Firestore 中的“querySnapshot.forEach 不是函数”

Question

我正在尝试对数据库进行查询，以获取子集合“角色”的所有文档以重定向到不同的路由。

let userRef1 = db.collection('users').doc(currentUser.uid).collection('roles')
let cont = 0
let rol = ''
let rolStatus = ''

userRef1.get().then(function(querySnapshot) {                                                                                                                               
  querySnapshot.forEach(function(doc) {                                                                                                                            

    cont++ 
    rol = doc.data().rol
    rolStatus = doc.data().status                                         
  });                                      

Answer 1

// Firebase App (the core Firebase SDK) is always required and must be listed first
import * as firebase from "firebase/app";
// Add the Firebase products that you want to use
import "firebase/auth";
import "firebase/firestore";
const firebaseConfig = {
  apiKey: "AIzaSyDNdWutrJ3Axpm-8ngNhzkzcw1g3QvkeFM",
  authDomain: "books-7bd8b.firebaseapp.com",
  databaseURL: "https://books-7bd8b.firebaseio.com",
  projectId: "books-7bd8b",
  storageBucket: "books-7bd8b.appspot.com",
  messagingSenderId: "385706228283",
  appId: "1:385706228283:web:a3c2c9585dd74d54693a1e",
};
firebase.initializeApp(firebaseConfig);
export const firebaseAuth = firebase.auth();
export const firestore = firebase.firestore();
export default firebase;

Answer 2

import { firestore } from "../../firebase";
export const loadCategories = () => {
  return (dispatch, getState) => {
    firestore
      .collection("CATEGORIES")
      .get()
      .then((querySnapshot) => {
        if (!querySnapshot.empty) {
          querySnapshot.forEach((doc) => {
            console.log(doc.id, "=>", doc.data());
          });
        }
      })
      .catch((error) => {
        console.log(error);
      });
  };
};

Answer 3

您应该在执行逻辑之前检查它是否始终存在：

userRef1.get().then(function(querySnapshot) { 

         if(querySnapshot)
         {
           querySnapshot.forEach(function(doc) { 
           
           ...you thing

         }                                                                                                                         
})     

Answer 4

不清楚你在用rol 和status 变量做什么。您已将它们声明为存储单个值，但您正在返回一个角色数组并遍历它们。

关于获取结果，如果您的浏览器支持 ES6，那么您可以执行以下操作：

let userRef1 = db.collection(`users/${currentUser.uid}/roles`)
let cont = 0
let rol;
let rolStatus;

return userRef1.get()
  .then(querySnapshot => {
    // Check if there is data
    if(!querySnapshot.empty) {
      // Create an array containing only the document data
      querySnapshot = querySnapshot.map(documentSnapshot => documentSnapshot.data());
      querySnapshot.forEach(doc => {
        let {rol, status} = doc;
        console.log(`rol: ${rol} - status: ${status}`);
      });
    } else {
      console.log('No data to show');
    }
  })
  .catch(err => {
    console.error(err);
  }); 

请注意：我只用 Node SDK 测试过这个

Answer 5

我有一组用户，包括uid，就像你的一样。对于每个用户，它都包含一个名为friends 的子集合。

目前，我正在为我的项目使用以下代码，没有任何问题。

module.exports = ({ functions, firestore }) => {
  return functions.firestore.document('/users/{uid}').onDelete((event) => {

    const userFriendsRef = getFriendsRef(firestore, uid);

     userFriendsRef.get().then(snapshot => {
       if (snapshot.docs.length === 0) {
         console.log(`User has no friend list.`);
         return;
      } else {
        snapshot.forEach(doc => {
          // call some func using doc.id
        });
      }
     }
  }
};

function getFriendsRef(firestore, uid) {
  return firestore.doc(`users/${uid}`).collection('friends');
}

尝试修复您的代码

db.collection('users').doc(currentUser.uid).collection('roles')

到

db.doc(`users/${currentUser.uid}`).collection('roles')