Swift:在 Firebase 数据库中搜索特定值并查找所有关联数据

Question

我有数据上传到我的数据库。我正在尝试实现搜索功能，我可以通过名称搜索某些内容，如果找到该名称，则使用与该名称对应的数据自动填充文本字段。例如，如果我搜索“Pepsi Max”，我想在我的数据库中找到 pepsi max，然后显示价格/位置/评级等。

我目前有一个搜索功能，但它只搜索整个数据库并打印所有值。

func searchT() {

    let pub = pubName.text

    print(pub)


    let databaseRef = Database.database().reference().child("Drinks")
    let query = databaseRef.queryOrdered(byChild: "pub").queryStarting(atValue: pub).queryEnding(atValue: "\(String(describing: pub))\\uf8ff")

    query.observeSingleEvent(of: .value) { (snapshot) in
        guard snapshot.exists() != false else { return }
        print(snapshot.value as Any)
        DispatchQueue.main.async {

            guard let dict = snapshot.value as? [String:Any] else {
                print(snapshot)
                return
            }

            let pubName = dict["pub"] as? String
            let pubLocation = dict["location"] as? String
            let price = dict["price"] as? String
            let rating = dict["rating"] as? String
            let comment = dict["comment"] as? String

            self.pubName.text?.append(pubName!)
            self.pubLocation.text?.append(pubLocation!)
            self.price.text?.append(price!)
            self.rating.text?.append(rating!)
            self.comment.text?.append(comment!)

        }
    }
}

您会注意到，在这个函数中，我正在搜索数据“pubName”(我认为我在第一行中设置不正确，但不确定如何更正它)。此函数在将 textViews 设置为值的第一行崩溃，因为存在“展开可选值时为零”

如何通过 pubName 搜索，找到相应的值，然后将文本字段设置为数据库中与搜索值相关的剩余数据。

提前致谢，E

Answer 1

<强>1。实时数据库

由于您没有包含数据库的结构，我假设您的饮料数据库结构如下:

Screenshot of my Realtime database for this answer

{
  "Drinks" : {
    "-LYiUHm4vtrB3LqCBxEc" : {
      "location" : "toronto",
      "name" : "pepsi max",
      "price" : 13.5,
      "rating" : 3.6
    },
    "-LYiUHm5Lgt3-LENTdBZ" : {
      "location" : "new york",
      "name" : "diet coke",
      "price" : 15.45,
      "rating" : 5
    },
    "-LYiUHm5Lgt3-LENTdB_" : {
      "location" : "chicago",
      "name" : "mountain dew",
      "price" : 2,
      "rating" : 2
    },
    "-LYiUHm5Lgt3-LENTdBa" : {
      "location" : "vancouver",
      "name" : "sprite",
      "price" : 6.98,
      "rating" : 4.5
    }
  }
}

<强>2。 swift 4.0

现在，要按名称搜索任何饮料，请使用以下代码:

func search(drinkName: String) {
        let databaseRef = Database.database().reference().child("Drinks")
        let query = databaseRef.queryOrdered(byChild: "name").queryStarting(atValue: drinkName).queryEnding(atValue: "\(drinkName)\\uf8ff")

        query.observeSingleEvent(of: .value) { (snapshot) in
            guard snapshot.exists() != false else { return }
            //print(snapshot.value)
            DispatchQueue.main.async {
                // Update TextFields here
            }
        }
}

The \uf8ff character used in the query above is a very high code point in the Unicode range. Because it is after most regular characters in Unicode, the query matches all values that start with a b.

来源:https://firebase.google.com/docs/database/rest/retrieve-data

Note: queryOrderedByChild() is case-sensitive. It is nice practice to save all fields lowercased in database as this makes it easier to query data. You can always format strings in front end.

<强>3。将“.indexOn”添加到实时数据库的规则中

为了上述查询工作并获得更好的性能，您需要在要搜索的字段上设置索引。您可以通过转到“规则”选项卡并添加如下索引来执行此操作:

{
  "rules": {
    ".read": true,
    ".write": true,
      "Drinks": {
        ".indexOn": "name"
      }
  }
}

来源:More information on indexing data

更新问题的更新答案:

func searchT() {
        // You must cast pub variable as String.
        guard let pub: String = pubName.text else { return }

        print(pub)


        let databaseRef = Database.database().reference().child("Drinks")

        let query = databaseRef.queryOrdered(byChild: "pub").queryStarting(atValue: pub).queryEnding(atValue: "\(String(describing: pub))\\uf8ff")

        query.observeSingleEvent(of: .value) { (snapshot) in
            guard snapshot.exists() != false else {
                print("failing here")
                return }
            print(snapshot.value as Any)
            DispatchQueue.main.async {

                guard let dict = snapshot.value as? [String:Any] else {
                    print(snapshot)
                    return
                }

                let pubName = dict["pub"] as? String
                let pubLocation = dict["location"] as? String
                let price = dict["price"] as? String
                let rating = dict["rating"] as? String
                let comment = dict["comment"] as? String
            }
        }
    }