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iOS GCD结合AFNetworking异步下载

- (void)downloadImages {

    NSString *fileDir = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).lastObject;

//                         stringByAppendingPathComponent:@"image"];

 

    dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    _imgGroup = dispatch_group_create();

    

    NSLog(@"start downloading");

    

    dispatch_group_async(_imgGroup, globalQueue, ^{

        dispatch_group_enter(_imgGroup);

        

        NSString *filePath = [fileDir stringByAppendingPathComponent:@"image0.jpg"];

        [self downloadImageToPath:filePath url:self.imgURLs[0]];

    });

    

    dispatch_group_async(_imgGroup, globalQueue, ^{

        dispatch_group_enter(_imgGroup);

        

        NSString *filePath = [fileDir stringByAppendingPathComponent:@"image1.jpg"];

        [self downloadImageToPath:filePath url:self.imgURLs[1]];

    });

    

    dispatch_group_async(_imgGroup, globalQueue, ^{

        dispatch_group_enter(_imgGroup);

        

        NSString *filePath = [fileDir stringByAppendingPathComponent:@"image2.jpg"];

        [self downloadImageToPath:filePath url:self.imgURLs[2]];

    });

    

    dispatch_group_notify(_imgGroup, globalQueue, ^{

        NSLog(@"finish download");

    });

}

 

- (void)downloadImageToPath:(NSString *)filePath url:(NSString *)url{

    AFURLSessionManager *sessionMgr = [[AFURLSessionManager alloc] initWithSessionConfiguration:self.sessionConfig];

    NSURL *imgURL = [NSURL URLWithString:url];

    NSURLRequest *request = [NSURLRequest requestWithURL:imgURL];

    

    NSURLSessionDownloadTask *downloadTask =

    [sessionMgr downloadTaskWithRequest:request

                               progress:nil

                            destination:^NSURL * _Nonnull(NSURL * _Nonnull targetPath, NSURLResponse * _Nonnull response) {

                                

                                NSURL *documentURL = [NSURL fileURLWithPath:filePath];

                                return documentURL;

                            } completionHandler:^(NSURLResponse * _Nonnull response, NSURL * _Nullable filePath, NSError * _Nullable error) {

                                

                                dispatch_group_leave(_imgGroup);

                            }];

    

    [downloadTask resume];

 

}

 

iOS GCD结合AFNetworking异步下载