有人可以解释这个Objective-c语法吗？

Question

我之前没有看过这样的语法。有人可以解释这里发生的事情

- (void)viewDidLoad{
    [super viewDidLoad];

    self.tableView.separatorColor = [UIColor colorWithRed:150/255.0f green:161/255.0f blue:177/255.0f alpha:1.0f];
    self.tableView.delegate = self;
    self.tableView.dataSource = self;
    self.tableView.opaque = NO;
    self.tableView.backgroundColor = [UIColor clearColor];
    self.tableView.tableHeaderView = ({
        UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 0, 60.0f)];
        UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 40, 100, 100)];
        imageView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin;
        imageView.image = [UIImage imageNamed:@"avatar.jpg"];
        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 = YES;

        UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(20, 30, 0, 24)];
        label.text = @"Darren";
        label.font = [UIFont fontWithName:@"HelveticaNeue" size:21];
        label.backgroundColor = [UIColor clearColor];
        label.textColor = [UIColor whiteColor];
        [label sizeToFit];
        label.autoresizingMask = UIViewAutoresizingFlexibleRightMargin;

        //[view addSubview:imageView];
        [view addSubview:label];
        view;
    });
}

分配tableHeaderView时会发生什么？在（{}）括号内创建和配置视图的目的是什么？以及如何将创建的视图分配给tableHeaderView属性？

提前致谢。