我正在尝试开发像出租车预订这样的应用程序并在 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”是付款完成时的时间戳。
我想要的回应是这样的：
{
"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
}
}
我想要特定“customer_id”的前 10 条记录，这些记录是我在orderedBy“ payment_time”查询中传递的。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。
问题和评论有一些不同的标准，但让我在高层次上解决它；
第一个答案是：Firebase 不能查询一个孩子的值，然后由另一个孩子订购。
简单查询功能表示：
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，在本例中是所有客户 id 4 的节点，然后在代码中进行排序。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)
}
})
}
在此示例中，我们创建一个 RideClass 来存储一些有关行程的信息，然后创建一个可用作 tableView 数据源的行程数组。
然后查询 cust id 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，然后是这个小宝石
self.rideArray.sort { $0.pay_time < $1.pay_time }
按 pay_time 对乘车数组进行排序，这回答了问题。
假设有 100,000 个骑行子节点。加载所有这些数据并在代码中排序可能对内存来说是一个挑战。你做什么？
我们利用复合价值；除了 cust_id 和 pay_time 的子节点之外，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"
}
},
然后一些代码以正确的顺序读取 cust id 4 个节点
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)
}
})
有两点需要注意：
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。
编辑：2024-06
You may need to use "\u{F8FF}" instead of "\\uf8ff"
有两种基本方法可能适合您的要求：
构造一个按
payment_timequeryStartingAtValue设置一个 Firebase 云函数，其中数据库触发器监听
payment_timecustomer_ride_details/{{customer_id}}/{{ride_id}}payment_time