add a property to a created object (Firebase Functions)

问题

I'm hooking to the creation of objects on a specific collection (orders) I need to add a new property to the object before it's saved, not returning anything, to no avail.

I have looked at the documentation at https://firebase.google.com/docs/reference/functions/functions.firestore.DocumentBuilder#writing_data but it's for onUpdate so it doesn't work as i intend it.

exports.createOrder = firestore.document('orders/{orderId}').onCreate((snap, context) => {
  const newOrder = snap.data()
  console.log('triggered', newOrder)
  const orderId = randomize('A0', 10)
  console.log({ orderId })
  return newOrder.ref.set({ orderId }, { merge: true })
  //newOrder.ref.set is undefined
  return newOrder.set({ orderId }, { merge: true })
  //newOrder.set is undefined
})

回答1:

snap.data() returns a raw JavaScript object whose properties contain the values of the fields in the document. It does not contain a property called ref (unless you had a document field also called ref).

If you need to write back to the document that changed, use the DocumentReference type object provided in snap.ref. See also the API documentation for the DocumentSnapshot type object passed to the function.

snap.ref.set(...)

来源：https://stackoverflow.com/questions/58312876/add-a-property-to-a-created-object-firebase-functions