Firebase 云函数 - snapshot.forEach(...).then 不是 function

Question

我的数据库布局是：

@posts
   @postId_abc
     -total_score: ... // will update from cloud function
     -score_count: ... // will update from cloud function

@scores
   @postId_abc
      -uid_1: 10
      -uid_2: 20
      _uid_3: 50

每当用户设置分数时，我想使用cloud function将分数参考中的所有分数相加，并将它们设置为该特定帖子的total_score属性。 当我尝试以下代码时，出现错误：

FIREBASE WARNING: Exception was thrown by user callback. TypeError: snapshot.forEach(...).then is not a functio FIREBASE WARNING: Exception was thrown by user callback. TypeError: snapshot.forEach(...).then is not a functio funcio and Exception from a finished function: TypeError: snapshot.forEach(...).then is not a function

看来我的snapshot.forEach((child) => {... }).then(() => {不起作用，但scoreCountProperty.set(...)确实增加了。

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

exports.updateScore = functions.https.onCall((data, response) => {

    const postId = data.postId;

    const postsRef = admin.database().ref('/posts/' + postId);
    const scoreCountProperty = admin.database().ref('/posts/' + postId + '/' + 'score_count');

    var totalScore = 0.0;

    admin.database().ref('scores').child(postId).once('value', snapshot => {

    if (snapshot.exists()) {

        snapshot.forEach((child) => {

            totalScore += child.val()

        })
        .then(() => { 
                
            console.log('totalScore: ', totalScore);

            return postsRef.set({ "total_score": totalScore });       
        })
        .then(() => { 
                
            return scoreCountProperty.set(admin.database.ServerValue.increment(1));                
        })
        .catch((error) => {
            console.log('ERROR - updateScore Failed: ', error);
        });
    });
});

Answer 1

正如错误消息所述， Snapshot.forEach()不会返回您可以调用then()的 object 。 事实上，我很确定它什么也没有返回。

但是无论如何您都不需要then() ，因为Snapshot.forEach()不是同步操作。

所以这应该是你想要的：

snapshot.forEach((child) => {
    totalScore += child.val()
})
console.log('totalScore: ', totalScore);

return postsRef.set({ "total_score": totalScore }).then(() => { 
    return scoreCountProperty.set(admin.database.ServerValue.increment(1));                
})
.catch((error) => {
    console.log('ERROR - updateScore Failed: ', error);
});