I encountered a problem in my chat app.

I works when I post message doc to the messages col but then I'm trying do getDocs back and render them I get an empty array.

I looked through FB docs, and I didn't notice any mistakes on my part. I also read an article where I was advised to use the react-firebase library with useCollectionData with which I had the same result.

const [messages, loading] = useCollectionData(
        firestore.collection('messages').orderBy('createdAt')
    )

I tried different approaches but nothing seems to work.

import React, { useState, useEffect } from 'react'
import { auth, db, app } from '../../firebase.config'
import { useAuthState } from 'react-firebase-hooks/auth'
import { useCollectionData } from 'react-firebase-hooks/firestore'
import { docs, onSnapshot, query, where, addDoc, collection, serverTimestamp, orderBy, getDocs } from 'firebase/firestore'

import Message from '../Message/Message'
import Spinner from '../Spinner/Spinner'
import './chat.css'


const Chat = () => {
  const [user, loading, error] = useAuthState(auth)
  const [value, setValue] = useState('')
  const [msgs, setMsgs] = useState([])

  console.log('msgs>>>>', msgs)

  useEffect(() => {
    const fetchMsg = async () => {
      const messagesRef = collection(db, 'messages')

      const q = query(
        messagesRef,
        orderBy('timestamp', 'desc')
      )

      const querySnap = await getDocs(q)

      let listings = []

      querySnap.forEach((doc) => {
        return listings.push({
          id: doc.id,
          data: doc.data(),
        })
      })
      setMsgs(listings)
    }
    fetchMsg()
  }, [])
  

  const sendMessage = async (e) => {
    e.preventDefault();

    const docRef = await addDoc(collection(db, 'messages'), {
      uid: user.uid,
      displayName: user.displayName,
      photoURL: user.photoURL,
      text: value,
      createdAt: serverTimestamp()
    })
    console.log(docRef)

    setValue('')
  }

  if (loading) {
    return <Spinner />
  }

  return (
    <>
      <div className='ch-wind'>
        {msgs.map((msg) => (
          <Message key={msg.id} msg={msg} style={{ backgroundColor: user.uid === msg.uid ? '#A32cc4' : '#a1045a' }} />
        ))}
      </div>

      <form className="ch-form" onSubmit={sendMessage}>
        <textarea
          value={value}
          className='ch-form-text'
          onChange={e => setValue(e.target.value)}
          placeholder='Enter your message here'
        />
        <button

          className='ch-form-btn'
        >
          Send
        </button>
      </form>
    </>
  )
}

export default Chat

CodePudding user response：

By using useEffect() hook, I would assume that you want to get the data realtime. Firestore has a realtime listeners that you can use. You can listen to a document with the onSnapshot() method. An initial call using the callback you provide creates a document snapshot immediately with the current contents of the single document. Then, each time the contents change, another call updates the document snapshot. See code below:

useEffect(() => {
  const messagesRef = query(collection(db, 'messages'), orderBy('timestamp', 'desc'));
  onSnapshot(messagesRef, (snapshot) => {
    // Maps the documents and sets them to the `msgs` state.
    setMsgs(snapshot.docs.map(doc => ({
      id: doc.id,
      data: doc.data()
    })))
  })
}, [])

Also, as pointed out by @CDoe, you should use the same Fieldname which you set from the addDoc method as you can see on the above code.

Then on the rendering, something like this:

{msgs.map((msg) => (
  // By setting the `doc.data()` to the object `data`, you should access it by `msg.data.<object_key>`
  <Message key={msg.id} msg={msg.data.text} style={{ backgroundColor: user.uid === msg.data.uid ? '#A32cc4' : '#a1045a' }} />
))}

I leave some comments on the code to better understand it.

For more information on realtime updates, you may check out this documentation.

CodePudding user response：

In the query, you're trying to orderBy timestamp. That's not a field you're creating in sendMessage.

When a value you're ordering by doesn't exist on the document, it won't return.

Maybe you meant to orderyBy the createdAt value.

const q = query(
  messagesRef,
  orderBy('createdAt', 'desc')
)