Question

在Firebase中具有以下结构：

-events
     -Firebase Push ID for Event 1
         **-key: "DF2342"**
         -name: "Event 1"
         -createdOn : 12/12/12
     -Firebase Push ID for Event 2
         **-key: "AB1232"**
         -name: "Event 1"
         -createdOn : 12/12/12

每个密钥都由运行应用程序的设备在本地自动生成（DF2342和AB1232），但我想先在设备上生成密钥，然后检查密钥是否已存在于firebase数据库中。如果确实存在，请重新生成密钥并重试。这里是我用的代码：

 let boardKey = self.keyGenHelper.generateUniqueKey()
        var validData = false
        while(!validData){
        databaseRef?.child("events").queryOrdered(byChild: "key").queryEqual(toValue: boardKey).observeSingleEvent(of: .childAdded, with: { (snapshot) in
            if !snapshot.exists() {
                let boardIdRef = self.databaseRef!.child("events").childByAutoId()
                boardIdRef.setValue(board.generateDictionary(key: boardKey))
                completion(boardKey, boardIdRef.key)
                validData = true
            }
        }, withCancel: {(error) in
            print(error)
        })
        }

这里的问题是while循环一直在继续，并且从未得到firebase的响应。对我来说，完成这项任务的最佳方法是什么？

Answer 1

由于您的应用程序要求您不能使用childByAutoId，因此确保生成唯一ID的方法是在firebase中仅存储您生成的ID的附加表。例如：

def bricks(small,big,goal):

    current_lenght = 0
    current_value = 5
    number_of_bricks = big
    builder(current_lenght,current_value,number_of_bricks,goal)
    current_value = 1
    print("in bricks", current_lenght)
    number_of_bricks = small
    builder(current_lenght,current_value,number_of_bricks,goal)
    if current_lenght == goal:
        return True
    else:
        return False

def builder(current_lenght,current_value,number_of_bricks,goal):

    use_count = 1
    while (goal - current_lenght) >+ current_value and use_count <= number_of_bricks:
        current_lenght += current_value
        print("in while ",current_lenght)
    print(current_lenght)
    return current_lenght

然后，当您生成密钥时，您可以执行以下操作：

"keys": {
  "DF2342": true,
  "AB1232": true,
  ...
}

您还需要确保将新生成的密钥写入let boardKey = self.keyGenHelper.generateUniqueKey() var validData = false while(!validData){ // check /keys in the database to see if we've already generated a key of this value databaseRef?.child("keys").queryEqual(toValue: boardKey).observeSingleEvent(of: .childAdded, with: { (snapshot) in if !snapshot.exists() { let boardIdRef = self.databaseRef!.child("events").childByAutoId() boardIdRef.setValue(board.generateDictionary(key: boardKey)) completion(boardKey, boardIdRef.key) validData = true } }, withCancel: {(error) in print(error) })。

Firebase独特价值

1 个答案: