self reference inside a block, weakSelf and strongSelf

ViewController.m

__weak __typeof__(self) weakSelf = self;
dispatch_group_async(_operationsGroup, _operationsQueue, ^{
  __typeof__(self) strongSelf = weakSelf;
  [strongSelf doSomething];
  [strongSelf doSomethingElse];
});

ViewController.swift

dispatch_async(dispatch_get_main_queue()) { [weak self] in
  if let strongSelf = self {
    strongSelf.doSomething()
    strongSelf.doSomethingElse()
  }
}