如何为每个集合插入添加时间戳，如何在Cloud Functions中更新Firestore数据库 [英] How to add timestamp to every collection insert,update in Cloud Functions for firestore database

问题描述

我有一个名为Posts的Firestore集合 我在客户端插入了一个插件，就可以了.

I have a firestore collection called Posts I make an insert on the client side and it works.

我想使用firebase函数将createdAt和updatedAt字段添加到我的帖子集合firestore中的每个插入中.

I want to add the createdAt and updatedAt fields to every insert in my posts collection firestore using firebase functions.

推荐答案

要通过Cloud Function向Post记录添加createdAt时间戳，请执行以下操作:

In order to add a createdAt timestamp to a Post record via a Cloud Function, do as follows:

exports.postsCreatedDate = functions.firestore
  .document('Posts/{postId}')
  .onCreate((snap, context) => {
    return snap.ref.set(
      {
        createdAt: admin.firestore.FieldValue.serverTimestamp()
      },
      { merge: true }
    );
  });

为了将modifiedAt时间戳添加到现有的Post，您可以使用以下代码. 但是，每次发布文档的某个字段发生更改(包括对createdAt和updatedAt字段的更改，以无限循环结束)时，都会触发此Cloud Function. strong> ....

In order to add a modifiedAt timestamp to an existing Post you could use the following code. HOWEVER, this Cloud Function will be triggered each time a field of the Post document changes, including changes to the createdAt and to the updatedAt fields, ending with an infinite loop....

exports.postsUpdatedDate = functions.firestore
  .document('Posts/{postId}')
  .onUpdate((change, context) => {
    return change.after.ref.set(
      {
        updatedAt: admin.firestore.FieldValue.serverTimestamp()
      },
      { merge: true }
    );
  });

因此，您需要比较文档的两种状态(即change.before.data()和change.after.data())，以检测更改是否涉及的字段不是createdAt或updatedAt.

So you need to compare the two states of the document (i.e. change.before.data() and change.after.data() to detect if the change is concerning a field that is not createdAt or updatedAt.

例如，假设您的Post文档仅包含一个字段name(不考虑两个时间戳字段)，则可以执行以下操作:

For example, imagine your Post document only contains one field name (not taking into account the two timestamp fields), you could do as follows:

exports.postsUpdatedDate = functions.firestore
  .document('Posts/{postId}')
  .onUpdate((change, context) => {
    const newValue = change.after.data();
    const previousValue = change.before.data();

    if (newValue.name !== previousValue.name) {
      return change.after.ref.set(
        {
          updatedAt: admin.firestore.FieldValue.serverTimestamp()
        },
        { merge: true }
      );
    } else {
      return false;
    }
  });

换句话说，恐怕您必须逐字段比较两个文档状态....

In other words, I'm afraid you have to compare the two document states field by field....

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