解决一堆承诺时出现 Firebase 错误：无法将未定义或 null 转换为对象

Question

我在运行云功能时遇到来自 firebase 的错误：

FIREBASE 警告：用户回调引发了异常。类型错误： 无法将 undefined 或 null 转换为对象

这是一个可能发生错误的sn-p：

    // const functions = require('firebase-functions');
    // const admin = require('firebase-admin');
    // const underscore = require('underscore');
    // admin.initializeApp(functions.config().firebase);
    // export updateSimilars = functions.database.ref('...').onWrite(event => {
    ...
        for (var i in callerFlattenLikesDislikes) {
            getOtherUsersPromises.push(getOtherUsersFromName(callerFlattenLikesDislikes[i], genre));
        }    
        console.log('getOtherUsersPromises length: ' + getOtherUsersPromises.length);    
        return Promise.all(getOtherUsersPromises).then(dataArr => {
                    console.log(dataArr); // will never fire
                    dataArr.forEach(data => {
                        data.forEach(user => {
                            if (otherUsers.indexOf(user) > -1 && user !== userId) {
                                otherUsers.push(user);
                            }
                        });
                    });
             ....
             ....

      function getOtherUsersFromName(name, genre) {
       console.log('fired getOtherUsersFromName: ' + name);
       return new Promise((resolve, reject) => {
        admin
            .database()
            .ref('/names/' + genre + '/' + name)
            .once('value', snapshot => {
                var dic = snapshot.val();
                var dislikingUsers = Object.keys(dic['dislikingUsers']);
                var likingUsers = Object.keys(dic['likingUsers']);
                var users = underscore.union(dislikingUsers, likingUsers);
                console.log('will resolve: ' + users);
                resolve(users);
            });
         });
       }

基本上，我有一组要异步执行的承诺（多个输入项的相同 firebase 查询）。 我想在开始处理之前收集所有结果。

但是Promise.all 之后的.then 似乎永远不会被解雇，而且我有以下firebase 日志：

有人帮我吗？

谢谢！

Answer 1

我认为您需要检查路径 '/names/' + genre + '/' + name 中是否存在名称。此路径为空时会报错。

function getOtherUsersFromName(name, genre) {
       console.log('fired getOtherUsersFromName: ' + name);
       return new Promise((resolve, reject) => {
        admin
            .database()
            .ref('/names/' + genre + '/' + name)
            .once('value', snapshot => {
               if (snapshot.exists()){
                var dic = snapshot.val();
                var dislikingUsers = Object.keys(dic['dislikingUsers']);
                var likingUsers = Object.keys(dic['likingUsers']);
                var users = underscore.union(dislikingUsers, likingUsers);
                console.log('will resolve: ' + users);
                resolve(users); 
               } else {
                  // Do something as the path is empty
               }
            });
         });
       }