Firebase 嵌套解析 Swift

Question

我有以下 Firebase 查询用于解析到我的 tableView

{
  "-LC8fVE90ovEFRQAhhdv" : {
    "description" : "Bu grupta arkadaşlar takılsınlar",
    "members" : [ "VSVmIF4o0ie2QMIcXdTDTcC8Hq93", "hJgM5tYU45VmjaMTzYAG4Yo3RyD2", "YrLEyhWf9KOIwoK2YN7HrzxpwMc2" ],
    "title" : "Takılmaca"
  },
  "-LC8wUR-11bX5FnjQ6Mk" : {
    "description" : "Hello",
    "members" : [ "VSVmIF4o0ie2QMIcXdTDTcC8Hq93", "hJgM5tYU45VmjaMTzYAG4Yo3RyD2", "nkwPkD2FeDZZFDnLunTe3D2EuQr2", "YrLEyhWf9KOIwoK2YN7HrzxpwMc2" ],
    "messages" : {
      "-LC9Pj9krCB4kZnXtXc8" : {
        "content" : "Its me",
        "senderId" : "YrLEyhWf9KOIwoK2YN7HrzxpwMc2"
      },"-LC9Pj9krCB4kasfXtXc8" : {
        "content" : "Who are you",
        "senderId" : "YrLEyhWf9KOIwoK2YN7HrzxpwMc2"
      }
}

我正在尝试使用以下代码获取内容和 senderId

var groupMessages = [Message]()
REF_GROUPS.observeSingleEvent(of: .value) { (groups) in
    guard let groups = groups.children.allObjects as? [DataSnapshot] else { return }

    for group in groups {
        let groupss = group.value as? NSDictionary

        if let messages = groupss!["messages"] as? [String: Any] {

        }
    }            
    handler(groupMessages)
}

但是，我无法访问内容，因为消息对象是由随机标识符（如 LC9Pj9krCB4kZnXtXc8）创建的，如何获取该内容和 senderId？

Answer 1

第一件事永远不要在Swift 中使用NSDictionary 或NSArray，这会使事情变得复杂。其次，只需检查snapshot.exists() 而不是为allObjects 放置guard。

for group in groups 应替换为 for child in snapshot.children 并且 child 将是 DataSnapshot 本身。见以下代码：

REF_GROUPS.observeSingleEvent(of: DataEventType.value) { (snapshot) in
     if snapshot.exists() {
         var allMessages: Array<Dictionary<String, String>> = []
            for child in snapshot.children {
                let childSnapshot = child as! DataSnapshot
                guard let dictValue = childSnapshot.value as? Dictionary<String, Any>, let messages = dictValue["messages"] as? Dictionary<String, Any> else {continue}
                if let array = Array(messages.values) as? Array<Dictionary<String, String>> {
                    allMessages.append(contentsOf: array)
                }
            }

            /// All messages into single array
            print(allMessages)

            /// All senderIds
            let senderIds = allMessages.map({$0["senderId"]!})
            print(senderIds)

            /// Unique senderIds
            let uniqueSenderIds = Array(Set(senderIds))
            print(uniqueSenderIds)

            /// Grouping the senderId with messages
            var finalDict: Dictionary<String, [String]> = [:]
            for data in allMessages {
                guard let senderId = data["senderId"], let content = data["content"] else {continue}
                if var oldValue = finalDict[senderId] {
                    oldValue.append(content)
                }
                else {
                    finalDict[senderId] = [content]
                }
            }
            print(finalDict)

            /// Inbuilt Dictionary grouping function
            let dictionary = Dictionary(grouping: allMessages, by: {$0["senderId"]!})
            print(dictionary)
}

输出：所有消息

[["content": "Its me", "senderId": "YrLEyhWf9KOIwoK2YN7HrzxpwMc2"],["content": "Who are you", "senderId": "YrLEyhWf9KOIwoK2YN7HrzxpwMc2"]]

输出：senderIds

["YrLEyhWf9KOIwoK2YN7HrzxpwMc2", "YrLEyhWf9KOIwoK2YN7HrzxpwMc2"]

输出：uniqueSenderIds

["YrLEyhWf9KOIwoK2YN7HrzxpwMc2"]

输出：finalDict

["YrLEyhWf9KOIwoK2YN7HrzxpwMc2": ["Its me", "Who are you"]]

输出：finalDict

["YrLEyhWf9KOIwoK2YN7HrzxpwMc2": [["content": "Its me", "senderId": "YrLEyhWf9KOIwoK2YN7HrzxpwMc2"], ["content": "Who are you", "senderId": "YrLEyhWf9KOIwoK2YN7HrzxpwMc2"]]]

我不确定你为什么要获取所有组的内容，但我想建议通过Groups -> GroupId -> messages ref 获取数据并为此 ref 设置一个侦听器，以便在收到新消息时通知应用程序.