遍历Firebase中节点中的所有节点

Posted 2023-03-14

【中文标题】遍历Firebase中节点中的所有节点

【英文标题】：Iterating through all nodes in node in Firebase

【发布时间】：2017-02-07 21:31:20

【问题描述】：

我的示例结构如下所示：

我想将每个项目添加到我创建的项目数组中。所以你可以看到downloadListData函数只能从Apples下载信息，因为我不知道如何在不编写大量代码的情况下同时获取Apples、Bread和Eggs。我正在尝试循环和数组，但它没有用。此外，我正在分析 Internet 上的示例，但没有得到适用于我的应用程序的答案。

ListItem.swift：

import Foundation
import Firebase

struct ListItem
    var name : String!
    var addedBy : String!
    var completed : Bool!

    init(name: String, addedBy: String, completed: Bool)
        self.name = name
        self.addedBy = addedBy
        self.completed = completed
    

我的 ViewController.swift 的一部分：

import UIKit
import Firebase

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource 

    var rootRef : FIRDatabaseReference!
    var listDataRef : FIRDatabaseReference!

    var refHandle: UInt!

    var listItemsDownload = [ListItem]()

    //test vars
    var user : String!

    @IBOutlet weak var plusButton: UIButton!
    @IBOutlet weak var tableView: UITableView!

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

        tableView.delegate = self
        tableView.dataSource = self
        user = "[e-mail]"


        rootRef = FIRDatabase.database().reference()
        listDataRef = rootRef.child("listData")            

        downloadListData()
    

func numberOfSections(in tableView: UITableView) -> Int 
    return 1


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


func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell 
    if let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as? CellData

        print("cellForRowAt")
        let items = listItemsDownload[indexPath.row]
        // testing the tableView            
        cell.nameLabel?.text = items.name

        
        return cell
     else
        print("else")
        return CellData()
    

func downloadListData()
    print(" ### DOWNLOAD ###")
    self.listDataRef.observe(FIRDataEventType.value, with:  snapshot in
        var downloadedName : String!
        var downloadedUser : String!
        var downloadedComplete : Bool!

        if let dict = snapshot.value as? Dictionary<String, Any>
            if let apples = dict["Apples"] as? Dictionary<String, Any>

                if let name = apples["name"] as? String
                    downloadedName = name
                

                if let user = apples["addedBy"] as? String
                    downloadedUser = user
                

                if let completed = apples["completed"] as? Bool
                    downloadedComplete = completed
                

                let item = ListItem(name: downloadedName, addedBy: downloadedUser, completed: downloadedComplete)

                self.listItemsDownload.append(item)

                self.tableView.reloadData()

            
        
    )

所以我可能只需要更改这一行来获得不同的值，而不仅仅是 Apples (if let apples = dict["Apples"] as? Dictionary<String, Any>

【参考方案1】：

只需使用单独的方法，您可以使用不同的键调用，如下所示：

  func downloadListData()
    print(" ### DOWNLOAD ###")
    self.listDataRef.observe(FIRDataEventType.value, with:  snapshot in
        addAllItemsFromSnapshotWithKey(snapshot, key: "Apples")
        addAllItemsFromSnapshotWithKey(snapshot, key: "Bread")
        addAllItemsFromSnapshotWithKey(snapshot, key: "Eggs")
        // You need to reload your table view on the main thread, since it's an asynchronous call to firebase
        DispatchQueue.main.async 
          self.tableView.reloadData()  
        
    )
  

  func addAllItemsFromSnapshotWithKey(_ snapshot: FIRDataSnapshot, key: String) 
    var downloadedName : String!
    var downloadedUser : String!
    var downloadedComplete : Bool!

    if let dict = snapshot.value as? Dictionary<String, Any>
      if let values = dict[key] as? Dictionary<String, Any> 

        if let name = values["name"] as? String
          downloadedName = name
        

        if let user = values["addedBy"] as? String
          downloadedUser = user
        

        if let completed = values["completed"] as? Bool
          downloadedComplete = completed
        

        let item = ListItem(name: downloadedName, addedBy: downloadedUser, completed: downloadedComplete)

        self.listItemsDownload.append(item)

      
    
  

更新以获得更具可扩展性的解决方案。只需遍历所有键

 func downloadListData()
    print(" ### DOWNLOAD ###")
    self.listDataRef.observe(FIRDataEventType.value, with:  snapshot in
      var downloadedName : String!
      var downloadedUser : String!
      var downloadedComplete : Bool!

      if let dict = snapshot.value as? Dictionary<String, Any>

        for key in dict.keys 

          if let values = dict[key] as? Dictionary<String, Any> 

            if let name = values["name"] as? String
              downloadedName = name
            

            if let user = values["addedBy"] as? String
              downloadedUser = user
            

            if let completed = values["completed"] as? Bool
              downloadedComplete = completed
            

            let item = ListItem(name: downloadedName, addedBy: downloadedUser, completed: downloadedComplete)

            self.listItemsDownload.append(item)
          
        
        DispatchQueue.main.async 
          self.tableView.reloadData()
        
      
    )
  

【讨论】：

好的，但是如果我有更多数据呢？这似乎不是一个非常可扩展的解决方案。

更新了我的答案@codddeer123