Firebase子孩子已删除

Question

Is there any way to get if subchild removed. db structure is:

users:{
  a: {
    friends: {
      b:Jhon,
      c:Ted
  },
  b: { 
    friends: {
      a: Tom
    }
  },
  c: {
    friends:{
      a: Tom
    }
  }
}

I want get event while anybody removes any child from friends. Attaching event to every user is not a good way.
I am trying in node.js admin

Answer 1

Here is another way, you can create a special node for "friend removal request", so the client only writes to this node, then the server handles the deletion.

First, look at this database structure

{
    users: {
        a: {
            friends: {
                b:Jhon,
                c:Ted
            },
        }
        b: { 
            friends: {
                a: Tom
            }
        },
        c: {
            friends:{
                a: Tom
            }
        }
    }
    friend_removal_request : {
        <push_id>: {
            first_user: a,
            second_user: b
        }
    }
}

• The server attach child_added listener to friend_removal_request
• If a user wants to delete a friend of their, their client writes a new entry (by using DatabaseReference.push() method) to friend_removal_request . first_user is the user's id, second_user is their friend's id
• Then the listener at the server will be fired, the server now can proceed to delete their friendship by setting a null value (or call remove() ) to /users/$first_user/friends/$second_user and /users/$second_user_user/friends/$first_user
• After the friendship is deleted, the server deletes that request snapshot.ref.remove()

Now, the listener is only attached to a node.

This is my idea, let me know if you have another concern with this method. Hope this helps :)