Question

我对queryOrdered()函数有问题，我真的不知道该如何处理...

假设我的数据库结构是：

Planes{
Uid{
    SE{
        AutoID{
            .Auto-Id
            .Picture
            .Registration
            .Type
            .model
        }
        AutoID{
            //Same as first one
        }
    }
    ME{
        AutoID{
            //Same as first one
        }
    }
}}

在数据库的这一部分，我想通过.Registration进行搜索

因此，我已将参考设置为Planes > UId

然后执行以下代码：

var acftPickerSelected = aircrafts[listAcftsPicker.selectedRow(inComponent: 0)]

    if let user = Auth.auth().currentUser{
        // user is connect
        let ref = Database.database().reference()
        let userID = Auth.auth().currentUser?.uid

        let ev = ref.child("Planes").child(userID!)

        ev.queryOrdered(byChild: "Registration").queryEqual(toValue: acftPickerSelected).observeSingleEvent(of: .value) { (snapshot: DataSnapshot) in
            for child in snapshot.children {
                let value = snapshot.value as? NSDictionary

                self.pickerRegi = value?["Registration"] as? String ?? "..unknown.."
                self.stdbPickerType = value?["Type"] as? String ?? "..unknown.."
                self.pickerModel = value?["model"] as? String ?? "..unknown.."

                print("Avion : \(self.pickerRegi) - \(self.pickerModel) - \(self.stdbPickerType)")
            }
        }

但是出现此消息：

2018-11-27 18：03：54.797824 + 0100 XXXXXXXXXX [12954：527986] 5.10.0-[Firebase / Database] [I-RDB034028]使用未指定的索引。您的数据将在客户端上下载并过滤。考虑将/ Planes / BJMhmQzJXldULc5X9Y2WzjFEs9a2上的“ .indexOn”：“注册”添加到安全规则中，以提高性能

所以我一直在Firebase上添加如下规则：

{"rules": {
"Planes":{
  "$uid":{
  ".indexOn": ["Registration"],
    ".write": "$uid === auth.uid",
    ".read": "$uid === auth.uid"
  }
},
".read": true,
".write": true}}

现在错误消息不再出现，但是在此部分中什么也没有发生：

self.pickerRegi = value?["Registration"] as? String ?? "..unknown.."
            self.stdbPickerType = value?["Type"] as? String ?? "..unknown.."
            self.pickerModel = value?["model"] as? String ?? "..unknown.."

            print("Avion : \(self.pickerRegi) - \(self.pickerModel) - \(self.stdbPickerType)")

我该如何解决？

感谢您的帮助。

Answer 1

这里发生了两件事；

indexOn
观察者

，在这种情况下，indexOn不是问题。

indexOn在生产应用程序中最重要，基本上可以提高查询性能。对于测试，请首先消除该变量，因为它不是问题的根源。将规则暂时重置为默认值

{
  "rules": {
    ".read": "auth != null",
    ".write": "auth != null"
  }
}

真正的问题是观察，因为它的深度不足以获取您要获取的数据。您缺少“ SE”级别。这是一个重写

let uidRef = ref.child("Planes").child(userID)
let seRef = uidRef.child("SE") //this is the child node to query
seRef.queryOrdered(byChild: "Registration").queryEqual(toValue: acftPickerSelected)
  .observeSingleEvent(of: .value) { snapshot in
      for child in snapshot.children {
          let childSnap = child as! DataSnapshot
          let dict = childSnap.value as! [String: Any]
          let reg = dict["Registration"] as? String ?? "No Reg"
          let mod = dict["model"] as? String ?? "No Model"
          print(reg, mod)
      }
}

问题的编写方式，该查询将查询下一个级别：它期望直接在SE和ME节点下找到一个Registration节点。但是这些节点仅包含autoId节点。

编辑：

通过展平（去规范化）更改结构也是另一种选择

Planes
   Uid
      AutoID
         .Auto-Id //note, if the is the same as the key, its not needed
         .Picture
         .Registration
         .Type
         .model
         .se_or_me: "SE"
      AutoID
         .Auto-Id
         .Picture
         .Registration
         .Type
         .model
         .se_or_me: "ME"

如何在Firebase IOS中搜索值

1 个答案: