Is it possible to access the subcollection of the collection on Cloud Firestore triggers via the callback's snapshot parameter?

user_2338858 0
Viewed 116

Let's say, I need to send an email to all the members of the group when the group is complete:

export const sendEmailToNewMember = functions.firestore.document('group/{groupId}').onCreate(async (snapshot,context) => {
}

The collection group has subcollection members. I check if the member's count has incremented and matches the total number of members who can join a group. If the final member has joined, I need to send all the members an email saying the group is complete.

The data structure looks like the one shown below:

collection group {
  membersCount: 9999,
  totalMembers: 100000,
  ....

  users subcollection
}

I tried accessing the collection through ref like so:

const usersRef = snap.ref.collection('users)

But, the result was undefined. For now, I access it using

await firestore().collection('group').doc(groupId).collection('users')

Is it possible to access the subcollection without awaiting it and from the snapshot itself?

google-cloud-functions google-cloud-firestore firebase node.js javascript
1 Answers

The document() takes path to a document and not a field. So if you want to trigger this function when any of the fields in group document is updated then set the path to .document('group/{groupId}').

Also snapshot in onCreate() will then contain data of that group's document only (the document that triggered the function). You'll have to explicitly read the sub-collection.

It seems you want to send email to new member that joins a group. You can instead trigger the function when a new user is added in user's sub-collection as shown below:

// Here user's UID would be ID of sub-document
export const sendEmailToNewMember = functions.firestore.document('group/{groupId}/users/{userId}').onCreate(async (snapshot,context) => {
  const { groupId, userId } = context.params;
}
user_131306970
Related