Question

我正在运行两组相同的代码，但是，我不明白为什么第二组代码失败。如果我从中更改线 println(result.password)至println(result.token)
我收到'AnyObject' does not have a member named 'token'

的错误

以下是工作代码：

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    var appDel: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
    var context: NSManagedObjectContext = appDel.managedObjectContext!
    var newUser = NSEntityDescription.insertNewObjectForEntityForName("Users", inManagedObjectContext: context) as! NSManagedObject

    newUser.setValue("test-1", forKey: "token")
    context.save(nil)

    var request = NSFetchRequest(entityName: "Users")
    var results = context.executeFetchRequest(request, error: nil)

    if results!.count > 0 {
        for result: AnyObject in results! {
            println(result.password)
        }
    } else {
        println("No results")
    }
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

如果我将行更改为println(result)，我会收到打印输出，显示有一个名为token的属性。

<NSManagedObject: 0x7ffa2945c3a0> (entity: Users; id: 0xd000000000040000 <x-coredata://749CCE65-5C4A-45F2-839C-195A94AFCDB6/Users/p1> ; data: <fault>)
<NSManagedObject: 0x7ffa2945c400> (entity: Users; id: 0xd000000000080000 <x-coredata://749CCE65-5C4A-45F2-839C-195A94AFCDB6/Users/p2> ; data: <fault>)
<NSManagedObject: 0x7ffa2945c460> (entity: Users; id: 0xd0000000000c0000 <x-coredata://749CCE65-5C4A-45F2-839C-195A94AFCDB6/Users/p3> ; data: <fault>)
<NSManagedObject: 0x7ffa2964b360> (entity: Users; id: 0xd000000000100000 <x-coredata://749CCE65-5C4A-45F2-839C-195A94AFCDB6/Users/p4> ; data: {
    password = nil;
    token = "test-1";
    username = nil;
})

Answer 1

即使println(result.password)有效，我也很惊讶问题是result的类型。在for-in-loop中，您明确告诉Swift将result作为AnyObject提供：

for result: AnyObject in results! {
    println(result.password)
}

现在AnyObject没有任何名为token或password的成员。因此，即使您要存储的对象可能属于具有属性的类型，也无法访问这些属性因此，在能够访问这些属性之前，您必须向下转换为所需的类型这可以通过省略: AnyObject来实现，假设results是所需类型的数组。

“AnyObject”没有成员名称 - 访问核心数据时

1 个答案: