Check if a document exists in Firebase Firestore, if not create a new

Question

How do I check if a document exists in Firebase Firestore, if not create a new one.

this is my code for now:

create(doc: any, collection: string): any {
  this.db.collection(collection, ref => ref.where('nome', '==', doc.nome))
    .snapshotChanges()
    .subscribe((ref: any) => {
      console.log('Ref = ', ref);
      if (ref.length <= 0) {
        this.db.collection(collection).add({ ...doc }).then(
          res => console.log('Inserido com sucesso : ', res)
        ).catch(err => console.log('Erro : ', err));
      }
      else {
        console.log('Evento ja existe : ', ref);
      }
    }).unsubscribe();
}

Answer 1

Did you consider using the doc.nome value as the document ID? If you do that, you won't need to use a query to find a document for the value, and can use a transaction to check-and-write atomically:

1. Start the transaction
2. Read the document
3. If it doesn't exist yet, write the document
4. Commit the transaction

Also see:

• Can we not query collections inside transactions?