDescription:@""];
+    DFImageRequestID *requestID = [_manager requestImageForResource:[TDFMockResource resourceWithID:@"ID01"] completion:^(UIImage *image, NSDictionary *info) {
+        NSError *error = info[DFImageInfoErrorKey];
+        XCTAssertNotNil(error);
+        XCTAssertTrue([error.domain isEqualToString:DFImageManagerErrorDomain]);
+        XCTAssertEqual(error.code, DFImageManagerErrorCancelled);
+        [expectation fulfill];
+    }];
+    [requestID cancel];
+    [self waitForExpectationsWithTimeout:3.0 handler:nil];
+}
+
 #pragma mark - Operation Reuse
 
 - (void)testThatOperationsAreReused {
@@ -325,6 +340,7 @@ - (void)testThatPriorityIsChanged {
         XCTAssertEqual(operation.queuePriority, (NSOperationQueuePriority)DFImageRequestPriorityVeryLow);
         [expectation fulfill];
     }];
+    [NSThread sleepForTimeInterval:0.05]; // Wait till operation is created
     [requestID setPriority:DFImageRequestPriorityVeryLow];
 
     _fetcher.queue.suspended = NO;