ios - NSNotification 用户信息在按下按钮时保持堆叠

Question

所以我有两个 View Controller ，它们同时显示。目标如下:当我按下菜单时，它会返回一个索引。这将通知其他屏幕它需要更新。

我正在做以下事情:

Controller A(菜单)

   func carbonTabSwipeNavigation(carbonTabSwipeNavigation: CarbonTabSwipeNavigation, didMoveAtIndex index: UInt) {
    //NSLog("Did move at index: %ld", index)
        //NSNotification to send data
        NSNotificationCenter.defaultCenter().postNotificationName(NotificationNames.GetIndexCarbonKit, object: nil, userInfo: ["clickedIndex" : Int(index)])
}

Controller B(接收器)

override func viewWillAppear(animated: Bool) {
    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(SearchResults.didReceiveNotification(_:)), name: NotificationNames.GetIndexCarbonKit, object: nil)
}


func didReceiveNotification(notification: NSNotification) {
    let index:Dictionary<String,Int> = notification.userInfo as! Dictionary<String,Int>
    let messageFromNotification = index["clickedIndex"]
    print(" SearchResults now shows index: \(messageFromNotification)")
}

我的问题如下:我将索引从 A 发送到 B 的词典不断堆叠。因此，如果我多次按下菜单，我的输出如下:

 SearchResults now shows index: Optional(0)
 SearchResults now shows index: Optional(1)
 SearchResults now shows index: Optional(1)
 SearchResults now shows index: Optional(2)
 SearchResults now shows index: Optional(2)
 SearchResults now shows index: Optional(2)
 SearchResults now shows index: Optional(3)
 SearchResults now shows index: Optional(3)
 SearchResults now shows index: Optional(3)
 SearchResults now shows index: Optional(3)
 SearchResults now shows index: Optional(1)
 SearchResults now shows index: Optional(1)
 SearchResults now shows index: Optional(1)
 SearchResults now shows index: Optional(1)
 SearchResults now shows index: Optional(1)

如何只获取最后一个索引？我不需要一堆其他的。

Answer 1

自己找到了正确答案。显然，我所要做的就是将 NotificationCenter 添加到 ViewWillAppear，并在 ViewWillDisappear 处将其删除。当我在 View 之间切换菜单时(相同 View 的 4 倍)，它只返回一个值。

override func viewWillAppear(animated: Bool) {
    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(SearchResults.didReceiveNotification(_:)), name: NotificationNames.GetIndexCarbonKit, object: nil)
}

override func viewWillDisappear(animated: Bool) {
    NSNotificationCenter.defaultCenter().removeObserver(self)
}

func didReceiveNotification(notification: NSNotification) {
    let index:Dictionary<String,Int> = notification.userInfo as! Dictionary<String,Int>
    self.currentIndex = (index.first?.1)!
    print(currentIndex)
}