从Firebase取回 [英] Retrieve from Firebase

问题描述

我创建了一个Firebase数据库，并使用Push（）方法将数据保存到数据库中。这工作正常。但是，我面临的这个问题是当我检索数据。由于Push（）通过创建一个临时密钥来工作，我不知道如何进入该树的子进程，使用orderByValue（）进行排序。我的JSON如下所示：

  {
videos：{
videoId1：{
-KhxlA5-yIHYq-7PQC84：{\url \：\testUrl1 \，\title \：\test1 \，\x \： -  3.9357306957244875，\y \：6.528204441070557，\z \：2.5558924674987795，\time \：7982.197021484375}，
-KhxlAEpJp30xF5n6kc5：{ \ url\：\ testUrl2\，\ title\：\ test2\，\ x\：4.0330400466918949，\ y\： 6.52820348739624，\z\：2.3994064331054689，\time \：2637.8599853515625}，
-KhxlAPyGEI7AxFssG_：{\url \：\testUrl3 \ \ title\：\ test3\，\ x\： -  3.446043014526367，\ y\：6.52820348739624，\ z\： -  3.1854910850524904，\\ \\time \：5350.770263671875}
} 
} 
} 
  

我的要求是我需要基于th对其进行排序e 时间键，同时检索数据。

我可以到达 videoId1 树，但不知道如何超越。 （使用 reference.Child（videos）。Child（videoUrl））

谢谢。

解决方案

您正在为 videoId1 下的每个子项存储一个字符串值。没有办法有效地查询该字符串内。

如果您想要在这些子项下进行查询，请确保将数据存储为JSON，以便总计树变成：

  {
videos：{
videoId1：{
-KhxlA5-yIHYq-7PQC84：{
url：testUrl1，
title：test1，
x：-3.9357306957244875，
y：6.528204441070557，
z 2.5558924674987795，
time：7982.197021484375 
} 
，
-KhxlAEpJp30xF5n6kc5：{
url：testUrl2，
title ：test2，
x：4.0330400466918949，
y：6.52820348739624，
z：2.3994064331054689，
time：2637.8599853515625 
} 
，
-KhxlAPyaGEI7AxFssG_：{
url：testUrl3，
title：test3，
x：-3.446043014526367 ，
y：6.52 820348739624，
z：-3.1854910850524904，
time：5350.770263671875 
} 
} 
} 
} 
  
 
 $ b $ p 
 $ b pre 
 
 
 code> ref.child（'videos / videoId1'）。orderByChild（'time'）... 
  

I have created a Firebase DB and I'm using the Push() method to save data into the DB. This works fine. But this issue I'm facing is when I retrieve the data. As Push() works by creating a temporary key, I don't know how to step into the child of that tree to perform sorting using orderByValue(). My JSON looks like this:

{
  "videos" : {
    "videoId1" : {
      "-KhxlA5-yIHYq-7PQC84" : "{\"url\":\"testUrl1\",\"title\":\"test1\",\"x\":-3.9357306957244875,\"y\":6.528204441070557,\"z\":2.5558924674987795,\"time\":7982.197021484375}",
      "-KhxlAEpJp30xF5n6kc5" : "{\"url\":\"testUrl2\",\"title\":\"test2\",\"x\":4.0330400466918949,\"y\":6.52820348739624,\"z\":2.3994064331054689,\"time\":2637.8599853515625}",
      "-KhxlAPyaGEI7AxFssG_" : "{\"url\":\"testUrl3\",\"title\":\"test3\",\"x\":-3.446043014526367,\"y\":6.52820348739624,\"z\":-3.1854910850524904,\"time\":5350.770263671875}"
    }
  }
}

My requirement is that I need to sort it based on the time key while retrieving the data.

I can reach until the videoId1 tree but don't know how to get past that. (Using reference.Child ("videos").Child (videoUrl))

Thanks.

解决方案

You're storing a string value for each child under videoId1. There is no way to usefully query inside that string.

If you want to query under those children, make sure to store the data as JSON, so that the total tree becomes:

{
  "videos": {
    "videoId1": {
        "-KhxlA5-yIHYq-7PQC84": {
            "url": "testUrl1",
            "title": "test1",
            "x": -3.9357306957244875,
            "y": 6.528204441070557,
            "z": 2.5558924674987795,
            "time": 7982.197021484375
        }
        ",
        "-KhxlAEpJp30xF5n6kc5": {
            "url": "testUrl2",
            "title": "test2",
            "x": 4.0330400466918949,
            "y": 6.52820348739624,
            "z": 2.3994064331054689,
            "time": 2637.8599853515625
        }
        ",
        "-KhxlAPyaGEI7AxFssG_": {
            "url": "testUrl3",
            "title": "test3",
            "x": -3.446043014526367,
            "y": 6.52820348739624,
            "z": -3.1854910850524904,
            "time": 5350.770263671875
        }
    }
  }
}

With that you can query as Kirill suggested:

ref.child('videos/videoId1').orderByChild('time')...

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