如何在 swift 3 中获取此变量的数量？

Question

您好，我正在尝试在 Firebase db 中获取 numOfVids，以便可以在我的 numberOfItemsInSection 中返回该数字。但它返回 0 而不是 6。我知道它返回 0 因为它正在读取空变量而不是 observeSingleEvent 中的变量。

有什么方法可以让我获得修改后的 numOfVids 而不是 为空 numOfVids？

override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    var numOfVids = Int() // 0
    let videosRef = FIRDatabase.database().reference().child("users/\(currentUserID)/videos")

    videosRef.observeSingleEvent(of: .value, with: { (snapshot) in
        //get user value
        numOfVids = Int(snapshot.childrenCount)
        print(numOfVids) //prints 6

    })

    return numOfVids //returns 0
}

提前谢谢你！

Answer 1

试试：-

var numOfVids : Int = 0   
@IBOutlet weak var my_CollectionView: UICollectionView!

override func viewDidLoad() {
    super.viewDidLoad()

    self.my_CollectionView.delegate = self
    self.my_CollectionView.dataSource = self

    loadData { (check) in
        print(check)
    }

}


override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

     // Use only when you want to reload your data every time your view is presented.
         /*
     loadData { (check) in
        print(check)
    }
    */
}

func loadData(completionBlock : @escaping ((_ success : Bool?) -> Void)){

    Database.database().reference().child("your_PATH").observeSingleEvent(of: .value, with: {(Snap ) in

        // Once you have retrieved your data
        // Update the count on the class local variable --  numOfVids
        // Reload your collectionView as ..

        self.my_CollectionView.reloadData()
        completionBlock(true)

  })

override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    return numOfVids

  }

Answer 2

试试这个：

let videosRef = FIRDatabase.database().reference().child("users/\(currentUserID)/videos")

    videosRef.observeSingleEvent(of: DataEventType.value, with: { (snapshot) in
        for data in snapshot.children.allObjects as! [DataSnapshot] {
            if let data = data.value  {

              self.numOfVids = self.numOfVids + 1

            }
        }
        print(numOfVids)
    })

关于变量 numOfVids：

var numOfVids = 0

应该可以了，谢谢