CODEWITHSUNDEEP
javascriptfirebasereact-nativefirebase-realtime-database
Sumanth Jois
Sumanth Jois

Reputation: 3234

Firebase database delete all nodes equalTo a particular value

I have a list of users, which contains a node called scannedCards, which contains an array of cardIds. Below is a screenshot of one user.

Below is a screenshot of one user

There are multiple users like above, I want to delete all the card Ids if they are equalTo(Some Card Id), I want to this with all the users at once.

Below is the query I a using:

  const ref = database.ref('users');
  const query = ref.orderByChild('cardId').equalTo(cardId);

But the result is always empty, Can someone please tell how I can achieve this?

Upvotes: 1

Views: 878

Answers (1)

Pat Needham
Pat Needham

Reputation: 5918

The query you listed above doesn't seem to be returning anything because, based on the screenshot provided, cardId isn't a direct child property of users, but rather a property of each object under the scannedCards list that users may have.

If you only need to do this as part of a one-time operation, you may run something like this:

const ref = database.ref('users');
ref.once('value').then(snapshot => {
  const users = snapshot.val();
  for (var user_id in users) {
    const scannedCards = users[user_id].scannedCards;
    for (var card in scannedCards) {
      if (scannedCards[card].card_id == "<some card id>") {
        firebase.database().ref(`users/${user_id}/scannedCards/${card_id}`)
        .set(null);
      }
    }
  }
});

If you plan on letting logged-in users delete their scanned cards, it would be a little bit less complicated:

// user_id is for whoever is logged in
const ref = firebase.database().ref(`users/${user_id}/scannedCards`);
ref.once('value').then(snapshot => {
  const scannedCards = snapshot.val();
  for (var card in scannedCards) {
    if (scannedCards[card].card_id == "<some card id>") {
      firebase.database().ref(`users/${user_id}/scannedCards/${card_id}`)
      .set(null)
    }
  }
});

Also worth pointing out, scannedCards is not an array of card ids, because the keys are object ids and the values are objects (which contain cardId and userId properties).

Upvotes: 5

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