在部署 Firebase 云函数时收到“每个都应该返回一个值或抛出”错误答案

【问题标题】：On Deploying the Firebase Cloud Function getting an error of "Each then should return a value or throw"在部署 Firebase 云函数时收到“每个都应该返回一个值或抛出”错误
【发布时间】：2020-01-22 17:15:54
【问题描述】：

我是 Cloud Functions 的新手，所以我在使用以下代码时遇到了问题，错误出现在最后提到 console.log 的部分，请协助我应该如何成功部署函数，因为我正在关注教程名称没有这样的错误。

'use-strict'

const functions = require('firebase-functions');
const admin = require("firebase-admin");

admin.initializeApp(functions.config().firebase);
exports.sendNotifications = functions.firestore.document("users/{user_id}/notifications/{notification_id}").onWrite(event => {


    const user_id = event.params.user_id;
    const notification_id = event.params.notification_id;




    return admin.firestore().collection("users").doc(user_id).collection("notifications").doc(notification_id).get().then(queryResult => {

        const from_user_id = queryResult.data().from;
        const message =  queryResult.data().message;

        const from_data = admin.firestore().collection("users").doc(from_user_id).get();
        const to_data = admin.firestore().collection("user").doc(user_id).get();

        return Promise.all([from_data, to_data]).then(result => {
            const from_name = result[0].data().name;
            const to_name = result[1].data().name;
            const token_id  = result[1].data().token_id;

            const payload  = {
                notification: {
                    title: "Notification from:" + from_name,
                    body: message,
                    icon: "default"


                }
            };

            return admin.messaging().sendToDevice(token_id, payload).then(result =>{

                console.log("notifcation sent");
            });

        });

    });




});

【问题讨论】：

标签： javascript android firebase google-cloud-firestore google-cloud-functions

【解决方案1】：

通过链接您的 Promises 并在最后一个 then() 中返回 null，如下所示，您应该可以解决您的问题：

exports.sendNotifications = functions.firestore.document("users/{user_id}/notifications/{notification_id}").onWrite(event => {

    const user_id = event.params.user_id;
    const notification_id = event.params.notification_id;

    return admin.firestore().collection("users").doc(user_id).collection("notifications").doc(notification_id).get()
        .then(queryResult => {

            const from_user_id = queryResult.data().from;
            const message = queryResult.data().message;

            const from_data = admin.firestore().collection("users").doc(from_user_id).get();
            const to_data = admin.firestore().collection("user").doc(user_id).get();

            return Promise.all([from_data, to_data]);
        })
        .then(result => {
            const from_name = result[0].data().name;
            const to_name = result[1].data().name;
            const token_id = result[1].data().token_id;

            const payload = {
                notification: {
                    title: "Notification from:" + from_name,
                    body: message,
                    icon: "default"

                }
            };

            return admin.messaging().sendToDevice(token_id, payload)

        })
        .then(messagingResponse => {
            console.log("notification sent");
            return null;   //Note the return null here, watch the 3 videos about "JavaScript Promises" from the Firebase video series: https://firebase.google.com/docs/functions/video-series/
        });

});

您可以查看相应的 MDN 文档：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises#Chaining

另外，请注意，在您的代码中，您似乎没有使用 to_name 常量。

【讨论】：