是否可以在本機反應中從另一個 class 組件訪問 useRef 變量？

Question

我正在嘗試訪問在 class 組件中的功能組件中聲明的 useRef 變量。 這可能嗎？ 目前，當我在我的 class 組件 FireMessage 中導入功能組件 DetailsScreen 時，並在 get db() function 中添加 console.log(DetailsScreen.receiverUid) 它返回“未定義”。 您知道是什么原因造成的，以及如何在 class 組件中訪問此變量嗎？

**DetailsScreen**


import 'react-native-gesture-handler';

import { Image, StyleSheet, Text, TouchableOpacity, View, ScrollView, 
SafeAreaView, FlatList, Alert, TouchableHighlight, Platform, Dimensions, 
Linking} from 'react-native';

import React, {useState, useContext, useRef} from 'react';


const DetailsScreen = ({route, navigation}) => {

    const receiverUid = useRef(route.params.key);
}


export default DetailsScreen;


**FireMessage**

import firebase from "firebase";
import firebaseConfig from './firebaseConfig.js';
import 'react-native-gesture-handler';
import * as React from 'react';
import DetailsScreen from './DetailsScreen.js';

class FireMessage {

 constructor() {
   this.init()
   this.checkAuth() 
 }

 init = () => {
   if (!firebase.apps.length && firebaseConfig.apps.length === 0) {
   firebase.initializeApp({
    apiKey: "xxxxxxxxxxx",
    authDomain: "xxxxxxxxxxx",
    databaseURL: "xxxxxxxxxx",
    projectId: "xxxxxxxx",
    storageBucket: "xxxxxxxxxx",
    messagingSenderId: "xxxxxxxx",
    appId: "xxxxxxxxxxx",
    measurementId: "xxxxxxxxx"
   });
  }
};

checkAuth = () => {
  firebase.auth().onAuthStateChanged(user => {
    if (!user) {
      firebase.auth().signInAnonymously();
    }
  });
};

send = messages => {
  messages.forEach(item => {
    const message = {
      text: item.text,
      timestamp: firebase.database.ServerValue.TIMESTAMP,
      user: item.user
    };

   this.db.push(message)
 });
};

parse = message => {
   const { user, text, timestamp } = message.val();
   const { key: _id } = message;
   const createdAt = new Date(timestamp);


   return {
    _id,
    createdAt,
    text,
    user
   };
};

get = callback => {
   this.db.on("child_added", snapshot => 
   callback(this.parse(snapshot)));
};

off() {
   this.db.off();
}

get db() {
   console.log(DetailsScreen.receiverUid)
   return firebase.database().ref("messages");
}

get uid() {
   return (firebase.auth().currentUser || {}).uid;
}
}

export default new FireMessage();

Answer 1

每當你更新receiverUid更新DetailsScreen.receiverUid

const newId = 'some-receiver-id'
receiverUid.current = newId
DetailScreen.receiverUid = newId