如何在 Swift 中将类类型作为函数参数传递？

Question

下面的代码我该怎么做？

    func setupFetchResultController<AnyNSManagedObject>(entityToFetch: AnyNSManagedObject) {
    let fetchRequest:NSFetchRequest<entityToFetch> = entityToFetch.fetchRequest()
}

它会产生带有错误消息的错误：

使用未声明的类型“entityToFetch”

同样当我尝试了以下代码时

    func setupFetchResultController<AnyNSManagedObject>(entityToFetch: AnyNSManagedObject) {
    let fetchRequest:NSFetchRequest<AnyNSManagedObject> = AnyNSManagedObject.fetchRequest()
}

它还产生了带有错误消息的错误：

类型“AnyNSManagedObject”不符合协议“NSFetchRequestResult”

Answer 1

使用泛型

func setupFetchResultController<T: NSManagedObject>(entityToFetch: T) {
    let fetchRequest = T.fetchRequest()        
}

或

func setupFetchResultController<T: NSManagedObject>(entityToFetch: T) {
    let fetchRequest: NSFetchRequest<NSFetchRequestResult> = T.fetchRequest()
}