Swift:如何检查反射中的泛型类型？

Question

我有以下模型:

class BaseClass { ... }
class WeakCollection<T: BaseClass> { ... }
class Person : BaseClass { ... }

class Parent : Person { 
    var children: [Child]
    ...
}

class Child : Person { 
    var parents: WeakCollection<Parent>
    ...
}

let aChild = Child()
...

我正在使用这样的反射:

let mirrored_object = Mirror(reflecting: aChild)
for attr in mirrored_object.children {
    switch attr.value {
         case is Int:
             ...

         case is String:
             ...

         case is WeakCollection<BaseClass>:
             ...
    }
}

问题是检查case is WeakCollection<BaseClass>如果泛型类型不直接是 BaseClass，则始终为 false本身，也就是说，如果它是它的某些子类，则此检查将是错误的。如何检查通用类型？

Answer 1

一个粗略的方法是让你的“WeakCollection”继承自某种协议(protocol):

protocol BaseProtocol {}
class WeakCollection<T> : BaseProtocol

然后在你的开关中这样做:

switch attr.value {
    case is String:
        // This is a string
        break
    case let optionalObject as Optional<Any>:
        if case .some(let complexObject) = optionalObject
        {
            if (complexObject is BaseProtocol)
            {
                // This is a "WeakCollection" kind
            }
        }
        break
}

这有点粗糙，但它给出了你想要的输出。