如何在Swift中將類類型作為函數參數傳遞？

Question

我該如何做以下代碼？

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

它產生一個錯誤並顯示錯誤消息：

使用未聲明的類型'entityToFetch'

當我嘗試以下代碼時

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

它還產生了一個錯誤，並顯示錯誤消息：

類型“ AnyNSManagedObject”不符合協議“ NSFetchRequestResult”

Answer 1

使用泛型

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

要么

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