OC中的一些编程写法--（{"添加代码"}） 花括号用法

self.tableView.tableHeaderView = ({
        UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 0, 184.0f)];
        UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 40, 100, 100)];
        imageView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin;
        imageView.image = [UIImage imageNamed:@"avatar.png"];
        imageView.layer.masksToBounds = YES;
        imageView.layer.cornerRadius = 50.0;
        imageView.layer.borderColor = [UIColor whiteColor].CGColor;
        imageView.layer.borderWidth = 3.0f;
        imageView.layer.rasterizationScale = [UIScreen mainScreen].scale;
        imageView.layer.shouldRasterize = YES;
        imageView.clipsToBounds = YESS;  
        [view addSubview:imageView];
        view;
    });