.tap是用Ruby实现为NSObject类别的方法

示例

    UILabel* label = [[[UILabel alloc] init] tap:^(UILabel* lbl){
        lbl.text = @"Hello";
        lbl.textColor = [UIColor whiteColor];
        lbl.font = [UIFont systemFontOfSize:88];
        lbl.backgroundColor = [UIColor blackColor];
        [lbl sizeToFit];
    }];

    [self.view addSubview:label];