CODEWITHSUNDEEP
reactjsfirebasegoogle-cloud-firestoregoogle-cloud-functions
S.W.
S.W.

Reputation: 115

How to make Firebase function return realtime snapshot

My firebase function returns a result from the query but it doesn't update if the db changes. How can I update it to return realtime updates? I tried putting an observer in the function but it only fires once.

getCurrentMessage.js // firebase function

const admin = require('../variables').admin

module.exports = async (req, res) => {
  const db = admin.firestore()
  const now = new Date()
  const timestampNow = now / 1000
  const location = req.query.location

  try {
    const messagesRef = db.collection('messages')
    const snapshot = await messagesRef
      .where('displayTo', '>=', timestampNow)
      .where('location', '==', location)
      .get()
    if (snapshot.empty) {
      console.log('No matching documents.')
      return res.status(404).send(`No current message found.`)
    }
    snapshot.forEach((doc) => {
      if (doc._fieldsProto.displayFrom.integerValue <= timestampNow) {
        return res.status(200).send(doc) // return 1st to match
      } else {
        return res.status(404).send('No current message found.')
      }
    })
  } catch (e) {
    console.log(`Error: ${e.message}`)
  }
}

the function call

    // get current message
    axios
      .get(`${dir}/getCurrentMessage?location=${location}`)
      .then((res) => {
        this.setState({
          customMessage: res.data,
        })
      })
      .catch((e) => {
        console.log(`Error: ${e.message}`)
      })

Upvotes: 1

Views: 140

Answers (1)

Doug Stevenson
Doug Stevenson

Reputation: 317352

What you're trying to do isn't possible with Cloud Functions. Cloud Functions can only return a single response to the client. It can't send multiple responses, nor can it stream results to the client. Once you call send() on the response object, the request is terminated and can do nothing else.

If you want the client to receive realtime updates, then it should either query the database directly, or you should use a backend that supports websockets or some other streaming technology.

Upvotes: 2

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