ios - 如何在 Firebase IOS 中搜索值

Question

我的 queryOrdered() 函数遇到问题，我不知道如何处理...

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
        }
    }
}}

在我的数据库的这一部分中，我想通过 .Registration 运行搜索

所以我已将引用设置为 Planes > UId

执行此代码后:

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)")
            }
        }

但出现此消息:

2018-11-27 18:03:54.797824+0100 XXXXXXXXXX[12954:527986] 5.10.0 - [Firebase/Database][I-RDB034028] Using an unspecified index. Your data will be downloaded and filtered on the client. Consider adding ".indexOn": "Registration" at /Planes/BJMhmQzJXldULc5X9Y2WzjFEs9a2 to your security rules for better performance

所以我在 firebase 上添加了这样的规则:

{"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，但是这部分没有任何反应:

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)")

我该如何解决这个问题？

感谢您的帮助。

Answer 1

这里发生了两件事；

1. 索引
2. 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，它基本上是查询性能的提高。为了进行测试，请首先消除该变量，因为它不是问题的原因。暂时将规则重置为默认

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

真正的问题是观察，因为它不够深入，无法获取您想要获取的数据。你错过了“SE”级别。这是重写的内容

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)
      }
}

按照您问题中的编写方式，查询将查询上一级:它期望在 SE 和 ME 节点正下方找到注册节点。但这些节点只包含 autoId 节点。

编辑:

通过扁平化(非规范化)来改变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"