NSURLSessionDownloadTask - downloads but ends with error

Question

I am trying to download a pdf file. earlier when i used the completion handler block i was able to see the file in the tmp location. I then wanted to show download progress so i implemented the delegate methods. But i can now see the progress bar working and the file being downloaded. but once the download is complete (bytes written/total bytes = 1) the error delegate is called and there is no file in the tmp location. what am i missing ? below is my code. I have uploaded the project at https://www.dropbox.com/s/vn5zwfwx9izq60a/trydownload.zip

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:nil];
    NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithURL:[NSURL URLWithString:@"http://aayudham.com/URLLoadingSystem.pdf"]];
    [downloadTask resume];

}

-(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
    NSLog(@"%@",[error localizedDescription]);
}
-(void) URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
    dispatch_async(dispatch_get_main_queue(), ^{
        _progressBar.progress = (double)totalBytesWritten/(double)totalBytesExpectedToWrite;
        double value =(double)totalBytesWritten/(double)totalBytesExpectedToWrite;
        NSLog(@"%f",value);
    });
}

-(void) URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes
{

}

-(void) URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
{
       NSError *error;
//getting docs dir path
NSArray * tempArray = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docsDir = [tempArray objectAtIndex:0];

//adding folder path
NSString *appDir = [docsDir stringByAppendingPathComponent:@"/Reader/"];

NSFileManager *fileManager = [NSFileManager defaultManager];

if(![fileManager fileExistsAtPath:appDir])
{
    [fileManager createDirectoryAtPath:appDir withIntermediateDirectories:NO attributes:nil error:&error];
}


BOOL fileCopied = [fileManager moveItemAtPath:[location path] toPath:[appDir stringByAppendingString:@"/demo.pdf"] error:&error];

NSLog(fileCopied ? @"Yes" : @"No");
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

Answer 1

@Rob thank you for your prompt replies and that helped me a lot. Here is my code that worked. Hope it helps someone. I am able to get the actual file name and move the file to my documents directory using the original name.

-(void) URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
{
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSError *error;

    //getting application's document directory path
    NSArray * tempArray = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *docsDir = [tempArray objectAtIndex:0];

    //adding a new folder to the documents directory path
    NSString *appDir = [docsDir stringByAppendingPathComponent:@"/Reader/"];

    //Checking for directory existence and creating if not already exists
    if(![fileManager fileExistsAtPath:appDir])
    {
        [fileManager createDirectoryAtPath:appDir withIntermediateDirectories:NO attributes:nil error:&error];
    }

    //retrieving the filename from the response and appending it again to the path
    //this path "appDir" will be used as the target path 
    appDir =  [appDir stringByAppendingFormat:@"/%@",[[downloadTask response] suggestedFilename]];

    //checking for file existence and deleting if already present.
    if([fileManager fileExistsAtPath:appDir])
    {
        NSLog([fileManager removeItemAtPath:appDir error:&error]?@"deleted":@"not deleted");
    }

    //moving the file from temp location to app's own directory
    BOOL fileCopied = [fileManager moveItemAtPath:[location path] toPath:appDir error:&error];
    NSLog(fileCopied ? @"Yes" : @"No");

}