访问 doc.id in.onWrite firebase 云 function

Question

I'm triggering a cloud function with onWrite. Within the onWrite function, I want to do something with the ref ID of the document that was written. How can I grab this? My current code looks something like this, but I don't know how to fill eventID.

exports.syncEvents = functions.firestore
    .document('events/{eventID}')
    .onWrite((change, context) => {

admin.firestore().collection('users').doc(host).collection('events').doc(eventID).set({
            active: true
          })
        });

Answer 1

change.after is a DocumentSnapshot of the document that changed, after it was written. DocumentSnapshot has a property called id that contains the id of the document. So change.after.id is the document id.

Answer 2

The context object contains the params of the query. In your example, the context object will look like this:

{
 ...
 params: {
   eventID: "whatever-eventId-is"
 }
 ...
}

So you just call get it from the context:

const eventId = context.params.eventId;

Here is more about context: https://firebase.google.com/docs/reference/functions/cloud_functions.eventcontext