TypeError：NULL不是对象（评估＆＃x27; documentsnapshot.exists＆＃x27;）

Question

我有一个组件ShowReportCount，当我使用auth（）。签名（）;登录时会引发错误，它给我带来以下错误：

typeError：null不是对象（评估 'documentsnapshot.exists'）

console.log（'uid：'，user.uid）返回：

**UID:** lzDbqczG5yXaMJRzHZO3VQEOD0n2

console.log（'dbuser：'，dbuser）返回：

**dbUser:** {"_documentPath": {"_parts": ["users", "lzDbqczG5yXaMJRzHZO3VQEOD0n2"]}, "_firestore": {"_app": {"_automaticDataCollectionEnabled": true, "_deleteApp": [Function bound deleteApp], "_deleted": false, "_initialized": true, "_name": "[DEFAULT]", "_nativeInitialized": true, "_options": [Object]}, "_config": {"ModuleClass": [Function FirebaseFirestoreModule], "hasCustomUrlOrRegionSupport": false, "hasMultiAppSupport": true, "namespace": "firestore", "nativeEvents": [Array], "nativeModuleName": [Array], "statics": [Object], "version": "10.5.1"}, "_customUrlOrRegion": undefined, "_nativeModule": {"RNFBFirestoreCollectionModule": true, "RNFBFirestoreDocumentModule": true, "RNFBFirestoreModule": true, "RNFBFirestoreTransactionModule": true, "clearPersistence": [Function anonymous], "collectionGet": [Function anonymous], "collectionOffSnapshot": [Function anonymous], "collectionOnSnapshot": [Function anonymous], "disableNetwork": [Function anonymous], "documentBatch": [Function anonymous], "documentDelete": [Function anonymous], "documentGet": [Function anonymous], "documentOffSnapshot": [Function anonymous], "documentOnSnapshot": [Function anonymous], "documentSet": [Function anonymous], "documentUpdate": [Function anonymous], "enableNetwork": [Function anonymous], "getConstants": [Function anonymous], "setLogLevel": [Function anonymous], "settings": [Function anonymous], "terminate": [Function anonymous], "transactionApplyBuffer": [Function anonymous], "transactionBegin": [Function anonymous], "transactionDispose": [Function anonymous], "transactionGetDocument": [Function anonymous], "waitForPendingWrites": [Function anonymous]}, "_referencePath": {"_parts": [Array]}, "_transactionHandler": {"_firestore": [Circular], "_pending": [Object]}}}

任何人都可以为我提供解决这个问题的解决方案？

ShowReportcount.js

import React, { useContext, useState } from 'react';
import { Text, View } from 'react-native';
import firestore from '@react-native-firebase/firestore';

import styles from './ShowReportCount.styles';
import { UserContext } from '../../../context/UserContext';

const db = firestore();

export default function ShowReportCount(type) {
    const [count, setCount] = useState(0);
    const [user, setUser] = useContext(UserContext);

    console.log('UID:', user.uid);
    const dbUser = db.collection('users').doc(user.uid);
    console.log('dbUser:', dbUser);

    dbUser.onSnapshot(
        {
            includeMetadataChanges: true,
        },
        (documentSnapshot) => {
            if (documentSnapshot.exists) {
                if (type.type === 'exercise') {
                    setCount(documentSnapshot.data().exerciseCount);
                    return;
                }

                if (type.type === 'workout') {
                    setCount(documentSnapshot.data().workoutCount);
                    return;
                }
            } else {
                console.log("error: document doesn't exist");
            }
        }
    );

    return (
        <View>
            <Text style={styles.statCardNumber}>{count.toString()}</Text>
        </View>
    );
}

Answer 1

如果在快照上发生错误，则会发生这种情况。确保用户在其上具有认证的对象。要查看快照上发生的错误，请提供错误处理程序作为第二个参数onsnapshot。请参阅下面的示例代码：

    dbUser.onSnapshot(
        {
            includeMetadataChanges: true,
        },
        (documentSnapshot) => {
            if (documentSnapshot.exists) {
                if (type.type === 'exercise') {
                    setCount(documentSnapshot.data().exerciseCount);
                    return;
                }

                if (type.type === 'workout') {
                    setCount(documentSnapshot.data().workoutCount);
                    return;
                }
            } else {
                console.log("error: document doesn't exist");
            }
        }, (error) => {
           // Catch errors from `onSnapshot`.
           console.log(error);
    });

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