ios - 如何在 Swift 的 Firebase 查询中应用多个过滤器？

Question

我正在尝试开发一个应用程序，例如出租车预订并在 Firebase 上存储数据。

但是，我在从 Firebase 查询 RideDetail(History) 数据时遇到问题。

我想以分页形式获取特定“customer_id”的 ride_detail。

我的 Firebase 数据结构:

{
  "ride_details": {
    "NuEoP2WNPwigsbY1FQy9M150131918189233": {
      "customer_id": "tstebwLlf4OCRdWhNKO9XCO08xY2",
      "destination_address": "New Ranip\nNew Ranip\nAhmedabad\nGujarat 380081\nIndia",
      "destination_lang": 72.55924470000001,
      "destination_latg": 23.0930152,
      "discount": "10%",
      "driver_id": "cIyZQIJ7tsdvF1a9KpRrKucF2o62",
      "drop_time": "2017-07-29 09:12:21 +0000",
      "fare": "13.16 Rs.",
      "payment_time": 150149034812771,
      "pickup_time": "2017-07-29 09:10:38 +0000",
      "priceperkm": "10.00 Rs.",
      "ride_confirm_time": "2017-07-29 09:06:21 +0000",
      "source_address": "Vastrapur\nVastrapur\nAhmedabad\nGujarat\nIndia",
      "source_lang": 72.5293244,
      "source_latg": 23.0350073,
      "tax": "10%"
    },
    "RH0oZ0Ypbkur3wJM3HMvM150147833457957": {
      "customer_id": "aYQFbwLlf4OCRdWhNKO9XCO08xY2",
      "destination_address": "Sarovar Park Plaza Hotels and Resorts Private Limted\nNo 1\nSector 10\nCBD Belapur\nWadala West\nWadala\nMumbai\nMaharashtra 400614\nIndia",
      "destination_lang": 72.8561644,
      "destination_latg": 19.0176147,
      "discount": 0,
      "driver_id": "cIyZQIJ7tsdvF1a9KpRrKucF2o62",
      "drop_time": "",
      "fare": 0,
      "payment_time": 150149034812772,
      "pickup_time": "",
      "priceperkm": 0,
      "ride_confirm_time": "2017-07-31 05:18:54 +0000",
      "source_address": "Smokin Joe's Fresh Pizza\nShop No. 2\n3\nGround Floor\nAbhiman II\nWadala West\nThane West\nMumbai\nMaharashtra 400602\nIndia",
      "source_lang": 72.8561644,
      "source_latg": 19.0176147,
      "tax": 0
    }
  }
}

这里的“payment_time”是支付完成的时间戳。

我想要的响应是这样的:

{
    "RH0oZ0Ypbkur3wJM3HMvM150147833457957": {
      "customer_id": "aYQFbwLlf4OCRdWhNKO9XCO08xY2",
      "destination_address": "Sarovar Park Plaza Hotels and Resorts Private Limted\nNo 1\nSector 10\nCBD Belapur\nWadala West\nWadala\nMumbai\nMaharashtra 400614\nIndia",
      "destination_lang": 72.8561644,
      "destination_latg": 19.0176147,
      "discount": 0,
      "driver_id": "cIyZQIJ7tsdvF1a9KpRrKucF2o62",
      "drop_time": "",
      "fare": 0,
      "payment_type": 150149034812772,
      "pickup_time": "",
      "priceperkm": 0,
      "ride_confirm_time": "2017-07-31 05:18:54 +0000",
      "source_address": "Smokin Joe's Fresh Pizza\nShop No. 2\n3\nGround Floor\nAbhiman II\nWadala West\nThane West\nMumbai\nMaharashtra 400602\nIndia",
      "source_lang": 72.8561644,
      "source_latg": 19.0176147,
      "tax": 0
    },
    "1trcf0Ypbkur3wJM3HMvM150147833457957": {
      "customer_id": "aYQFbwLlf4OCRdWhNKO9XCO08xY2",
      "destination_address": "Sarovar Park Plaza Hotels and Resorts Private Limted\nNo 1\nSector 10\nCBD Belapur\nWadala West\nWadala\nMumbai\nMaharashtra 400614\nIndia",
      "destination_lang": 72.8561644,
      "destination_latg": 19.0176147,
      "discount": 0,
      "driver_id": "cIyZQIJ7tsdvF1a9KpRrKucF2o62",
      "drop_time": "",
      "fare": 0,
      "payment_type": 150149034812778,
      "pickup_time": "",
      "priceperkm": 0,
      "ride_confirm_time": "2017-07-31 05:18:54 +0000",
      "source_address": "Smokin Joe's Fresh Pizza\nShop No. 2\n3\nGround Floor\nAbhiman II\nWadala West\nThane West\nMumbai\nMaharashtra 400602\nIndia",
      "source_lang": 72.8561644,
      "source_latg": 19.0176147,
      "tax": 0
    } 
}

我想要在查询中传递的特定“customer_id”的前 10 条记录 orderedBy“payment_time”。我也想做同样的分页。即在第二次查询调用中，它必须返回 11-20 条记录，依此类推。

Answer 1

问题和评论有一些不同的标准，但让我从较高的层面来解决它；

第一个答案是:Firebase 不能查询一个 child 的值，然后由另一个 child 订购。

简单查询函数表示:

let query = ridesRef.queryOrdered(byChild: "cust_id").queryEqual(toValue: "cust id 4")

要完成该任务，请查询所需的子数据，在本例中为所有客户 ID 为 4 的节点，然后在代码中进行订购。这是一个例子

class RideClass {
    var key = ""
    var cust_id = ""
    var pay_time = ""

    init(key: String, cust_id: String, pay_time: String) {
        self.key = key
        self.cust_id = cust_id
        self.pay_time = pay_time
    }
}

var rideArray = [RideClass]()

func populateRideArray() {
    let usersRef = self.ref.child("ride_details")
    let query = usersRef.queryOrdered(byChild: "cust_id").queryEqual(toValue: "cust id 4") 
    query.observeSingleEvent(of: .value, with: { snapshot in 
        for child in snapshot.children {
            let snap = child as! DataSnapshot
            let dict = snap.value as! [String: Any]
            let key = snap.key
            let custId = dict["cust_id"] as! String
            let payTime = dict["pay_time"] as! String
            let ride = RideClass(key: key, cust_id: custId, pay_time: payTime)
            self.rideArray.append(ride)
        }

        for ride in self.rideArray {  //unsorted example
            print(ride.pay_time)
        }

        self.rideArray.sort { $0.pay_time < $1.pay_time } //sort

        for ride in self.rideArray {  //sorted example
            print(ride.pay_time)
        }
    })
}

在这个例子中，我们创建了一个 RideClass 来存储一些关于乘车的信息，然后是一个可以用作 tableView 数据源的乘车数组。

然后查询客户 ID 为 4 的所有游乐设施。我们有一个循环来显示未排序的检索内容，然后是这个小 gem

self.rideArray.sort { $0.pay_time < $1.pay_time }

它按 pay_time 对 ride 数组进行排序，这回答了问题。

但假设有 100,000 个 ride 子节点。加载所有这些数据并在代码中排序可能会挑战内存。你是做什么的？

我们利用复合值(value)；除了 cust_id 和 pay_time 的子节点，我们还包括 id_time。这是一个可能的结构:

  "ride_details" : {
    "ride_0" : {
      "cust_id" : "cust id 4",
      "id_time" : "cust id 4_172200",
      "pay_time" : "172200"
    },
    "ride_1" : {
      "cust_id" : "cust id 2",
      "id_time" : "cust id 2_165500",
      "pay_time" : "165500"
    },
    "ride_2" : {
      "cust_id" : "cust id 1",
      "id_time" : "cust id 1_182300",
      "pay_time" : "182300"
    },
    "ride_3" : {
      "cust_id" : "cust id 3",
      "id_time" : "cust id 3_131800",
      "pay_time" : "131800"
    },
    "ride_4" : {
      "cust_id" : "cust id 4",
      "id_time" : "cust id 4_132200",
      "pay_time" : "132200"
    }
  },

然后是一些代码以正确的顺序读取 cust id 4 节点

    let ridesRef = self.ref.child("ride_details")
    let query = ridesRef.queryOrdered(byChild: "id_time")
                        .queryStarting(atValue: "cust id 4_")
                        .queryEnding(atValue: "cust id 4_\\uf8ff")
    query.observeSingleEvent(of: .value, with: { snapshot in
        for child in snapshot.children {
            let snap = child as! DataSnapshot
            let dict = snap.value as! [String: Any]
            let key = snap.key
            let custId = dict["cust_id"] as! String
            let payTime = dict["pay_time"] as! String
            let ride = RideClass(key: key, cust_id: custId, pay_time: payTime)
            self.rideArray.append(ride)
        }

        for ride in self.rideArray {  //unsorted example
            print(ride.pay_time)
        }
    })

需要注意两点:

必须迭代快照以维护子序列

“\uf8ff”是 Unicode 中代码级别非常高的字符 - 因为它包含所有前面的字符。