How can I SIMPLY perform two tasks at once in my iPhone app? (threading?)

Question

The Situation:
Somewhere in my app I start downloading data from my server. Before downloading starts, I would like to update a UILabel to say @"Now Downloading...". And set it back to blank when downloading is over.

The Problem:
It seems like the download takes up all of the computers attention, and the UILabel never gets updated until the very end (at which downloading is already over) and so is set back to blank (or, never-visible in real time).

Question:
How can I SIMPLY update my UILabel to say "Now Downloading" just before the download?

Answer 1

If you use NSURLRequest -> NSURLConnection and the NSURLConnection's delegate methods this will perform the download in the background and will notify the delegate of incoming data. This will also allow you to display a progress.

Answer 2

label.text = @"Downloading";
NSOperationQueue *operationQueue = [[NSOperationQueue]alloc]init];
NSInvocationOperation *operation = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(download) object:@"http://www.google.com"];
[operationQueue addOperation:operation];
[operation release];


- (void)download:(NSString *)url
{
    // do the download
    [self performSelectorOnMainThread:@selector(didFinishDownload) withObject:nil waitUntilDone:NO];
}

- (void)didFinishDownload
{
   label.text = @"";
}