AngularFire2 - Append to list child - firebase

Question

I'm trying to add an object to /users/[userKey]/invitedTo but set deletes the existing data, so does update.
What I want to end up with is something like this:
users
-uniqueuserkey
--name: Name
--InvitedTo
---eventuniquekey1
----eventname: event name 1
----etc
---eventuniquekey2
----eventname: event name 2
----etc
-
// this.event.push(eventObj);
this.event.push(eventObj).then((item) => {
if (item) {
const itemKey = item.key;
for (const key in guests) {
if (guests.hasOwnProperty(key)) {
const invitedObj = {};
const invitedTo = this.db.object(`/users/${key}/invitedTo`);
invitedObj[itemKey] = eventObj;
invitedTo.set( { invitedObj } );
}
}
}
});
Update does exactly what I need, but it also deletes existing value:
for (const key in guests) {
if (guests.hasOwnProperty(key)) {
const invitedObj = {};
invitedObj[itemKey] = eventObj;
this.users.update(key, { invitedTo: invitedObj });
}
}
Should I just get the existing data and add to it?

Answer 1

If you want to add an object, you (usually) should use the push method instead of set or update:
const invitedTo = this.db.list(`/users/${key}/invitedTo`);
invitedTo.push(eventObj);
That way, Firebase will create a unique key and add it to the invitedTo node.
If you want to set the key yourself, then you could use the update method like this:
const invitedTo = this.db.object(`/users/${key}/invitedTo/${itemKey}`);
invitedTo.update(eventObj);