因此，我需要从 firebase 集合中获取具有给定 id 的数据。然后我的函数应该返回它（文档），并且在我的测试中它应该打印（作为“结果”）。出于某种原因，我的测试打印了“未定义”，但我的函数 (getIteration(id)) 准确地打印出我需要它返回的内容（在返回上方的 console.log 中）。为什么它返回 undefined 但使用相同的 doc.data() 打印我需要的内容？这是我的代码：//gets the iteration with the given idasync function getIteration(id) { fb.db.collection('iteration').where('id', '==', id).get().then(snapshot => { snapshot.forEach(doc => { console.log(doc.data()) return doc.data(); }) })}和我的测试：firebase.getIteration(fbIterationID).then(function(result){ console.log('LOGGING FB ITERATION DOCUMENT WITH THE ID OF: ' + fbIterationID) console.log(result)})
3 回答
慕仙森
TA贡献1827条经验 获得超7个赞
//gets the iteration with the given id
async function getIteration(id) {
return fb.db.collection('iteration').where('id', '==', id).get().then(snapshot => {
return snapshot.docs.map(doc => doc.data());
})
}
慕田峪9158850
TA贡献1794条经验 获得超7个赞
import React, {useEffect, useLayoutEffect, useState} from 'react'
import {View, Text, StyleSheet, SafeAreaView, ScrollView, TouchableOpacity } from 'react-native'
import { Avatar } from 'react-native-elements/dist/avatar/Avatar';
import CustomListItem from '../../components/CustomListItem'
import { auth, db } from '../../services/firebase';
import {SimpleLineIcons} from '@expo/vector-icons'
export default function HomeScreen({ navigation }) {
const [chats, setChats] = useState([]);
const [userInfo, setUserInfo] = useState([])
const [isDms, setIsDms] = useState(true);
useEffect(() => {
function unsubscribeDms(){
db.collection('chats').onSnapshot(snapshot => {
snapshot.docs.map(doc => {
if (doc.data().isDM == true){
if (doc.data().users[0] == auth.currentUser.uid){
setChats(chats => [...chats, {id: doc.id, data: doc.data(), otherUser: doc.data().users[1]}])
db.collection("users").doc(doc.data().users[1]).get().then((doc) => {
setUserInfo(userInfo => [...userInfo, {uid: doc.id, data: doc.data()}]
)
})
}
else if (doc.data().users[1] == auth.currentUser.uid){
setChats(chats => [...chats, {id: doc.id, data: doc.data(), otherUser: doc.data().users[0]}])
db.collection("users").doc(doc.data().users[0]).get().then((doc) => {
setUserInfo(userInfo => [...userInfo, {uid: doc.id, data: doc.data()}]
)
})
}
}
})
})}
async function unsubscribeGcs(){
await db.collection('chats').onSnapshot(snapshot => {
snapshot.docs.forEach(doc => {
if (doc.data().isDM == false){
var allUsers = doc.data().users
if (allUsers.includes(auth.currentUser.uid)){
setChats(chats => [...chats, {id: doc.id, data: doc.data()}])
}
}
})
})
}
if (isDms){
unsubscribeDms()
}
else {
unsubscribeGcs()
}
}, [])
function getphotoUrl(uid){
//return JSON.stringify(userInfo[0])
return userInfo.length
if (userInfo.length > 0){
var picInfo = userInfo.filter((value) =>{
return value.uid == uid
})[0].uid
//})[0].data.photoURL
return picInfo
}
else {
return 'null'
}
}
function getDisplayName(uid){
//return JSON.stringify(userInfo[0])
return userInfo.length
if (userInfo.length > 0){
var nameInfo = userInfo.filter((value) =>{
return value.uid == uid
})[0].uid
//})[0].data.displayName
console.log("this is the display name" + nameInfo)
return nameInfo
}
else {
return 'null'
}
}
function signOutUser(){
auth.signOut().then(() => {
navigation.replace('Login')
})
}
useLayoutEffect(() => {
navigation.setOptions({
title: "Chats",
headerRight: () => (
<View style={{
flexDirection: "row",
justifyContent: "space-between",
width: 80,
marginRight: 20
}}>
<View style={{marginLeft: 20}}>
<TouchableOpacity onPress={() => navigation.navigate("Profile", {currentUser: auth.currentUser})} activeOpacity={0.5}>
<Avatar rounded source={{ uri: auth?.currentUser?.photoURL }}/>
</TouchableOpacity>
</View>
<TouchableOpacity onPress={() => navigation.navigate("AddChat")}>
<SimpleLineIcons name="pencil" size={24} color="black"></SimpleLineIcons>
</TouchableOpacity>
</View>
)
});
}, [navigation])
function enterChat(id, chatName, photo){
navigation.navigate("Chat", {
id: id,
chatName: chatName,
photo: photo
})
}
return (
<SafeAreaView>
<ScrollView style={styles.container}>
{chats.map(({id, data, otherUser}) => (
<CustomListItem key={id} id={id} enterChat={enterChat} photo={getphotoUrl(otherUser)} userName={getDisplayName(otherUser)} isDm={data.isDM}/>
))}
</ScrollView>
</SafeAreaView>
)
}
const styles = StyleSheet.create({
container: {
height: "100%"
}
})
斯蒂芬大帝
TA贡献1827条经验 获得超8个赞
您需要从那里返回承诺，getIteration以便调用者可以使用其结果。使函数异步不会为您做到这一点：
async function getIteration(id) {
return fb.db...
}
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