访问 Firebase 中的用户 uid

Question

我有这个 JSON 结构：

     {
"Devices" : {
"1EJ8QmEQBJfBez7PMADbftCjVff1" : {
  "Device1" : {
    "Category" : "Others",
    "Description" : "",
    "DeviceName" : "",
    "ImageUrl" : ""
  },
  "Device2" : {
    "Category" : "Chairs",
    "Description" : "",
    "DeviceName" : "",
    "ImageUrl" : ""
  },
  "Device3" : {
    "Category" : "Others",
    "Description" : "",
    "DeviceName" : "",
    "ImageUrl" : ""
  }
},
"97PUAcUC5UYxLpBOLnC4yQjxiEf2" : {
  "Device1" : {
    "Category" : "Others",
    "Description" : "",
    "DeviceName" : "",
    "ImageUrl" : ""
  },
  "Device2" : {
    "Category" : "Books",
    "Description" : "",
    "DeviceName" : "",
    "ImageUrl" : ""
  },
  "Device3" : {
    "Category" : "Chairs",
    "Description" : "",
    "DeviceName" : "",
    "ImageUrl" : ""
    }
   }
  },
 "UserProfile" : {
"1EJ8QmEQBJfBez7PMADbftCjVff1" : {
  "city" : "",
  "email" : "",
  "name" : "",
  "phone" : ""
},
"97PUAcUC5UYxLpBOLnC4yQjxiEf2" : {
  "city" : "",
  "email" : "",
  "name" : "",
  "phone" : ""
   },
 }
}

我想访问每个设备中的类别节点？ 那可能吗？ 因为我想检索所有具有相同类别的节点的数据！

let ref = FIRDatabase.database().reference().child("Devices")

    ref.queryOrderedByChild("Category")

我已尝试访问设备！然后直接进入类别！ 看来这不是正确的方法！

别告诉我我需要改变 JSON 的结构！

有什么方法可以访问用户ID吗？

Answer 1

在 NoSQL 数据库中，您通常必须针对应用所需的用例对数据进行建模。使用您当前的数据结构，您可以有效地加载用户的设备。

为了还有效地允许加载某个类别的设备，您还必须存储该信息。这是一种方法：

"Categories": {
  "Others": {
    "1EJ8QmEQBJfBez7PMADbftCjVff1_Device1": "1EJ8QmEQBJfBez7PMADbftCjVff1/Device1",
    "1EJ8QmEQBJfBez7PMADbftCjVff1_Device3": "1EJ8QmEQBJfBez7PMADbftCjVff1/Device3",
    "97PUAcUC5UYxLpBOLnC4yQjxiEf2_Device1": "97PUAcUC5UYxLpBOLnC4yQjxiEf2/Device1"
  },
  "Chairs": {
    "1EJ8QmEQBJfBez7PMADbftCjVff1_Device2": "1EJ8QmEQBJfBez7PMADbftCjVff1/Device2",
    "97PUAcUC5UYxLpBOLnC4yQjxiEf2_Device3": "97PUAcUC5UYxLpBOLnC4yQjxiEf2/Device3"
  },
  "Books": {
    "97PUAcUC5UYxLpBOLnC4yQjxiEf2_Device2": "97PUAcUC5UYxLpBOLnC4yQjxiEf2/Device2"
  }

}

所以上面的结构使用<uid>_<devicekey>作为键，然后将/devices下的那个项目的路径作为它的值。

我建议在NoSQL data modeling 上阅读这篇精彩的文章。