Retaining self with nested blocks?

Question

With the following code:

@interface MyClass()
{
   NSMutableArray * dataArray;
}
@end

@implementation MyClass

- (void) doSomething
{
    __typeof__(self) __weak wself = self;
    dispatch_async(dispatch_get_global_queue(0,0), ^{
       __typeof__(self) sself = wself;
       [sself->dataArray addObject: @"Hello World"];

       dispatch_async(dispatch_get_main_queue(), ^{
         [NSThread sleepForTimeInterval: 30];

         UIAlertView *alert = [[UIAlertView alloc] initWithTitle: sself->dataArray[0] 
                                                         message: @"Message"
                                                        delegate: nil
                                               cancelButtonTitle: @"OK"
                                               otherButtonTitles: nil];
         [alert show];
       });
    });
}

@end

1. Is this the proper way to access sself from within the main queue block?
2. Would sself go out of scope once the initial queue finished?
3. Should I add a second __typeof__(self) sself = wself; inside the main queue block?

Answer 1

1. Yes, sure it is.
2. No, you'll be able to use in main_queue block.
3. No, you don't have to. You don't have to add __typeof__(self) sself = wself; even in global_queue block; it's not necessary, you already have a weakened self object wself (moreover, you will retain self in __typeof__(self) part inside the block).
4. You don't have to use __typeof__. Use simply typeof(self)