How to delete a document in Firestore using cloud functions

Question

I want to check documents as they are created in firestore to ensure there are no swear words contained in a publicly visible field. I would like to be able to delete the post after it has been detected to contain swear words. To do this I am trying to use firebase cloud functions:

// Package used to filter profanity
const badWordsFilter = require('bad words-list');

// The Cloud Functions for Firebase SDK to create Cloud Functions and setup triggers.
const functions = require('firebase-functions');

// The Firebase Admin SDK to access Cloud Firestore.
const admin = require('firebase-admin');
admin.initializeApp();

export const filterBadWords =
  functions.firestore.document("posts/{userId}/userPosts/{postId}").onCreate((snapshot, context) => {
    const message = snapshot.data.val();

    // Check if post contains bad word
    if (containsSwearwords(message)) {
      //This is where I want to remove the post.
      //What do I put here to delete the document?
    }
  })

// Returns true if the string contains swearwords.
function containsSwearwords(message: any) {
  return message !== badWordsFilter.clean(message);
}

Database structure:

-posts(Collection)
   |
   +---{userID} (Document)
          |
          +---userPosts (collection)
                  |
                  +---{Documents to be checked} (Document)
                  |
                  +-Url1(field)
                  +-Url2(field)
                  +-string1(field)<- check this field for swear
                  +-string2(field)<- check this field for swear

The cloud functions are written using javascript

Modern versions of the firebase-functions library do not deliver something called event to the first argument of an onCreate function. They deliver a document snapshot as shown in the documentation. If you're using an old version, it's really old, and you should upgrade. firebase.google.com/docs/functions/… — Doug Stevenson
– Doug Stevenson, Commented Oct 30, 2020 at 20:46
are you using web, swift, objective-c, java android, kotlin/KTX android, java, python, or go? — Baby_Boy
– Baby_Boy, Commented Dec 1, 2020 at 19:03
@Baby_Boy I am using swift, but the functions are written in javascript — David
– David, Commented Dec 1, 2020 at 19:04

Poul Kruijt · Accepted Answer · 2020-12-01 19:10:18Z

2

+50

You can just use the ref to get the DocumentReference and call delete():

functions.firestore.document("posts/{userId}/userPosts/{postId}").onCreate(
  async (snapshot, context) => {
    const message = snapshot.data.val();

    // Check if post contains bad word
    if (containsSwearwords(message)) {
      await snapshot.ref.delete();
    }
  }
)

If they can edit their post afterwards, you should generalize this functionality and add it to the onUpdate trigger as well

answered Dec 1, 2020 at 19:10

Poul Kruijt

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5 Comments

David Over a year ago

This looks like what I am looking for but I get the error error Parsing error: Unexpected token snapshot

Poul Kruijt Over a year ago

the snapshot is the property you get in your onCreate listener

David Over a year ago

Yes, I see that I have it just the way you have it there. I am troubleshooting now.

David Over a year ago

Nevermind, was missing the async. Works now. will award bounty when I can

Poul Kruijt Over a year ago

@Bjorn good to see it works. And yes, I should have mentioned i used the async/await pattern there :)

Baby_Boy · Accepted Answer · 2020-12-01 19:24:37Z

0

This answer is going to be short, but it doesn't require an explanation. Here's the code (for swift, I'm not 100% sure how to do this in js)

swift:

db.collection("cities").document("DC").delete() { err in
    if let err = err {
        print("Error removing document: \(err)")
    } else {
        print("Document successfully removed!")
    }
}

this might work for javascript, not 100% sure

db.collection("cities").doc("DC").delete().then(function() {
    console.log("Document successfully deleted!");
}).catch(function(error) {
    console.error("Error removing document: ", error);
});

hope it helps

edited Dec 1, 2020 at 19:24

answered Dec 1, 2020 at 19:12

Baby_Boy

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