ios - 为什么我的 iOS 应用程序无法从 Firebase 数据库读取？

Question

我目前在读取 Firebase 数据库并将其显示到表列表中时遇到麻烦。下面是我在当前 View Controller 中使用的代码。

import UIKit
import Firebase
import FirebaseDatabase

class Buy_1: UIViewController, UITableViewDataSource, 
 UITableViewDelegate   {

var ref: DatabaseReference!
var databaseHandle: DatabaseHandle!

var postItem: [String] = []

@IBOutlet weak var TableView: UITableView!

@IBAction func goBackToOneButtonTapped(_ sender: Any) {
    performSegue(withIdentifier: "unwindSegueToVC1", sender: self)
}

override func viewDidLoad() {
    super.viewDidLoad()

    if FirebaseApp.app() == nil {
        FirebaseApp.configure()
    }

    //Set Self as tableview's data source and delegate
    self.TableView.delegate = self
    self.TableView.dataSource = self

    //Set the firebase reference
    ref = Database.database().reference()

    //Retrieve and listen for changes
    databaseHandle = ref?.child ("items").observe(.childAdded, with: { (snapshot) in

        //Convert value of data into string
        if let item = snapshot.value as? String
        {
            self.postItem.append(item)
            self.TableView.reloadData()
            self.ref?.keepSynced(true)
        }

        /*if let actualItem = item {
            //Appends data to our Item Array
            self.postItem.append(actualItem)

            //Reload TableView
            self.TableView.reloadData()
        }*/

    })
    // Do any additional setup after loading the view.
}


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

/*
// MARK: - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    // Get the new view controller using segue.destinationViewController.
    // Pass the selected object to the new view controller.
}
*/

//MARK: - UITableView Delegate Methods


func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return postItem.count
}

func tableView(_ TableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = TableView.dequeueReusableCell(withIdentifier: "BasicCell", for: indexPath)

    cell.textLabel?.text = postItem[indexPath.row]
    return cell

  }
}

我没有收到代码中的任何错误，所以我不确定出了什么问题。&我已经将数据库规则设置为true。

谢谢。

Answer 1

您正在观察.childAdded，只有当将子项添加到您观察到的数据树时，它才会触发您的 block 。将其更改为 .value。