iOS 直接加载xib文件到ViewController中

   xib 把它简单理解为一个View

 NSArray *nibContents = [[NSBundle mainBundle] loadNibNamed:@"PubTipView" owner:nil options:nil];
    UIView *plainView = [nibContents lastObject];
    
    //CGSize padding = (CGSize){ 22.0, 22.0 };
    //plainView.frame = (CGRect){padding.width, padding.height, plainView.frame.size};
    
    [self.view addSubview:plainView];