如何在Swift中打开类类型？

Question

我有以下代码：

class Base {}
class A: Base {}
class B: Base {}
class C: Base {}

func next(obj: Base) -> Base {
    if obj is A { return B() }
    else if obj is B { return C() }
    else if obj is C { return A() }
    else { return A() }
}

如何将chained ifs 表示为单个switch语句？

Answer 1

extension Base {

    func next() -> Base {
        switch self {
        case is A: return B()
        case is B: return C()
        case is C: return A()
        default: return A()
        }
    }

}