Background download JSON

gistfile1.txt

- (void) loadJSON:(NSURL*)url
{
	dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        
		NSData* data = [NSData dataWithContentsOfURL:url];
        
		[self performSelectorOnMainThread:@selector(fetchedData:)
				       withObject:data
			      	    waitUntilDone:YES];
	});
}
 
- (void) fetchedData:(NSData *)data
{
	if(data == nil)
	{
		NSLog(@"Handle JSON download error");
		return;
	}
    
	NSError *error = nil;
	id json = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];
 
	if(!error)
	{
		// Process JSON
	}
}