iOS 双层block嵌套的用法

(void)setUpModel{
XXModel *model = [XXModel new];

__weak typeof(self) weakSelf = self;

model.dodoBlock = ^(NSString *title) {

  __strong typeof(self) strongSelf = weakSelf;//第一层
  strongSelf.titleLabel.text = title;
  
  __weak typeof(self) weakSelf2 = strongSelf;
  strongSelf.model.dodoBlock = ^(NSString *title2) {

      __strong typeof(self) strongSelf2 = weakSelf2;//第二层
      strongSelf2.titleLabel.text = title2;
  };

};

self.model = model;
}