NSInputStream with url coming up nil in iOS

Question

I'm trying to set up a NSInputStream, but my input stream is comes out as nil when I step into the code. The url comes from a Dropbox account.

Getting the file through NSData after I have the url through Dropbox Chooser crashes my iPhone 4 (although not when it is running through XCode). The files are just too big, so I wanted to try NSInputStream.

I saw from I cannot initialize a NSInputStream that the url is supposed to be local. Any idea how to stream a file from Dropbox?

Thanks.

- (void)setUpStreamForFile {
// iStream is NSInputStream instance variable already declared
iStream = [NSInputStream inputStreamWithURL:url];
[iStream setDelegate:self];
[iStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
                   forMode:NSDefaultRunLoopMode];
[iStream open];
}

Answer 1

so thanks to rmaddy's suggestion, I looked up NSURLConnection but decided to use the features of NSURLSession instead.

I used the NSURLSessionDownloadTask like this. Familiarity with the Dropbox chooser should help.

-(IBAction)didPressChooser:(id)sender {
{
    [[DBChooser defaultChooser] openChooserForLinkType:DBChooserLinkTypeDirect
                                    fromViewController:self completion:^(NSArray *results)
     {
         if ([results count]) {

             DBChooserResult *_result = results[0];
             NSString *extension = [_result.name pathExtension];
             if ([extension isEqualToString:@"m4a"]) {
                 url = _result.link; //url has already been declared elsewhere
                 DBFileName = _result.name; //DPFileName has also been declared. It's a string

                 NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration];
                 NSURLSession *session = [NSURLSession sessionWithConfiguration: defaultConfigObject delegate:self delegateQueue: [NSOperationQueue mainQueue]];
                NSURLSessionDownloadTask *getFile = [session downloadTaskWithURL:url];
                 [getFile resume];

             }


                   } else {
             // User canceled the action
         }


     }];
}
}

Once you have that, you put in another method that works as the completion handler.

-(void)URLSession:(NSURLSession *)session
 downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location {

NSArray       *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES); //I put the file in a temporary folder here so it doesn't take up too much room.
NSString  *documentsDirectory = [paths objectAtIndex:0];

NSString  *filePath = [NSString stringWithFormat:@"%@/%@", documentsDirectory, DBFileName];
NSData *data = [NSData dataWithContentsOfURL:location];
[data writeToFile:filePath atomically:YES];
url = [NSURL fileURLWithPath:filePath];  //Yep, I needed to re-assign url for use elsewhere.

//do other stuff with your local file now that you have its url!

}

A bonus is that you get to keep track of the download progress with this awesome feature:

-(void)URLSession:(NSURLSession *)session
 downloadTask:(NSURLSessionDownloadTask *)downloadTask
 didWriteData:(int64_t)bytesWritten
totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
NSLog(@"%f / %f", (double)totalBytesWritten,
      (double)totalBytesExpectedToWrite);
}

Anyway, hope someone finds this useful. Works much faster on my iPhone 4 than NSURLSessionDataTask which works in a similar manner.