Saving Day to Firestore for the first time only in flutter

July 26, 2023

After registering as a member of firebase, you are also trying to add data to the firestore
The code is as follows

await FirebaseFirestore.instance.collection('users').doc(FirebaseAuth.instance.currentUser!.uid).set({
        '1_email' : FirebaseAuth.instance.currentUser!.email,
        '2_name' : 'Null',
        '3_phone' : '01012345678',
        '4_age' : 20,
        }
      );

I want the data to be stored in the firestore only for the first time
So I tried to code it as follows, but I couldn’t solve it

if(FirebaseFirestore.instance.collection('users').doc(FirebaseAuth.instance.currentUser!.uid) == null){
      await FirebaseFirestore.instance.collection('users').doc(FirebaseAuth.instance.currentUser!.uid).set({
        '1_email' : FirebaseAuth.instance.currentUser!.email,
        '2_name' : 'Null',
        '3_phone' : '01012345678',
        '4_age' : 20,
        }
      );
    }

What I thought was that if a document such as user uid is null in the fireestore, I added data, and if it is not null, I wrote a code in the form of leaving it alone, but I couldn’t solve it

>Solution :

This line is meaningless:

if(FirebaseFirestore.instance.collection('users').doc(FirebaseAuth.instance.currentUser!.uid) == null){

You’re checking whether a document reference is null, which is will never be. What you want to do, is check whether the document exists, for which you will have to try and read it from the database.

var ref = FirebaseFirestore.instance.collection('users').doc(FirebaseAuth.instance.currentUser!.uid);
var snapshot = await ref.get();
if(!snapshot.exists){
  ...
}