如何从Firebase逆转项目的顺序 [英] How to reverse order of items from Firebase
本文介绍了如何从Firebase逆转项目的顺序的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
如何从Firebase中反转此列表的顺序？我想要最后一个项目是第一个。我试图使用 queryOrdered ，但是没有什么区别。我列出了一个从Firebase检索的数据结构示例：
- KhPRPQEOiVzPW7G2iQI：{
amount：20，
coordinate：{
lat：28.10388759332169，
long：-81.46038228976457
}，
creationTime ：2017-04-11 00:37:29 +0000，
creator：6MAK7nkzoBT6NzIxj7DW3564cf72，
description：搭便车，
distanceRadius：1609.34 ，
expireTime：2017-04-11 03:37:00 +0000，
paymentNonce：51df2b01-9e97-0fce-14d5-fc8fdf98603c，
provider ：PSEFUZdAAxRH14oYnyzE7yMpcil1，
status：accepted
}，
Code：
func retrieveRquestFromFir（）{
var searchType：String！
switch self.messageType {
case messageTypeEnum.creator：
searchType =creator
break
case messageEnum.provider：
searchType =provider
break
// TODO：在这里修复
let path =rquest / frontEnd / posts / userCreatedPost
self.childRef（path）.queryOrdered（byChild ：creationTime）.observe（.childAdded，with：{snapshot in
如果让snapDict = snapshot.value as？NSDictionary {
如果让postId = snapDict [searchType] as？String {
if postId == self.currentUserId（）！{
let rquestId = snapshot.key
let status = snapDict [status] as！String
//检查消息是否为等待或接受，以显示消息
如果状态==挂起||状态==接受{
让description = snapDict [description] as！字符串
让amount = snapDict [amount] as！字符串
让creator = snapDict [creator]为！字符串
var provider：String？
//计算到期时间
var expireTime：String！
让dateString = snapDict [expireTime] as！字符串
var date：Date！
if status ==pending{
date = Date（string：dateString，format：yyyy-MM-dd HH：mm：ss Z）！
如果日期< Date（）{
return
}
} else if status ==accepted{
expireTime = snapDict [expireTime] as！ String
date = Date（string：dateString，format：yyyy-MM-dd HH：mm：ss Z）！
}
如果让providerUser = snapDict [provider] as？字符串{
provider = providerUser
}
let array = [
expireTime：dateString，
amount：amount，
description：描述
rquestId：rquestId，
status：status，
provider：provider as Any，
creator：creator
] as NSDictionary
//检查日期是否超过5天，如果超过dont添加
let dateAmount = Date.daysBetween（start：date，end：Date（））
// let StringDate = newDate？.string（withFormat：yyyy-MM-dd HH：mm：ss Z）
if dateAmount< = 5 {
DispatchQueue.main.async {
self.RquestInfoArray.append（array）
self.tableView.reloadData（）
}
}
}
$ else {
DispatchQueue.main.async {
self.RquestInfoArray.append（array）
self.tableView.reloadData（）
}
$ b $ div class =h2_lin>解决方法正如@Frank所说，你需要排序你的结果客户端。
你可以用这样的排序数组 p>
let sorted = self.RquestInfoArray.sorted（by：{（r1：RequestInfoType，r2：RequestInfoType） - >
中的Bool返回r1.dateAmount> r2.dateAmount
））
但是如果你真的想要反转这个数组，简单一点就是在开始时添加你的新元素而不是结束。
$ p $ self $ R $ 0）
How can I reverse the order of this list in from Firebase? I want the last item to be the first. I tried to use queryOrdered, but that did not make a difference. I listed one sample of the data structure that I'm retrieving from Firebase:
"-KhPRPQEOiVzPW7G2iQI" : {
"amount" : "20",
"coordinate" : {
"lat" : 28.10388759332169,
"long" : -81.46038228976457
},
"creationTime" : "2017-04-11 00:37:29 +0000",
"creator" : "6MAK7nkzoBT6NzIxj7DW3564cf72",
"description" : "A ride ",
"distanceRadius" : 1609.34,
"expireTime" : "2017-04-11 03:37:00 +0000",
"paymentNonce" : "51df2b01-9e97-0fce-14d5-fc8fdf98603c",
"provider" : "PSEFUZdAAxRH14oYnyzE7yMpcil1",
"status" : "accepted"
},
Code:
func retrieveRquestFromFir(){
var searchType:String!
switch self.messageType {
case messageTypeEnum.creator:
searchType = "creator"
break
case messageTypeEnum.provider:
searchType = "provider"
break
}
//TODO: Fix here
let path = "rquest/frontEnd/posts/userCreatedPost"
self.childRef(path).queryOrdered(byChild: "creationTime") .observe(.childAdded, with: {snapshot in
if let snapDict = snapshot.value as? NSDictionary {
if let postId = snapDict[searchType] as? String {
if postId == self.currentUserId()! {
let rquestId = snapshot.key
let status = snapDict["status"] as! String
//check to see if message is pending or accepted in order to show messages
if status == "pending" || status == "accepted" {
let description = snapDict["description"] as! String
let amount = snapDict["amount"] as! String
let creator = snapDict["creator"] as! String
var provider:String?
// calculate expire time here
var expireTime:String!
let dateString = snapDict["expireTime"] as! String
var date:Date!
if status == "pending" {
date = Date(string: dateString, format: "yyyy-MM-dd HH:mm:ss Z")!
if date < Date() {
return
}
}else if status == "accepted" {
expireTime = snapDict["expireTime"] as! String
date = Date(string: dateString, format: "yyyy-MM-dd HH:mm:ss Z")!
}
if let providerUser = snapDict["provider"] as? String {
provider = providerUser
}
let array = [
"expireTime":dateString,
"amount":amount,
"description":description,
"rquestId":rquestId,
"status": status,
"provider":provider as Any,
"creator": creator
] as NSDictionary
//check if date is more than 5 days if it is more than dont Added
let dateAmount = Date.daysBetween(start: date, end: Date())
// let StringDate = newDate?.string(withFormat: "yyyy-MM-dd HH:mm:ss Z")
if dateAmount <= 5 {
DispatchQueue.main.async {
self.RquestInfoArray.append(array)
self.tableView.reloadData()
}
}
}
}
}else {
DispatchQueue.main.async {
self.RquestInfoArray.append(array)
self.tableView.reloadData()
}
}
}
})
}
解决方案
As @Frank says, you need to sort your results client-side.
You can either sort the array with something like this
let sorted = self.RquestInfoArray.sorted(by: { (r1: RequestInfoType, r2: RequestInfoType) -> Bool in
return r1.dateAmount > r2.dateAmount
})
but if you really just want to reverse the array, probably simpler just to add your new elements at the start instead of the end
self.RquestInfoArray.insert(contentsOf: array, at: 0)
这篇关于如何从Firebase逆转项目的顺序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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