如何增加Cloud Firestore中的现有数字字段 [英] How to increment existing number field in Cloud Firestore

问题描述

我有一个字段，指示交易数量.交易发生后，我想将其增加1.我找不到任何直接执行此方法的方法.

I have a field which indicates the number of transactions. I would like to increment it by 1 as soon as a transaction occurs. I could'nt find any method to directly execute this.

一种方法是先获取用户，然后使用接收到的值+ 1更新该字段，但这太长且太慢.

One method is to get the user first and then update the field with the received value + 1, but this is too lengthy and slow.

有人可以告诉我其他可行的方法吗?

Can anyone tell me any other feasible method?

推荐答案

Firestore现在为此指定了一个特定的运算符FieldValue.increment().通过将此运算符应用于字段，该字段的值可以作为服务器上的单个操作来递增(或递减).

Firestore now has a specific operator for this called FieldValue.increment(). By applying this operator to a field, the value of that field can be incremented (or decremented) as a single operation on the server.

从Firebase文档上，在递增数值:

From the Firebase documentation on incrementing a numeric value:

var washingtonRef = db.collection('cities').doc('DC');

// Atomically increment the population of the city by 50.
washingtonRef.update({
    population: firebase.firestore.FieldValue.increment(50)
});

因此，无论当前值是多少，此示例都会将总体增加50.如果该字段尚不存在(或不是数字)，则在这种情况下将其设置为50.

So this example increments the population by 50, no matter what is current value is. If the field doesn't exist yet (or is not a number), it is set to 50 in this case.

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