如何从Firebase逆转项目的顺序

如何从Firebase中撤消此列表的顺序？ 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" : "A ride ", "distanceRadius" : 1609.34, "expireTime" : "2017-04-11 03:37:00 +0000", "paymentNonce" : "51df2b01-9e97-0fce-14d5-fc8fdf98603c", "provider" : "PSEFUZdAAxRH14oYnyzE7yMpcil1", "status" : "accepted" }, 

码：

 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() } } } }) } 

Answer 1

正如@Frank所说，你需要对客户端的结果进行sorting。

你可以用这样的东西sorting数组

 let sorted = self.RquestInfoArray.sorted(by: { (r1: RequestInfoType, r2: RequestInfoType) -> Bool in return r1.dateAmount > r2.dateAmount }) 

但如果你真的只是想扭转数组，可能更简单，只是在开始而不是结束时添加新的元素

 self.RquestInfoArray.insert(contentsOf: array, at: 0)