Delete item from subcollection array in Firestore Firebase

Question

I am trying to delete item from array in profile collection named items subcollection. Function should be triggered whenever item is deleted from main items collection. Problem with below function is that when triggered it deletes all items from profile instead of deleted one only. How I could iterate over items array and perform check of deleted item id.

exports.updateDeletedItemOnProfile = functions.firestore
.document('items/{itemId}')
.onDelete((snap, context) => {
    const { itemId } = context.params
    const deletedItem = snap.data()

      
    if(deletedItem){
      db.collection('profiles')
        .doc(deletedItem.user.id)
        .update({
          items: admin.firestore.FieldValue.delete({
              id: itemId,
              title: deletedItem.title,
              price: deletedItem.price,
              image: deletedItem.image
          })
        })
      }
    return true
})

Doug Stevenson · Accepted Answer · 2020-05-28 22:36:30Z

1

onDelete triggers only fire when an entire document was deleted. By this time, it's too late - the document is simply gone. Something chose to delete it, and you won't be able to tell what did that.

If you want a function to trigger when any part of a document is modified, you should use an onUpdate trigger instead. That will give you the entire contents of the document before and after the change. You will have to compare them to figure out what specifically changed.

answered May 28, 2020 at 22:36

Doug Stevenson

321k37 gold badges458 silver badges474 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Katarzyna Gołek · Accepted Answer · 2020-05-28 23:28:37Z

I 've also tried onUpdate trigger for deleting data along with onWrite trigger to listen for any change when data is changed, however in both cases it does not give me any result for part referring to deleting data. Items subcollection in profiles collection remains unchanged. I am not sure where error in function lies, function execution does not show any error, finishes with status Ok....

exports.updateDeletedItemOnProfile = functions.firestore
.document('items/{itemId}')
.onUpdate((change, context) => {
  const { itemId } = context.params
  const beforeItem = change.before.data()
  const updatedItem = change.after.data()

    if (updatedItem === null) {
    

    return db.collection('profiles')
      .doc(beforeItem.user.id)
      .delete({
        items: admin.firestore.FieldValue.arrayRemove({
          id: itemId,
          title: beforeItem.title,
          price: beforeItem.price, 
          image: beforeItem.image,
          status: beforeItem.status,
        })
      })
    }  
    return true

})

exports.updateDeletedItemOnProfile = functions.firestore
.document('items/{itemId}')
.onUpdate((change, context) => {
  const { itemId } = context.params
  const beforeItem = change.before.data()
  const updatedItem = change.after.data()

    if (updatedItem === null) {
    

    return db.collection('profiles')
      .doc(beforeItem.user.id)
      .update({
        items: admin.firestore.FieldValue.delete({
          id: itemId,
          title: beforeItem.title,
          price: beforeItem.price, 
          image: beforeItem.image,
          status: beforeItem.status,
        })
      })
    }  
    return true

})

Collectives™ on Stack Overflow

Delete item from subcollection array in Firestore Firebase

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related