我正在尝试开发出租车预订等应用程序并将数据存储在Firebase上。
但是，从Firebase查询RideDetail（History）数据时遇到问题。
我想以分页形式获取ride_detail以获得特定的“ customer_id”。
我的Firebase DataStructure：
{ "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”是付款完成后的时间戳。
我想要的响应是：
{ "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 } }
我希望我在orderedBy“ paying_time”查询中传递的特定“ customer_id”的前10条记录。我也想做分页。即在第二次查询调用中，它必须返回11-20条记录，依此类推。
这个问题和评论有一些不同的标准，但让我从高层次解决。
第一个答案是：无法查询Firebase的一个孩子的值，然后再排序。
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（在本例中为所有客户id 4个节点），然后按代码订购。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) } }) }
在此示例中，我们创建了一个RideClass，其中存储了有关游乐设施的一些信息，然后存储了可以用作tableView数据源的游乐设施数组。
然后查询所有客户ID为4的游乐设施。我们有一个循环显示未分类的取回内容，然后显示这个小宝石
self.rideArray.sort { $0.pay_time < $1.pay_time }
它将按pay_time对行驶数组进行排序，从而回答了问题。
但是，假设有100,000个乘车子节点。加载所有这些数据并按代码进行排序可能对内存方面提出挑战。你是做什么？
我们利用复合价值；连同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" } },
然后按正确的顺序读取cust id 4节点中的一些代码
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) } })
有两件事要注意：
必须迭代快照以维护子序列
“ \ uf8ff”是Unicode中很高代码级别的字符-因为它包含所有前面的字符。
