A UIAlertController 来自 UIViewController 的子类.因此，UIAlertController 包含一个可以修改的视图.因此，要向警报添加标签，您可以这样做:

A UIAlertController sub-classes from UIViewController. Because of this, a UIAlertController contains a view which can be modified. So, to add a label to the alert, you could do this:

let label = UILabel(frame: CGRect(x: 0, y: 0, width: 50, height: 50))
label.text = "Text"
alert.view.addSubview(label)

但是，您应该记住文档中的说明:

UIAlertController 类旨在按原样使用，而不是支持子类化.此类的视图层次结构是私有的，并且不得修改.

The UIAlertController class is intended to be used as-is and does not support subclassing. The view hierarchy for this class is private and must not be modified.