Firebase没有检索数据（iOS）

Question

我一直在iOS中第一次使用Firebase。我已成功写入数据的火力点，并像这样组织的：

{ 
"users" : { 
"6ytX7ZLa28MYXX8zm3gawJiOYuY2" : { 
    "-Kmj196aXH9uRXd-bCgB" : { 
    "category" : "Work", 
    "date" : "Jun 16, 1:54 AM ", 
    "place" : "Tampa, Forida", 
    "title" : "make an app" 
    }, 
    "-Kmj1HcNcDb9gD2TTlQB" : { 
    "category" : "Design", 
    "date" : "Jun 18, 12:58 AM ", 
    "place" : "Sarasota", 
    "title" : "Design an app" 
    } 
    } 
} 
} 

目前，我有下面的代码来尝试恢复数据，但它渲染不成功。任何你可以提供的帮助将非常感谢！

TableViewController：

import UIKit 
import Firebase 
import FirebaseDatabase 

class TasksHome: UITableViewController { 

private var databaseHandle: FIRDatabaseHandle! 
var ref: FIRDatabaseReference! 
var user: FIRUser! 
var username: String! 
var items = [Item]() 

override func viewDidLoad() { 
    super.viewDidLoad() 

    user = FIRAuth.auth()?.currentUser 
    username = FIRAuth.auth()?.currentUser?.uid 
    ref = FIRDatabase.database().reference() 
    startObservingDatabase() 

} 

override func didReceiveMemoryWarning() { 
    super.didReceiveMemoryWarning() 

} 



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

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

} 

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { 
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! TasksHomeCell 
    let item = items[indexPath.row] 
    cell.titleLabel.text = item.title 
    cell.categoryLabel.text = item.category 
    cell.placeLabel.text = item.place 
    cell.dateLabel.text = item.date 

    return cell 
} 

override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) { 
    if editingStyle == .delete { 
     let item = items[indexPath.row] 
     item.ref?.removeValue() 
    } 
} 


func startObservingDatabase() { 
    databaseHandle = ref?.child("users").child(self.username).observe(.value, with: { (snapshot) in 

     let userDict = snapshot.value as! [String: Any] 
     let category = userDict["category"] as! String 
     let date = userDict["date"] as! String 
     let title = userDict["title"] as! String 
     let place = userDict["place"] as! String 
     print("category: \(category) date: \(date) title: \(title) place: \(place)") 
    }) 
} 

deinit { 
    ref.child("users/\(self.user.uid)/items").removeObserver(withHandle: databaseHandle) 
} 

} 

项目文件

import Foundation 
import FirebaseDatabase 

class Item { 

var ref: FIRDatabaseReference? 
var title: String? 
var category: String? 
var date: String? 
var place: String? 

init (snapshot: FIRDataSnapshot) { 
    ref = snapshot.ref 

    let data = snapshot.value as! Dictionary<String, String> 
    title = data["title"]! as String 
    category = data["category"]! as String 
    date = data["date"]! as String 
    place = data["place"]! as String 
} 

} 

谢谢大家的帮助！

Answer 1

我怀疑你的uid返回的可选值导致你不能返回值或你的数据库规则。在我确保没有可选项的情况下尝试使用以下解决方案，并使用cancel块检查是否有问题向Firebase进行查询。这是对你的viewDidLoad的修改，不要用这个调用你的startObservingDatabase方法。如果您收到“无法找到用户”，那么问题可能出在您的身份验证上。如果你得到“错误观察值...”，那么问题可能与你的数据库安全验证规则有关，如果它们不是已经存在的，请尝试使它们全部公开，并且看看你是否得到任何回报。如果您没有得到这些解决方案，但您现在可以通过此解决方案获得价值，那么问题可能出在您的Firebase参考中的可选项上。

override func viewDidLoad() { 
    super.viewDidLoad() 

    if let user = FIRAuth.auth()?.currentUser { 
     userId = user.uid 
     let baseRef = FIRDatabase.database().reference() 
     databaseHandle = baseRef.child("users").child(userId).observe(.value, with: { (snapshot) in 
    print("we got a value \(snapshot)") 
    let userDict = snapshot.value as! [String: Any] 
    let category = userDict["category"] as! String 
    let date = userDict["date"] as! String 
    let title = userDict["title"] as! String 
    let place = userDict["place"] as! String 
    print("category: \(category) date: \(date) title: \(title) place: \(place)") 
}, withCancel: { (error) in 
      print("error observing value \(error)") 
     }) 

    } 
    else { 
     print("could not find user") 
    } 

}