Cloud Firestore Swift：如何删除文档查询

Question

I would like to delete all documents in my collection Usernames that has the field UID as the current user's ID. This is my code so far:

let uid = Auth.auth().currentUser!.uid
db.collection("Usernames").whereField("UID", isEqualTo: uid).delete

but here comes the error:

Value of type 'Query' has no member 'delete'.

Any special technique to this? Thanks!

Answer 1

The guide shows you how to delete data. It also notes that deleting entire collections shouldn't be done from the client. There's no way to delete from a query -- you will have to get all the documents and delete them individually. If there is the potential for lots of documents, then you should do this server-side. If you know for sure there will only be a few, you can query them, get the doc references, and then delete them, like this:

let uid = Auth.auth().currentUser!.uid
db.collection("Usernames").whereField("UID", isEqualTo: uid).getDocuments() { (querySnapshot, err) in
  if let err = err {
    print("Error getting documents: \(err)")
  } else {
    for document in querySnapshot!.documents {
      document.reference.delete()
    }
  }
}

If this is something that will need to be done frequently, then this is a good opportunity to examine your data structure. Maybe make a collection where user's Usernames are listed under their uid . Then you could just query that single doc and use it to reference the other ones to delete.

Usernames: {
   byUID: {
        uid1: {
            funky_monkey: true,
            goodTimes: true
        }
   }
   byUsername: {
        funky_monkey: {
            UID: uid1
        }
   }
}

This is just one suggestion. There are definitely other options that may be better for your app.