Firebase 3 无法修改其他用户创建的数据

Question

在此应用程序中，每个用户都有一个 "votes" 计数器，但它仅在同一用户投票时有效，当另一个用户尝试在该引用中执行 FIRTransaction 时 returns nil。规则设置为任何用户。
当我需要 user2 更新 user1 "votes" 值时，它不会读取该键值来执行事务块，因此它 returns nil.

votesCountRef = ref.child("user1").child("votes")
votesCountRef.runTransactionBlock( { (currentData) -> FIRTransactionResult in
            let value = currentData.value! as! Int
            currentData.value = value + 1
            return FIRTransactionResult.successWithValue(currentData)
        })

结果：

Received votes actual value: Optional() Could not cast value of type 'NSNull' (0x110684600) to 'NSNumber' (0x10fce92a0).

但是当原始用户运行它时它会成功。

Json 用户 1 的树：

{ 
  "userUID" : "user1",
  "votes" : 2
}

数据库规则：

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

感谢@Frank，我可以这样管理它：

    ownerReceivedVotesCountRef.runTransactionBlock( { (currentData) -> FIRTransactionResult in

    let value = currentData.value as? Int ?? 0
    currentData.value! = (value as Int) + 1
    return FIRTransactionResult.successWithValue(currentData)
})

Answer 1

事务处理程序最初是运行客户端对当前值的最佳猜测。这通常是 nil，因此您的代码必须处理它。

来自Firebase documentation：

Note: Because runTransactionBlock:andCompletionBlock: is called multiple times, it must be able to handle nil data. Even if there is existing data in your remote database, it may not be locally cached when the transaction function is run, resulting in nil for the initial value.

像这样的东西应该适合你的情况：

let value = currentData.value as? Int ?? 0

Firebase 3 无法修改其他用户创建的数据

Firebase 3 can't modify other user created data

firebase

firebase-security

swift

firebase-realtime-database