如何设置“主键”在Firebase中？

问题描述

这是我计划在留言板应用程序中创建自己的留言板的模式：

  { 
board：{
jane-board：{
 //元信息，比如谁创建了这个板子
}，
john-board：{ 
 //元信息，比如谁创建了这个板子
}，
 ... 
}，
jane-board：{
 // data 
}，
john-board：{
 // data 
} 
} 
  

确保boards的规则不能包含两个 jane-board？

我试过写规则，但是失败：

  {
rules：{
.read：true，
boards：{
写：真，
$ board_name：{
.validate：！newData.parent（）。hasChild（$ board _name）
} 
} 
} 
} 
  

解决方案

由于您使用板的名称作为存储它的关键，所以已经保证每个板名最多可以存在一次。

你试图完成什么并不完全清楚。但是，如果您试图阻止董事会的数据被覆盖，您可以通过以下方式来完成：

  {
rules：{
.read：true，
boards：{
$ board_name：{
.write： ！data.parent（）。hasChild（$ board_name）
} 
} 
} 
} 
   b 
 $ b 
您的规则发生了变化：
 
 
 
 
我删除了 .write：true  from  boards 。有了这个规则，每个人都可以阅读所有板，因为你。      c $ c>规则，因为它更像是阻止写入而不是验证结构 
 
我检查新电路板是否已经存在于 current 数据中。您正在检查 newData ，但是没有任何意义：新电路板将始终存在于新数据中。
 
 
 
This is the schema I plan to have for my message board app where users can create their own message boards:  
{
    "boards" : {
        "jane-board" : {
            // meta information like who created this board
        },
        "john-board" : {
            // meta information like who created this board
        },
        ...
    },
    "jane-board" : {
        // data
    },
    "john-board" : {
        // data
    }
}  
What would be the rule to ensure that "boards" cannot contain two "jane-board"?  
I tried writing a rule but it fails:  
{
    "rules" : {
        ".read" : true,
        "boards" : {
            ".write" : true,
            "$board_name" : {
                ".validate" : "!newData.parent().hasChild($board_name)"
            }
        }
    }
}  
 解决方案 
Since you are using the board's name as the key to store it under, there is already a guarantee that each board name can exist at most once.
It is not entire clear what you're trying to accomplish. But if you are trying to prevent a board's data from being overwritten, you can accomplish that with:
{
    "rules" : {
        ".read" : true,
        "boards" : {
            "$board_name" : {
                ".write" : "!data.parent().hasChild($board_name)"
            }
        }
    }
}  
Changes for your rules:
I removed the ".write": true from boards. With that rule in place everyone can read all boards, since you cannot take permissions away on a lower level.
I changed the rule to a ".write" rule, since it feels more like preventing a write than validating structure
I check whether the new board already exists in the current data. You were checking in newData, but that doesn't make any sense: the new board will always exist in the new data.
                        
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