请教一个有关iOS的问题~百思不得其解

我最近看ios代码，纯新手，遇到一个问题，如下代码中，在给一个table添加tableHeader时，为什么可以直接赋值为（{"添加代码"}）这样的形式呢？我完全不懂这样的形式是什么意思？而且代码最后也不是return view;而是直接写view;

谢谢各位大神了 ~~

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;
    });