iOS Memory Warning when downloading many big files

Question

I use the following code to download many files from a server. Some of these files are video files (>60Mo).

This function is called in a loop. It works perfectly with small files...

When I download too many (it depends) big files, I have memory warnings and then application crashes.

Note : the project is ARC

- (bool) copyWebFile:(NSString *)url toFile:(NSString *)toFile ;
{
  NSData *data=[NSData dataWithContentsOfURL:[NSURL URLWithString:url]] ;
  if (data)
  {
    NSError *error ;
    if ([[NSFileManager defaultManager] fileExistsAtPath:toFile])
    {
      NSLog(@"Existant %@", toFile) ;
      [[NSFileManager defaultManager] removeItemAtPath:toFile error:nil] ;
    }
    if ([data writeToFile:toFile options:NSDataWritingAtomic error:&error]==NO)
    {
      NSLog(@"@Error creating file-%@ \n", toFile) ;
      NSLog(@"@Error description-%@ \n", [error localizedDescription]) ;
      NSLog(@"@Error suggestion-%@ \n", [error localizedRecoverySuggestion]) ;
      NSLog(@"Error reason-%@", [error localizedFailureReason]) ;
    }
    else
    {
      return(true) ;
    }
  }
  return(false) ;
}

In my application delegate, I added this code : no difference.

- (void)applicationDidReceiveMemoryWarning:(UIApplication *)application
{
  [[NSURLCache sharedURLCache] removeAllCachedResponses] ;
}

Answer 1

You should write the file directly to disk, without keeping whole file in the memory. One of the easy ways is to create a delegate for NSURLConnection and write received data.

This questions answers how to do that with the code example: How to download files directly to disk on the iPhone os?

Answer 2

Use @autoreleasepool and try like this..

- (bool) copyWebFile:(NSString *)url toFile:(NSString *)toFile ;
    {
        @autoreleasepool
        {
            NSData *data=[NSData dataWithContentsOfURL:[NSURL URLWithString:url]] ;
            if (data)
            {
                NSError *error ;
                if ([[NSFileManager defaultManager] fileExistsAtPath:toFile])
                {
                    NSLog(@"Existant %@", toFile) ;
                    [[NSFileManager defaultManager] removeItemAtPath:toFile error:nil] ;
                }
                if ([data writeToFile:toFile options:NSDataWritingAtomic error:&error]==NO)
                {
                    NSLog(@"@Error creating file-%@ \n", toFile) ;
                    NSLog(@"@Error description-%@ \n", [error localizedDescription]) ;
                    NSLog(@"@Error suggestion-%@ \n", [error localizedRecoverySuggestion]) ;
                    NSLog(@"Error reason-%@", [error localizedFailureReason]) ;
                }
                else
                {
                    return(true) ;
                }
            }
            return(false) ;
        }
    }