如何编写规则以防止从数据库中删除节点 [英] How to write a rule to prevent any deletion of node from database

问题描述

我正在尝试编写规则来保护数据库.但是我对编写一条规则感到困惑，该规则将阻止从数据库中删除任何节点.我已经阅读了有关newData.exists的信息，但是当我尝试在模拟器中运行它时，删除成功！由于可以通过将节点的值设置为null来删除该节点，因此我尝试将node的值模拟为null并成功完成，这是不希望的.

I am trying to write rules to secure database. But I am confused on writing a rule which will prevent from deleting any node from database. I have read regarding newData.existsbut when I tried running it in simulator deletion was succeeded! As a node can be deleted by setting its value to null, so I tried simulating the value of node to null and it was successful, which was not desired.

假设我有这个节点:

root{
Number of Users:20
}

我写了这些规则:

"Number of Users":{
".read":true,
 ".write":"auth!==null && newData.exists()"
 }

如果我有任何错误，请纠正我.

Am I making any mistake, please correct me.

推荐答案

要允许添加新节点，但要防止删除或覆盖任何节点:

To allow adding new nodes, but prevent deleting or overwriting any node:

".write": "!data.exists()"

要允许添加和覆盖(但不能删除)任何节点，

To allow adding and overwriting, but not deleting, any node:

".write": "newData.exists()"

更新:这些规则的模拟器屏幕截图

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