Firebase prevent duplicate categories using rule [duplicate]

问题

This question already has answers here:

Firebase how to prevent duplicate entries atomically (4 answers)

Closed 3 years ago.

Here is my database structure for categories

I want prevent duplicate data using Firebase rules

here is my firebase rule

 {
    "rules": {
    ".read": "auth != null",
    ".write": "auth != null",


    "categories": {
      "$catid": {

       ".validate": "!root.child(newData.child('type').val()).exists()"
      }
    }
} 
}

When I am trying to insert again java it's inserting duplicate of java

how do I prevent to insert duplicate category

回答1:

As per suggested by Frank van Puffelen

I have changed my data structure as following

and also updated Firebase rules as following

{
 "rules": {
   ".read": "auth != null",
   ".write": "auth != null",

 "categories": {
   "$categorie":{
        ".validate": "!data.exists()"
   }
 }
}
}

Now it's not inserting data if data is already there.

Thanks Frank van Puffelen

来源：https://stackoverflow.com/questions/39912201/firebase-prevent-duplicate-categories-using-rule