为什么我的对象快速解除分配？

Question

我有一个带有绑定值的NSTextField - 绑定到委托“self.myObject.Title” 运行此代码

@NSApplicationMain

class AppDelegate: NSObject, NSApplicationDelegate {

    @IBOutlet weak var window: NSWindow!

    var myObject = OwnObject()

    func applicationDidFinishLaunching(aNotification: NSNotification) {
        // Insert code here to initialize your application
        myObject = OwnObject()
        print(myObject.Title)
    }

}

class OwnObject: NSObject {

    var Title : String! = ""

    override init() {

        super.init()
        self.Title = "This is a title"

    }
}

将填充TextField的正确标题，但myObject将自动解除分配，我收到此错误

2015-06-16 15:43:55.587 testapp109[7896:463502] An instance 0x60000004d4d0 of class testapp109.OwnObject was deallocated while key value observers were still registered with it. Current observation info: <NSKeyValueObservationInfo 0x6080000538c0> (
<NSKeyValueObservance 0x6080000c3aa0: Observer: 0x6080000c3a30, Key path: Title, Options: <New: NO, Old: NO, Prior: NO> Context: 0x0, Property: 0x608000053890>
)

为什么对象被解除分配，我该如何防止这种情况？ 感谢