在背景线程中处理数据

我写了一方法如下：

- (BOOL)shouldDoSomeWork {
   BOOL result = // here I need do hard work with data in background thread and return result, so main thread should wait until the data is calculated and then return result;
   return result;
}

如何实现？

-(void) startWork
{ 

    [NSThread detachNewThreadSelector:@selector(doSomeWork) toTarget:self withObject:nil];
}

-(void) doSomeWork
{
    NSAutoreleasePool *pool = [NSAutoreleasePool new];

    [pool release];
    [self performSelectorOnMainThread:@selector(doneWork) withObject:nil waitUntilDone:NO];
}  

-(void) doneWork
{

}