尽管同一模型在另一个文件中工作，但我收到“User.findOne 不是函数”错误消息。 类似的问题答案不起作用

Question

First time posting on here, FYI.

Below is my "User" model in its own file. I create the schema and assign it. When I go to use this model in my authRoutes file it works fine just as you'd imagine. But when I use an identical import in one of my screen files I receive the "User.findOne is not a function" error message (linked below).

I am using this method to find a user in the database in order to access it's attributes. I have tried using the module.exports way of exporting the model and also trying to use require() as the import statement...neither has fixed my issue...been stuck on this for a while some insight would be great! (Hopefully this was clear, let me know)

"User.findOne is not a function..."

models/User.js

const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
    email: {
        type: String,
        unique: true,
        required: true
    },
    password: {
        type: String,
        required: true
    },
    balance: {
        type: Number,
        default: 100,
    }
});

mongoose.model('userSchema', userSchema);

routes/authRoutes.js (Works here)

const mongoose = require('mongoose');
const User = mongoose.model('userSchema');

const express = require('express');
const router = express.Router();
//const User = require('../models/User');
const jwt = require('jsonwebtoken');



router.post('/signup', async (req, res) => {
    const {email, password} = req.body;

    try {
        const user = new User({email, password});
        await user.save();

        const token = jwt.sign({ userId: user._id}, 'SOME_SECRET_KEY');
        res.send({token});
    } catch (err) {
        return res.status(422).send(err.message);
    }

});

router.post("/signin", async (req, res) => {
    const {email, password} = req.body;

    if (!email || !password) {
        return res.status(422).send({error: "Must provide email and password."});
    }

    const user = await User.findOne({ email });

    if (!user) {
        return res.status(422).send({ error: "Invalid email or password"});
    }

    try {
        //await user.comparePassword(password);

        const token = jwt.sign({userId: user._id}, "SOME_SECRET_KEY");
        res.send({token, email});
    } catch (err) {
        return res.status(422).send({ error: "Invalid email or password"});
    }
})

screens/SomeScreen.js (Does NOT work here, error)

import React, {useContext, useState} from 'react'
import {View, StyleSheet, Text, ScrollView, TextInput, Button} from 'react-native';
//import { LinearGradient } from 'expo-linear-gradient';
import colors from '../../constants/colors';
import RecieverCard from '../../components/RecieverCard';
import HistoryCard from '../../components/HistoryCard';
import {Provider, Context} from "../context/AuthContext";
import AsyncStorage from "@react-native-async-storage/async-storage";

const mongoose = require('mongoose');
const User = mongoose.model('userSchema');

const getUserBalance = async (userEmail) => {
    let user;

    try {
        user = await User.findOne(userEmail);

    } catch(err) {
        console.log(err);
    }
    return user;
};

Answer 1

require is not a React api, and so it will not work in your frontend.

You should use that in your node.js backend.

Regardless, why would you use mongoose & models in your frontend? I suggest you make an endpoint / controller responsible of getting the user balance in your backend, and then simply send a request to your backend and await for the response data.