Flutter firestore - Check if document ID already exists

Question

I want to add data into the firestore database if the document ID doesn\'t already exists. What I\'ve tried so far:

// varuId == the ID that is set to the do         


        

Answer 1

  QuerySnapshot qs = await Firestore.instance.collection('posts').getDocuments();
  qs.documents.forEach((DocumentSnapshot snap) {
    snap.documentID == varuId;
  });

getDocuments() fetches the documents for this query, you need to use that instead of document() which returns a DocumentReference with the provided path.

Querying firestore is async. You need to await its result, otherwise you will get Future, in this example Future<QuerySnapshot>. Later on, I'm getting DocumentSnapshots from List<DocumentSnapshots> (qs.documents), and for each snapshot, I check their documentID with the varuId.

So the steps are, querying the firestore, await its result, loop over the results. Maybe you can call setState() on a variable like isIdMatched, and then use that in your if-else statement.

Edit: @Doug Stevenson is right, this method is costly, slow and probably eat up the battery because we're fetching all the documents to check documentId. Maybe you can try this:

  DocumentReference qs =
      Firestore.instance.collection('posts').document(varuId);
  DocumentSnapshot snap = await qs.get();
  print(snap.data == null ? 'notexists' : 'we have this doc')

The reason I'm doing null check on the data is, even if you put random strings inside document() method, it returns a document reference with that id.

Answer 2

To check if document exists in firestore. Trick use .exists method

Firestore.instance.document('collection/$docId').get().then((onValue){
onValue.exists ? //exists : //not exist ;
});

Answer 3

Use the exists method on the snapshot:

final snapShot = await Firestore.instance.collection('posts').document("docID").get();

   if (snapShot.exists){
        //it exists
   }
   else{
        //not exists 
   }

Answer 4

You can get() the document and use the exists property on the snapshot to check whether the document exists or not.

An example:

final snapShot = await Firestore.instance
  .collection('posts')
  .document(docId)
  .get()

if (snapShot == null || !snapShot.exists) {
  // Document with id == docId doesn't exist.
}