不能简单地重新定义一个子类中的常量（毕竟它是一个常量）。您得到的错误是无法覆盖与存储属性。它似乎可以覆盖 var ，但是，当我改变 let someVariable 到 var someVariable 当我在子类中访问它时，我得到了someVariable的不确定的使用（注意 - 不管我使用 override 或不）。

As you say, you cannot simply redefine a constant in a subclass (it is a constant, after all). The error you get is "Cannot override with a stored property". It does appear to be possible to override a var, however, when I change the let someVariable to var someVariable I get "ambiguous use of 'someVariable'" when I access it in the subclass (note - same thing happens whether I use override or not).

最初的顾问建议的最简单的解决方案是使用getter。这真的是一个函数，所以你可以高兴地覆盖它，支持变量将为你管理，如果你不提供一个setter，它将是常数：

The simplest solution, as your initial advisors suggested, is to use a getter. This is really a function, so you can happily override it, the backing variable will be managed for you, and if you don't supply a setter, it will be constant:

class BaseView: UIView {
    var someVariable: Int { get { return 1 } }
    // do some work with someVariable
}

class ExtendedView: BaseView {
    override var someVariable: Int { get { return 2 } }
}

let a = BaseView()
a.someVariable // 1
let b = ExtendedView()
b.someVariable // 2