如何增加 Firebase 中的记录? [英] How to increment a record in Firebase?

问题描述

我有每个用户的 Firebase 记录搜索:0".在某些事件中，我想在当前计数上加 1.我已经走了这么远，但由于某种原因，它不起作用:

I have a Firebase record "searches: 0" for each user. On some event, I'd like to add 1 to what the current count is. I've gotten this far, but for some reason, it's not working:

du.fbAddSearchCount = function() {
    var usr = new Firebase(firebase_url + "/users/" + user_uid);

    usr.on("value", function(snapshot) {
        user = snapshot.val();

       var usersRef = ref.child("users");

       var fbUser = usersRef.child(user_uid);
       fbUser.update( {
           searches: user.searches + 1
       });
    }
}

有什么帮助可以让它工作吗?

Any help to get this working?

谢谢.

推荐答案

firebase JavaScript SDK v7.14.0 中有一个新方法 ServerValue.increment()

There's a new method ServerValue.increment()in firebase JavaScript SDK v7.14.0

因为不需要往返，所以性能更好，更便宜.

It's better for performance and cheaper since no round trip is required.

请参阅此处

添加了 ServerValue.increment() 以支持没有事务的原子字段值增量.

Added ServerValue.increment() to support atomic field value increments without transactions.

API 文档此处

使用示例:

firebase.database()
    .ref('users')
    .child(user_uid)
    .child('searches')
    .set(firebase.database.ServerValue.increment(1))

或者你可以递减，只需将 -1 作为函数 arg 像这样:

Or you can decrement, just put -1 as function arg like so:

firebase.database()
    .ref('users')
    .child(user_uid)
    .child('searches')
    .set(firebase.database.ServerValue.increment(-1))

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