S3TransferManager not able to save file/data on S3GetObjectRequest targetedFilePath in ios

Question

I am an iOS developer using Amazon S3 to upload and download the data. I successfully uploaded many image files, but when I am trying to download those all files, I am not able to save data or file on targeted path of S3GetObjectRequest. I am requesting object through the S3TransferManager.

Below is my code

- (void)listObjects:(id)sender {

    self.collection = [[NSMutableArray alloc] init];

    s3Client = [[AmazonS3Client alloc] initWithAccessKey:ACCESS_KEY_ID withSecretKey:SECRET_KEY];

    @try {

        S3ListObjectsRequest *req = [[S3ListObjectsRequest alloc] initWithName:AMAZON_BUCKET_NAME];
        req.prefix = @"arvinds/8/";
        //req.prefix = [NSString stringWithFormat:@"%@", self.appUser.userEmail];
        S3ListObjectsResponse *resp = [s3Client listObjects:req];

        NSMutableArray* objectSummaries = resp.listObjectsResult.objectSummaries;

        for (int x = 0; x < [objectSummaries count]; x++) {
            NSLog(@"objectSummaries: %@",[objectSummaries objectAtIndex:x]);

            S3ObjectSummary *s3Object = [objectSummaries objectAtIndex:x];

            NSString *downloadingFilePath = [[NSTemporaryDirectory() stringByAppendingPathComponent:@"download"] stringByAppendingPathComponent:s3Object.key];


            NSURL *downloadingFileURL = [NSURL fileURLWithPath:downloadingFilePath];
            NSLog(@"downloadingFilePath--- %@",downloadingFilePath);

            if ([[NSFileManager defaultManager] fileExistsAtPath:downloadingFilePath]) {
                [self.collection addObject:downloadingFileURL];
            } else {

                [self.collection addObject:downloadingFileURL];

                S3GetObjectRequest *getObj = [[S3GetObjectRequest new] initWithKey:s3Object.key withBucket:AMAZON_BUCKET_NAME];
                getObj.targetFilePath = downloadingFilePath;
                getObj.delegate = self;
                [self download:getObj];// Start downloding image and write in default folder
            }
        }
        dispatch_async(dispatch_get_main_queue(), ^{
            [self.GalleryCollectionView reloadData];
            //[self downloadAllRequestObject];
        });
    }
    @catch (NSException *exception) {
        NSLog(@"Cannot list S3 %@",exception);
    }
}


// Above code is for access all the objects stored on Amazon S3 server.

// Below code is for S3TransferManager request
- (void)download:(S3GetObjectRequest *)downloadRequest {
    S3TransferManager *transferManager = [S3TransferManager new];
    transferManager.s3 = s3Client;
    transferManager.delegate = self;
    [transferManager download:downloadRequest]; 
}

When executing this, it is not saving data on the target path.

Answer 1

- download: is an asynchronous method and returns immediately. Since you are not retaining a strong reference to an instance of S3TransferManager, it can be released before the download completes. You need to keep a strong reference to transferManager.

Please note that you are using a deprecated version of the AWS SDK. It may be worthwhile to migrate to the version 2 of the AWS Mobile SDK for iOS. With the latest version of the SDK, you do not need to worry about the memory retention issue you are encountering.