Firebase云函数报错：get.then不是函数，求助实现评论通知功能

Hey there! Let's break down what's causing this error and fix it right away.

The Root Cause #

That error pops up because you're missing parentheses after the get method. In Firestore, get() is an asynchronous function that returns a Promise—you need to call it (with parentheses) before you can chain .then() to handle the result. Without the parentheses, you're trying to access a then property on the function itself, which doesn't exist.

Corrected Code Example #

Here's how to fix your sendNotification function, with the missing parentheses added and a complete implementation to send the notification:

'use strict';
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.sendNotification = functions.firestore
  .document('Users/{userID}/Notifications/{notificationID}')
  .onCreate(async (snapshot, context) => {
    // Get the notification data from the new document
    const notificationData = snapshot.data();
    const userID = context.params.userID;

    try {
      // Fetch the user's device token - notice the parentheses after get()
      const userDoc = await admin.firestore()
        .collection('users')
        .doc(userID)
        .get(); // <-- This is where you were missing parentheses

      if (!userDoc.exists) {
        console.log(`User ${userID} not found`);
        return;
      }

      const userData = userDoc.data();
      const deviceToken = userData.deviceNotificationToken;

      if (!deviceToken) {
        console.log(`User ${userID} has no device token`);
        return;
      }

      // Prepare the notification payload
      const payload = {
        notification: {
          title: 'New Comment',
          body: notificationData.commentText || 'You received a new comment',
          sound: 'default'
        }
      };

      // Send the notification
      await admin.messaging().sendToDevice(deviceToken, payload);
      console.log('Notification sent successfully');
    } catch (error) {
      console.error('Error sending notification:', error);
    }
  });

Key Notes #

• Always use parentheses when calling Firestore asynchronous methods like get(), set(), update(), etc.—these are functions, not properties.
• If you prefer using .then() chains instead of async/await, you can adjust that part like this:

  admin.firestore()
    .collection('users')
    .doc(userID)
    .get() // <-- Parentheses here!
    .then(userDoc => {
      // Handle the user document data
    })
    .catch(error => {
      // Handle errors
    });
  

内容的提问来源于stack exchange，提问作者Mahmoud Eidarous